Patent Publication Number: US-2015079457-A1

Title: Lithium-ion secondary battery, and method of producing the same

Description:
The present application is based on Japanese Patent Application No. 2013-190448 filed on Sep. 13, 2013 the contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to a lithium-ion secondary battery, and a method of producing the same, and more particularly to improvements of an all solid type lithium-ion secondary battery, and a method which permits advantageous production of the lithium-ion secondary battery. 
     2. Discussion of Related Art 
     A lithium-ion secondary battery having a high energy density is widely used as an electric power source in portable electronic devices such as notebook personal computers and cellular or mobile phones. This lithium-ion secondary battery is generally classified into two kinds, namely, a lithium-ion secondary battery using a liquid-type electrolyte (including a liquid electrolyte and a gel-type electrolyte), and a so-called all solid type lithium-ion secondary battery using a solid electrolyte. Of these two kinds of lithium-ion secondary battery, the all solid type lithium-ion secondary battery does not have a risk of liquid leakage and firing, and has a higher degree of safety, unlike the lithium-ion secondary battery using the liquid-type electrolyte. In favor of this advantage, there have been growing developments in the field of the all solid-type lithium-ion secondary battery, expecting a further increased demand for the all solid-type lithium-ion secondary battery. 
     Japanese Patent No. 3852169 (Patent Document 1) discloses an example of a lithium-ion secondary battery which is produced by forming: a positive electrode active substance layer in the form of an organic polymer coating layer containing a positive electrode active substance, on a positive electrode collector foil; a negative electrode active substance layer in the form of an organic polymer coating layer containing a negative electrode active substance, on a negative electrode collector foil; and a solid electrolyte layer in the form of an organic polymer coating layer containing a lithium salt, such that the positive and negative electrode active substance layers are superposed on the respective opposite surfaces of the solid electrolyte layer. 
     In the lithium-ion secondary battery configured as described above, the positive electrode active substance layer, the negative electrode active substance layer and the solid electrolyte layer are all constituted by the organic polymer films. Accordingly, these positive and negative electrode active substance layers and the solid electrolyte layer exhibit an adequate degree of flexibility or plasticity, and an accordingly high degree of bending or flexural strength. 
     In this lithium-ion secondary battery, however, the positive and negative electrode active substance layers and the solid electrolyte layer are coating layers, which have thicknesses not smaller than several tens of μm, so that there is a limitation in the amount of reduction of the thicknesses of the positive and negative electrode active substance layers and the solid electrolyte layer in an effort to reduce the overall size of the lithium-ion secondary battery and to improve its output density. Further, the production of the lithium-ion secondary battery requires an additional device for drying the positive and negative electrode active substance layers and the solid electrolyte layer, which are formed in a wet process, so that the cost of production is undesirably increased. In addition, an extra time is required for drying the positive and negative electrode active substance layers and the solid electrolyte layer after these layers are formed, so that the required cycle time of production of each lithium-ion secondary battery is necessarily prolonged, giving rise to a problem of low productivity of the battery. 
     Further, the lithium-ion secondary battery disclosed in the above-identified publication has the following drawbacks due to its structure wherein the positive and negative electrode active substance layers formed separately from the solid electrolyte layer are merely laminated on the respective opposite surfaces of the solid electrolyte layer. 
     Namely, the above-described lithium-ion secondary battery wherein the positive electrode active substance layer and the negative electrode active substance layer are superposed or laminated on the solid electrolyte layer inevitably has gaps between the solid electrolyte layer and the positive and negative electrode active substance layers, posing a problem that the gaps prevent smooth movement or transportation of lithium ions between the positive electrode active substance layer and the solid electrolyte layer, and between the negative electrode active substance layer and the solid electrolyte layer. The negative and positive electrode active substance layers may be formed by a thermal bonding process, integrally with the solid electrolyte layer. In this case, too, however, the gaps between the solid electrolyte layer and the positive and negative electrode active substance layers cannot be completely eliminated, that is, extremely minute gaps preventing the movement of the lithium ions still remain between the solid electrolyte layer and the positive and negative electrode active substance layers. 
     Accordingly, the prior art lithium-ion secondary battery in which the positive and negative electrode active substance layers and the solid electrolyte layer which have been formed separately from each other are laminated on each other suffers from a high degree of interface resistance between the solid electrolyte layer and the positive and negative electrode active substance layers, which is a big barrier to an improvement of performance of the battery. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Patent No. 3852169 
     SUMMARY OF THE INVENTION 
     The present invention was made in view of the background art described above. It is therefore a first object of the present invention to provide a lithium-ion secondary battery which is configured to permit effective improvement of its output density and effective reduction of its size, and sufficient improvement of its performance owing to reduction of an interface resistance between its solid electrolyte layer and its positive and negative electrode active substance layers, and which can be produced at a minimum cost and with a high degree of productivity. A second object of the invention is to provide a method which permits efficient production of a lithium-ion secondary battery having such excellent properties. 
     The first object indicated above can be achieved according to a first aspect of this invention, which provides a lithium-ion secondary battery comprising a plurality of laminar sheets each of which includes a positive electrode sheet and a negative electrode sheet which are laminated on each other, wherein the positive electrode sheet has a positive electrode in which a positive electrode active substance layer in the form of a vapor-deposited polymer film containing a positive electrode active substance is laminated integrally on each of opposite surfaces of a positive electrode collector foil in the form of a metallic foil, while a first solid electrolyte layer in the form of a vapor-deposited polymer film having lithium-ion conductivity is disposed on each of opposite sides of the positive electrode such that the first solid electrolyte layer is laminated integrally on the corresponding positive electrode active substance layer, and wherein the negative electrode sheet has a negative electrode in which a negative electrode active substance layer in the form of a vapor-deposited polymer film containing a negative electrode active substance is laminated integrally on each of opposite surfaces of a negative electrode collector foil in the form of a metallic foil, while a second solid electrolyte layer in the form of a vapor-deposited polymer film having lithium-ion conductivity is disposed on each of opposite sides of the negative electrode such that the second solid electrolyte layer is laminated integrally on the corresponding negative electrode active substance layer. 
     The first object can also be achieved according to a second aspect of this invention, which provides a lithium-ion secondary battery comprising a plurality of laminar sheets each including two electrode sheets which are laminated on each other and each of which has a bipolar electrode in which a positive electrode active substance layer in the form of a vapor-deposited polymer film containing a positive electrode active substance is laminated integrally on one of opposite surfaces of a collector foil in the form of a metallic foil, while a negative electrode active substance layer in the form of a vapor-deposited polymer film containing a negative electrode active substance is laminated integrally on the other of the opposite surfaces of the collector foil, and wherein a first solid electrolyte layer and a second solid electrolyte layer in the form of vapor-deposited polymer films each having lithium-ion conductivity are disposed on respective opposite sides of the bipolar electrode such that the first solid electrolyte layer is laminated integrally on the positive electrode active substance layer, while the second solid electrolyte layer is laminated integrally on the negative electrode active substance layer. 
     In a preferred form of the lithium-ion secondary battery of the invention, each of the vapor-deposited polymer film constituting the positive electrode active substance layer and the vapor-deposited polymer film constituting the negative electrode active substance layer has ion conductivity. 
     In another preferred form of the lithium-ion secondary battery of the invention, each of the vapor-deposited polymer film constituting the positive electrode active substance layer and the vapor-deposited polymer film constituting the negative electrode active substance layer has electron conductivity. 
     In a further preferred form of the lithium-ion secondary battery of the invention, a positive-electrode-side mixture layer is formed between the positive electrode active substance layer and the first solid electrolyte layer. The positive-electrode-side mixture layer is formed of a mixture of a first polymer used to form the vapor-deposited polymer film constituting the positive electrode active substance layer, and a second polymer used to form the first solid electrolyte layer. A content of the first polymer in the positive-electrode-side mixture layer gradually decreases in a direction from the positive electrode active substance layer toward the first solid electrolyte layer, while a content of the second polymer in the positive-electrode-side mixture layer gradually increases in the direction from the positive electrode active substance layer toward the first solid electrolyte layer. 
     In a yet further preferred form of the lithium-ion secondary battery of the invention, a negative-electrode-side mixture layer is formed between the negative electrode active substance layer and the second solid electrolyte layer. The negative-electrode-side mixture layer is formed of a mixture of a third polymer used to form the vapor-deposited polymer film constituting the negative electrode active substance layer, and a fourth polymer used to form the second solid electrolyte layer. A content of the third polymer in the negative-electrode-side mixture layer gradually decreases in a direction from the negative electrode active substance layer toward the second solid electrolyte layer, while a content of the fourth polymer in the negative-electrode-side mixture layer gradually increases in the direction from the negative electrode active substance layer toward the second solid electrolyte layer. 
     In a still further preferred form of the lithium-ion secondary battery of the invention, each of the first solid electrolyte layer and the second solid electrolyte layer is constituted by a vapor-deposited polymer film containing a lithium salt and having ion conductivity. 
     Where each of the first solid electrolyte layer and the second solid electrolyte layer is constituted by a vapor-deposited polymer film containing a lithium salt and having ion conductivity, contents of lithium ions and anions derived from the lithium salt existing within the first and second solid electrolyte layers are adjusted in the following manner. 
     Namely, the content of the lithium ions is higher in a thickness portion of the first solid electrolyte layer adjacent to the positive electrode active substance layer, than in the other thickness portion of the first solid electrolyte layer remote from the positive electrode active substance layer, and in a thickness portion of the second solid electrolyte layer adjacent to the negative electrode active substance layer, than in the other thickness portion of the second solid electrolyte layer remote from the negative electrode active substance layer, while the content of the anions is higher in the above-described other thickness portion of the first solid electrolyte layer, and in the above-described other thickness portion of the second solid electrolyte layer. 
     Further, only the thickness portion of the first solid electrolyte layer adjacent to the positive electrode active substance layer, and only the thickness portion of the second solid electrolyte layer adjacent to the negative electrode active substance layer are formed of a polymer having a functional group which includes an element of high electronegativity which attracts the lithium ions derived from the lithium salt contained in the first and second solid electrolyte layers, toward the thickness portions of the first and second solid electrolyte layers respectively adjacent to the positive and negative electrode active substance layers, for uneven distribution of the lithium ions in the first and second solid electrolyte layers. 
     The second object indicated above can be achieved according to a second aspect of this invention, which provides a method of producing a lithium-ion secondary battery, comprising the steps of (a) preparing a positive electrode collector foil in the form of a metallic foil, and laminating positive electrode active substance layers in the form of vapor-deposited polymer films each containing a positive electrode active substance, integrally on respective opposite surfaces of the positive electrode collector foil, (b) laminating first solid electrolyte layers in the form of vapor-deposited polymer films each having lithium-ion conductivity, on surfaces of the positive electrode active substance layers remote from the positive electrode collector foil, (c) preparing a negative electrode collector foil in the form of a metallic foil, and laminating negative electrode active substance layers in the form of vapor-deposited polymer films each containing a negative electrode active substance, integrally on respective opposite surfaces of the negative electrode collector foil, (d) laminating second solid electrolyte layers in the form of vapor-deposited polymer films each having lithium-ion conductivity, on surfaces of the negative electrode active substance layers remote from the negative electrode collector foil, to thereby form a positive electrode sheet in which the positive electrode active substance layers are laminated integrally on the respective opposite surfaces of the positive electrode collector foil, and the first solid electrolyte layers are laminated integrally on the surfaces of the positive electrode active substance layers remote from the positive electrode collector foil, and a negative electrode sheet in which the negative electrode active substance layers are laminated integrally on the respective opposite surfaces of the negative electrode collector foil, and the second solid electrolyte layers are laminated integrally on the surfaces of the negative electrode active substance layers remote from the negative electrode collector foil, and (e) laminating a plurality of laminar sheets on each other, each of the laminar sheets including the positive electrode sheet and the negative electrode sheet which are superposed on each other. 
     In a preferred form of the method of the invention, a plurality of segments of each of the positive electrode active substance layers are laminated integrally on each of opposite surfaces of a tape of the positive electrode collector foil such that the plurality of segments are spaced apart from each other by a predetermined spacing distance in a direction of length of the tape, to form the positive electrode sheet in which each of the opposite surfaces of the positive electrode collector foil is provided with active-substance-free portions each formed between the adjacent segments of the positive electrode active substance layer, and a plurality of segments of each of the negative electrode active substance layers are laminated integrally on each of opposite surfaces of a tape of the negative electrode collector foil such that the plurality of segments are spaced apart from each other by the predetermined spacing distance in a direction of length of the tape of the negative electrode collector foil, to form the negative electrode sheet in which each of the opposite surfaces of the negative electrode collector foil is provided with active-substance-free portions each formed between the adjacent segments of the negative electrode active substance layer, and wherein the positive electrode sheet and the negative electrode sheet are superposed on each other such that the active-substance-free portions of the positive and negative electrode sheets are aligned with each other, to form a laminar body which is cut into the plurality of laminar sheets, at positions of the tapes of the positive and negative electrode collector foils corresponding to the respective active-substance-free portions. 
     In another preferred form of the method of the invention, the positive electrode active substance layer consisting of a first vapor-deposited polymer film containing the positive electrode active substance is formed integrally on each of the opposite surfaces of the positive electrode collector foil, by introducing the positive electrode active substance into the first vapor-deposited polymer film while the first vapor-deposited polymer film is formed by a vapor-deposition polymerization process on each of the opposite surfaces of the positive electrode collector foil. 
     In a further preferred form of the method of the invention, the negative electrode active substance layer consisting of a second vapor-deposited polymer film containing the negative electrode active substance is formed integrally on each of the opposite surfaces of the negative electrode collector foil, by introducing the negative electrode active substance into the second vapor-deposited polymer film while the second vapor-deposited polymer film is formed by a vapor-deposition polymerization process on each of the opposite surfaces of the negative electrode collector foil. 
     In a still further preferred form of the method of the invention, the first solid electrolyte layer consisting of a third vapor-deposited polymer film containing an ion conductivity rendering substance is formed integrally on a surface of the positive electrode active substance layer remote from the positive electrode collector foil, by introducing the ion conductivity rendering substance including a lithium salt into the third vapor-deposited polymer film while the third vapor-deposited polymer film is formed by a vapor-deposition polymerization process on the surface of the positive electrode active substance layer remote from the positive electrode collector foil. 
     In a yet further preferred form of the method of the invention, the second solid electrolyte layer consisting of a fourth vapor-deposited polymer film containing an ion conductivity rendering substance is formed integrally on a surface of the negative electrode active substance layer remote from the negative electrode collector foil, by introducing the ion conductivity rendering substance including a lithium salt into the fourth vapor-deposited polymer film while the fourth vapor-deposited polymer film is formed by a vapor-deposition polymerization process on the surface of the negative electrode active substance layer remote from the negative electrode collector foil. 
     The second object indicated above can also be achieved according to a fourth aspect of the present invention, which provides a method of producing a lithium-ion secondary battery, comprising the steps of (a) preparing a collector foil in the form of a metallic foil, (b) forming a positive electrode active substance layer in the form of a vapor-deposited polymer film containing a positive electrode active substance, integrally on one of opposite surfaces of the collector foil, (c) forming a negative electrode active substance layer in the form of a vapor-deposited polymer film containing a negative electrode active substance, integrally on the other of the opposite surfaces of the collector foil, (d) forming a first solid electrolyte layer in the form of a vapor-deposited polymer film having lithium-ion conductivity, integrally on a surface of the positive electrode active substance layer remote from the collector foil, (e) forming a second solid electrolyte layer in the form of a vapor-deposited polymer film having lithium-ion conductivity, integrally on a surface of the negative electrode active substance layer remote from the collector foil, to thereby form an electrode sheet in which the positive electrode active substance layer and the first solid electrolyte layer are laminated integrally on the above-described one of the opposite surfaces of the collector foil, while the negative electrode active substance layer and the second solid electrolyte layer are laminated integrally on the above-described other of the opposite surfaces of the collector foil, and (f) laminating a plurality of laminar sheets on each other, each of the laminar sheets including two electrode sheets which are superposed on each other and each of which consists of the above-described electrode sheet. 
     In a preferred form of the method according to the fourth aspect of the invention, a plurality of segments of the positive electrode active substance layer are laminated integrally on the above-described one of the opposite surfaces of a tape of the collector foil such that the plurality of segments are spaced apart from each other by a predetermined spacing distance in a direction of length of the tape, while a plurality of segments of the negative electrode active substance layer are laminated integrally on the above-described other of the opposite surfaces of the tape of the collector foil such that the plurality of segments are spaced apart from each other by the predetermined spacing distance in the direction of length of the tape, to form the above-described electrode sheet in which the above-described one of the opposite surfaces of the collector foil is provided with active-substance-free portions each formed between the adjacent segments of the positive electrode active substance layer, while the above-described other of the opposite surfaces of the collector foil is provided with active-substance-free portions each formed between the adjacent segments of the negative electrode active substance layer, and wherein the above-described two electrode sheets are superposed on each other such that the active-substance-free portions between the adjacent segments of the positive electrode active substance layer, and the active-substance-free portions between the adjacent segments of the negative electrode active substance layer are aligned with each other, to form a laminar body which is cut into the plurality of laminar sheets, at positions of the tape of the collector foil corresponding to the respective active-substance-free portions. 
     In another preferred form of the method according to the fourth aspect of the invention, the positive electrode active substance layer consisting of a first vapor-deposited polymer film containing the positive electrode active substance is formed integrally on the above-described one of the opposite surfaces of the collector foil, by introducing the positive electrode active substance into the first vapor-deposited polymer film while the first vapor-deposited polymer film is formed by a vapor-deposition polymerization process on the above-described one of the opposite surfaces of the collector foil. 
     In a further preferred form of the method according to the fourth aspect of the invention, the negative electrode active substance layer consisting of a second vapor-deposited polymer film containing the negative electrode active substance is formed integrally on the above-described other of the opposite surfaces of the collector foil, by introducing the negative electrode active substance into the second vapor-deposited polymer film while the second vapor-deposited polymer film is formed by a vapor-deposition polymerization process on the above-described other of the opposite surfaces of the collector foil. 
     In a still further preferred form of the method according to the fourth aspect of the invention, the first solid electrolyte layer consisting of a third vapor-deposited polymer film containing an ion conductivity rendering substance is laminated integrally on a surface of the positive electrode active substance layer remote from the collector foil, by introducing the ion conductivity rendering substance including a lithium salt into the third vapor-deposited polymer film while the third vapor-deposited polymer film is formed by a vapor-deposition polymerization process on the surface of the positive electrode active substance layer remote from the collector foil. 
     In a yet further preferred form of the method according to the fourth aspect of the invention, the second solid electrolyte layer consisting of a fourth vapor-deposited polymer film containing an ion conductivity rendering substance is laminated integrally on a surface of the negative electrode active substance layer remote from the collector foil, by introducing the ion conductivity rendering substance including a lithium salt into the fourth vapor-deposited polymer film while the fourth vapor-deposited polymer film is formed by a vapor-deposition polymerization process on the surface of the negative electrode active substance layer remote from the collector foil. 
     In another preferred form of the method according to the fourth aspect of the invention, the positive electrode active substance is introduced into the first vapor-deposited polymer film by blowing the positive electrode active substance dispersed in a first carrier gas, onto the first vapor-deposited polymer film while the first vapor-deposited polymer film is formed. 
     In a further preferred form of the method according to the fourth aspect of the invention, the negative electrode active substance is introduced into the second vapor-deposited polymer film by blowing the negative electrode active substance dispersed in a second carrier gas, onto the second vapor-deposited polymer film while the second vapor-deposited polymer film is formed. 
     In a still further preferred form of the method according to the fourth aspect of the invention, each of the first and second vapor-deposited polymer films has ion conductivity. 
     In a yet further preferred form of the method according to the fourth aspect of the invention, each of the first and second vapor-deposited polymer films has electron conductivity. 
     Where each of the first and second solid electrolyte layers is constituted by a vapor-deposited polymer film containing a lithium salt and having ion conductivity, contents of lithium ions and anions derived from the lithium salt existing within the first and second solid electrolyte layers are adjusted in the following manner. 
     Namely, before lamination of the above-described positive and negative electrode sheets or the above-described two electrode sheets, a processing operation to unevenly distribute the lithium ions derived from the lithium salt contained in the first solid electrolyte layer is performed such that the content of the lithium ions is higher in a thickness portion of the first solid electrolyte layer adjacent to the positive electrode active substance layer, than in the other thickness portion of the first solid electrolyte layer remote from the positive electrode active substance layer, while the content of the anions is higher in the above-described other thickness portion of the first solid electrolyte layer, and a processing operation to unevenly distribute the lithium ions derived from the lithium salt contained in the second solid electrolyte layer is performed such that the content of the lithium ions is higher in a thickness portion of the second solid electrolyte layer adjacent to the negative electrode active substance layer, than in the other thickness portion of the second solid electrolyte layer remote from the negative electrode active substance layer, while the content of the anions is higher in the above-described other thickness portion of the second solid electrolyte layer. 
     Further, only the thickness portion of the third vapor-deposited polymer film of the first solid electrolyte layer adjacent to the positive electrode active substance layer, and only the thickness portion of the fourth vapor-deposited polymer film of the second solid electrolyte layer adjacent to the negative electrode active substance layer are formed of a polymer having a functional group which includes an element of high electronegativity which attracts the lithium ions derived from the lithium salt contained in the first and second solid electrolyte layers, toward the thickness portions of the first and second solid electrolyte layers respectively adjacent to the positive and negative electrode active substance layers, for uneven distribution of the lithium ions in the first and second solid electrolyte layers. 
     Further, the lithium ion conductivity rendering substance to be introduced into the third vapor-deposited polymer film of the first solid electrolyte layer consists of only the lithium salt, and the third vapor-deposited polymer film contains an ion-conductive polymer. The lithium salt is introduced into the third vapor-deposited polymer film containing the ion-conductive polymer, by blowing the lithium salt dispersed in a third carrier gas, onto the third vapor-deposited polymer film while the third vapor-deposited polymer film is formed. 
     Alternatively, the lithium ion conductivity rendering substance to be introduced into the third vapor-deposited polymer film of the first solid electrolyte layer consists of an ion-conductive polymer in a liquid state in which the lithium salt is dissolved. Particles of the ion-conductive polymer in the liquid state in which the lithium salt is dissolved are introduced into the third vapor-deposited polymer film, by blowing a mist of the particles dispersed in a fourth carrier gas, onto the third vapor-deposited polymer film while the third vapor-deposited polymer film is formed. 
     Further, the lithium ion conductivity rendering substance to be introduced into the fourth vapor-deposited polymer film of the second solid electrolyte layer consists of only the lithium salt, and the fourth vapor-deposited polymer film contains an ion-conductive polymer. The lithium salt is introduced into the fourth vapor-deposited polymer film containing the ion-conductive polymer, by blowing the lithium salt dispersed in a fifth carrier gas, onto the fourth vapor-deposited polymer film while the fourth vapor-deposited polymer film is formed. 
     Alternatively, the lithium ion conductivity rendering substance to be introduced into the fourth vapor-deposited polymer film of the second solid electrolyte layer consists of an ion-conductive polymer in a liquid state in which the lithium salt is dissolved. Particles of the ion-conductive polymer in the liquid state in which the lithium salt is dissolved are introduced into the fourth vapor-deposited polymer film, by blowing a mist of the particles dispersed in a sixth carrier gas, onto the fourth vapor-deposited polymer film while the fourth vapor-deposited polymer film is formed. 
     Further, the method of producing the lithium-ion secondary battery comprises: a step of forming the positive electrode active substance layer integrally on one of the opposite surfaces of the positive electrode collector foil by introducing the positive electrode active substance into the first vapor-deposited polymer film while the first vapor-deposited polymer film is formed on the above-described one of the opposite surfaces of the positive electrode collector foil, by introducing vapors of a plurality of kinds of material for the positive electrode active substance layer, into an evacuated reaction chamber accommodating the positive electrode collector foil, and polymerizing the vapors; and a step of forming the first solid electrolyte layer integrally on the surface of the positive electrode active substance layer remote from the positive electrode collector foil, by introducing the lithium ion conductivity rendering substance into the third vapor-deposited polymer film while the third vapor-deposited polymer film is formed on the positive electrode active substance layer by introducing vapors of a plurality of kinds of material for the first solid electrolyte layer, into the evacuated reaction chamber, and polymerizing the vapors, after a predetermined length of time has passed after a moment of initiation of the step of forming the positive electrode active substance layer, and wherein amounts of introduction of the vapors of the plurality of kinds of material for the positive electrode active substance layer into the reaction chamber are gradually reduced to zero after a moment of initiation of introduction of the vapors of the plurality of kinds of material for the first solid electrolyte layer into the reaction chamber, so that the polymerization of the vapors of the plurality of kinds of material for the positive electrode active substance layer and the polymerization of the vapors of the plurality of kinds of material for the first solid electrolyte layer take place concurrently, whereby a positive-electrode-side mixture layer consisting of a mixture of a product produced by the polymerization of the vapors of the plurality of kinds of material for the positive electrode active substance layer and a product produced by the polymerization of the vapors of the plurality of kinds of material for the first solid electrolyte layer is formed on the positive electrode active substance layer before the first solid electrolyte layer is formed. 
     The method of producing the lithium-ion secondary battery further comprises: a step of forming the negative electrode active substance layer integrally on one of the opposite surfaces of the negative electrode collector foil, by introducing the negative electrode active substance into the second vapor-deposited polymer film while the second vapor-deposited polymer film is formed on the above-described one of the opposite surfaces of the negative electrode collector foil by introducing vapors of a plurality of kinds of material for the negative electrode active substance layer, into the evacuated reaction chamber also accommodating the negative electrode collector foil, and polymerizing the vapors; and a step of forming the second solid electrolyte layer integrally on the surface of the negative electrode active substance layer remote from the negative electrode collector foil, by introducing the lithium ion conductivity rendering substance into the fourth vapor-deposited polymer film while the fourth vapor-deposited polymer film is formed on the negative electrode active substance layer by introducing vapors of a plurality of kinds of material for the second solid electrolyte layer, into the evacuated reaction chamber, and polymerizing the vapors, after a predetermined length of time has passed after a moment of initiation of the step of forming the negative electrode active substance layer, and wherein amounts of introduction of the vapors of the plurality of kinds of material for the negative electrode active substance layer into the reaction chamber are gradually reduced to zero after a moment of initiation of introduction of the vapors of the plurality of kinds of material for the second solid electrolyte layer into the reaction chamber, so that the polymerization of the vapors of the plurality of kinds of material for the negative electrode active substance layer and the polymerization of the vapors of the plurality of kinds of material for the second solid electrolyte layer take place concurrently, whereby a negative-electrode-side mixture layer consisting of a mixture of a product produced by the polymerization of the vapors of the plurality of kinds of material for the negative electrode active substance layer and a product produced by the polymerization of the vapors of the plurality of kinds of material for the second solid electrolyte layer is formed on the negative electrode active substance layer before the second solid electrolyte layer is formed. 
     Further, the method of producing the lithium-ion secondary battery comprises: a step of forming the positive electrode active substance layer integrally on one of the opposite surfaces of the collector foil, by introducing the positive electrode active substance into the first vapor-deposited polymer film while the first vapor-deposited polymer film is formed on the above-described one of the opposite surfaces of the collector foil by introducing vapors of a plurality of kinds of material for the positive electrode active substance layer, into an evacuated reaction chamber accommodating the collector foil, and polymerizing the vapors; and a step of forming the first solid electrolyte layer integrally on the surface of the positive electrode active substance layer remote from the collector foil, by introducing the lithium ion conductivity rendering substance into the third vapor-deposited polymer film while the third vapor-deposited polymer film is formed on the positive electrode active substance layer by introducing vapors of a plurality of kinds of material for the first solid electrolyte layer, into the evacuated reaction chamber, and polymerizing the vapors, after a predetermined length of time has passed after a moment of initiation of the step of forming the positive electrode active substance layer, and wherein amounts of introduction of the vapors of the plurality of kinds of material for the positive electrode active substance layer into the reaction chamber are gradually reduced to zero after a moment of initiation of introduction of the vapors of the plurality of kinds of material for the first solid electrolyte layer into the reaction chamber, so that the polymerization of the vapors of the plurality of kinds of material for the positive electrode active substance layer and the polymerization of the vapors of the plurality of kinds of material for the first solid electrolyte layer take place concurrently, whereby a positive-electrode-side mixture layer consisting of a mixture of a product produced by the polymerization of the vapors of the plurality of kinds of material for the positive electrode active substance layer and a product produced by the polymerization of the vapors of the plurality of kinds of material for the first solid electrolyte layer is formed on the positive electrode active substance layer before the first solid electrolyte layer is formed. 
     The method of producing the lithium-ion secondary battery further comprises: a step of forming the negative electrode active substance layer integrally on the other of the opposite surfaces of the collector foil, by introducing the negative electrode active substance into the second vapor-deposited polymer film while the second vapor-deposited polymer film is formed on the above-described other of the opposite surfaces of the collector foil by introducing vapors of a plurality of kinds of material for the negative electrode active substance layer, into the evacuated reaction chamber accommodating the collector foil, and polymerizing the vapors; and a step of forming the second solid electrolyte layer integrally on the surface of the negative electrode active substance layer remote from the collector foil, by introducing the lithium ion conductivity rendering substance into the fourth vapor-deposited polymer film while the fourth vapor-deposited polymer film is formed on the negative electrode active substance layer by introducing vapors of a plurality of kinds of material for the second solid electrolyte layer, into the evacuated reaction chamber, and polymerizing the vapors, after a predetermined length of time has passed after a moment of initiation of the step of forming the negative electrode active substance layer, and wherein amounts of introduction of the vapors of the plurality of kinds of material for the negative electrode active substance layer into the reaction chamber are gradually reduced to zero after a moment of initiation of introduction of the vapors of the plurality of kinds of material for the second solid electrolyte layer into the reaction chamber, so that the polymerization of the vapors of the plurality of kinds of material for the negative electrode active substance layer and the polymerization of the vapors of the plurality of kinds of material for the second solid electrolyte layer take place concurrently, whereby a negative-electrode-side mixture layer consisting of a mixture of a product produced by the polymerization of the vapors of the plurality of kinds of material for the negative electrode active substance layer and a product produced by the polymerization of the vapors of the plurality of kinds of material for the second solid electrolyte layer is formed on the negative electrode active substance layer before the second solid electrolyte layer is formed. 
     The lithium-ion secondary battery according to the present invention is preferably produced by a production apparatus comprising (a) a vacuum chamber, (b) evacuating means for exhausting air from the vacuum chamber to thereby evacuate the vacuum chamber, (c) positive electrode collector foil supplying means for continuously supplying a tape of a positive electrode collector foil in the form of a metallic foil, within the vacuum chamber, (d) negative electrode collector foil supplying means for continuously supplying a tape of a negative electrode collector foil in the form of a metallic foil, within the vacuum chamber, (e) a positive electrode sheet forming unit configured to form a positive electrode sheet by integrally laminating a positive electrode active substance layer in the form of a vapor-deposited polymer film containing a positive electrode active substance, and a first solid electrolyte layer in the form of a vapor-deposited polymer film having lithium-ion conductivity, in this order of description within the vacuum chamber, on each of opposite surfaces of the tape of the positive electrode collector foil supplied from the positive electrode collector foil supplying means, (f) a negative electrode sheet forming unit configured to form a negative electrode sheet by integrally laminating a negative electrode active substance layer in the form of a vapor-deposited polymer film containing a negative electrode active substance, and a second solid electrolyte layer in the form of a vapor-deposited polymer film having lithium-ion conductivity, in this order of description within the vacuum chamber, on each of opposite surfaces of the tape of the negative electrode collector foil supplied from the negative electrode collector foil supplying means, (g) a laminar sheet forming unit configured to superpose the positive electrode sheet formed by the positive electrode sheet forming unit, and the negative electrode sheet formed by the negative electrode sheet forming unit, on each other within the vacuum chamber, such that the first solid electrolyte layer and the second solid electrolyte layer are superposed on each other, and (h) laminating means for laminating a plurality of laminar sheets each produced by the laminar sheet forming unit, on each other. 
     In one preferred form of the production apparatus described above, the positive electrode sheet forming unit includes first vapor-deposited polymer film forming means for laminating a first vapor-deposited polymer film by a vapor-deposition polymerization process, integrally on each of the opposite surfaces of the tape of the positive electrode collector foil supplied from the positive electrode collector foil supplying means, and positive electrode active substance introducing means for introducing the positive electrode active substance into the first vapor-deposited polymer film while the first vapor-deposited polymer film is formed by the first vapor-deposited polymer film forming means, the first vapor-deposited polymer film forming means and the positive electrode active substance introducing means cooperating to form the first vapor-deposited polymer film containing the positive electrode active substance, which constitutes the positive electrode active substance layer, the positive electrode sheet forming unit further including second vapor-deposited polymer film forming means for laminating a second vapor-deposited polymer film by a vapor-deposition polymerization process, integrally on the surface of the positive electrode active substance layer remote from the positive electrode collector foil, and lithium salt introducing means for introducing a lithium-ion conductivity rendering substance including a lithium salt, into the second vapor-deposited polymer film while the second vapor-deposited polymer film is formed by the second vapor-deposited polymer film forming means, the second vapor-deposited polymer film forming means and the lithium salt introducing means cooperating to form the second vapor-deposited polymer film containing the lithium-ion conductivity rendering substance, which constitutes the first solid electrolyte layer. 
     In another preferred form of the production apparatus, the negative electrode sheet forming unit includes third vapor-deposited polymer film forming means for laminating a third vapor-deposited polymer film by a vapor-deposition polymerization process, integrally on each of the opposite surfaces of the tape of the negative electrode collector foil supplied from the negative electrode collector foil supplying means, and negative electrode active substance introducing means for introducing the negative electrode active substance into the third vapor-deposited polymer film while the third vapor-deposited polymer film is formed by the third vapor-deposited polymer film forming means, the third vapor-deposited polymer film forming means and the negative electrode active substance introducing means cooperating to form the third vapor-deposited polymer film containing the negative electrode active substance, which constitutes the negative electrode active substance layer, the negative electrode sheet forming unit further including fourth vapor-deposited polymer film forming means for laminating a fourth vapor-deposited polymer film by a vapor-deposition polymerization process, integrally on the surface of the negative electrode active substance layer remote from the negative electrode collector foil, and lithium salt introducing means for introducing a lithium-ion conductivity rendering substance including a lithium salt, into the fourth vapor-deposited polymer film while the fourth vapor-deposited polymer film is formed by the fourth vapor-deposited polymer film forming means, the fourth vapor-deposited polymer film forming means and the lithium salt introducing means cooperating to form the fourth vapor-deposited polymer film containing the lithium-ion conductivity rendering substance, which constitutes the second solid electrolyte layer. 
     The lithium-ion secondary battery according to the present invention is also preferably produced by a production apparatus comprising (a) a vacuum chamber, (b) evacuating means for exhausting air from the vacuum chamber to thereby evacuate the vacuum chamber, (c) collector foil supplying means for continuously supplying a tape of a collector foil, within the vacuum chamber, (d) an electrode sheet forming unit configured to form an electrode sheet by integrally laminating a positive electrode active substance layer in the form of a vapor-deposited polymer film containing a positive electrode active substance, and a first solid electrolyte layer in the form of a vapor-deposited polymer film having lithium-ion conductivity, in this order of description within the vacuum chamber, integrally on one of opposite surfaces of the tape of the collector foil supplied from the collector foil supplying means, and integrally laminating a negative electrode active substance layer in the form of a vapor-deposited polymer film containing a negative electrode active substance, and a second solid electrolyte layer in the form of a vapor-deposited polymer film having lithium-ion conductivity, in this order of description within the vacuum chamber, on the other of the opposite surfaces of the tape of the collector foil, (e) a laminar sheet forming unit configured to form a laminar sheet consisting of two electrode sheets each of which is formed by the electrode sheet forming unit and which are superposed on each other within the vacuum chamber, such that the first solid electrolyte layer and the second solid electrolyte layer are superposed on each other, and (f) laminating means for laminating a plurality of laminar sheets each produced by the laminar sheet forming unit, on each other. 
     In one preferred form of the production apparatus described above, the electrode sheet forming unit includes first vapor-deposited polymer film forming means for laminating a first vapor-deposited polymer film by a vapor-deposition polymerization process, integrally on one of the opposite surfaces of the tape of the collector foil supplied from the collector foil supplying means, and positive electrode active substance introducing means for introducing the positive electrode active substance into the first vapor-deposited polymer film while the first vapor-deposited polymer film is formed by the first vapor-deposited polymer film forming means, the first vapor-deposited polymer film forming means and the positive electrode active substance introducing means cooperating to form the first vapor-deposited polymer film containing the positive electrode active substance, which constitutes the positive electrode active substance layer, the electrode sheet forming unit further including second vapor-deposited polymer film forming means for laminating a second vapor-deposited polymer film by a vapor-deposition polymerization process, integrally on one of the opposite surfaces of the positive electrode active substance layer remote from the collector foil, and lithium salt introducing means for introducing a lithium-ion conductivity rendering substance including a lithium salt, into the second vapor-deposited polymer film while the second vapor-deposited polymer film is formed by the second vapor-deposited polymer film forming means, the second vapor-deposited polymer film forming means and the lithium salt introducing means cooperating to form the second vapor-deposited polymer film containing the lithium-ion conductivity rendering substance, which constitutes the first solid electrolyte layer, the electrode sheet forming unit further including third vapor-deposited polymer film forming means for laminating a third vapor-deposited polymer film by a vapor-deposition polymerization process, integrally on the other of the opposite surfaces of the tape of the collector foil, and negative electrode active substance introducing means for introducing the negative electrode active substance into the third vapor-deposited polymer film while the third vapor-deposited polymer film is formed by the third vapor-deposited polymer film forming means, the third vapor-deposited polymer film forming means and the negative electrode active substance introducing means cooperating to form the third vapor-deposited polymer film containing the negative electrode active substance, which constitutes the negative electrode active substance layer, the electrode sheet forming unit further including fourth vapor-deposited polymer film forming means for laminating a fourth vapor-deposited polymer film by a vapor-deposition polymerization process, integrally on one of the opposite surfaces of the negative electrode active substance layer remote from the collector foil, and lithium salt introducing means for introducing a lithium-ion conductivity rendering substance including a lithium salt, into the fourth vapor-deposited polymer film while the fourth vapor-deposited polymer film is formed by the fourth vapor-deposited polymer film forming means, the fourth vapor-deposited polymer film forming means and the lithium salt introducing means cooperating to form the fourth vapor-deposited polymer film containing the lithium-ion conductivity rendering substance, which constitutes the second solid electrolyte layer. 
     The lithium-ion secondary battery according to the first aspect of this invention is configured such that each of the positive electrode active substance layer, the negative electrode active substance layer, the first solid electrolyte layer and the second solid electrolyte layer is constituted by a vapor-deposited polymer film. This vapor-deposited polymer film is formed at a high rate with an extremely small thickness from about several tens of nanometers to about several tens of micrometers, by a vapor-deposition polymerization process, which is a kind of thin-film forming process in vacuum. Accordingly, the present lithium-ion secondary battery wherein each of the positive and negative electrode active substance layers and the first and second solid electrolyte layers is constituted by the vapor-deposited polymer film is free of all drawbacks experienced in a prior art lithium-ion secondary battery in which the positive and negative electrode active substance layers and the first and second solid electrolyte layers are constituted by respective coating layers. 
     The present lithium-ion secondary battery is further configured such that the first solid electrolyte layer constituted by the vapor-deposited polymer film is laminated integrally on the positive electrode active substance layer, while the second solid electrolyte layer constituted by the vapor-deposited polymer film is laminated integrally on the negative electrode active substance layer, so that gaps which would disturb movements of lithium ions do not exist between the positive electrode active substance layer and the first solid electrolyte layer, and between the negative electrode active substance layer and the second solid electrolyte layer, whereby an interface resistance between the first solid electrolyte layer and the positive electrode active substance layer, and between the second solid electrolyte layer and the negative electrode active substance layer can be effectively reduced. Thus, the present lithium-ion secondary battery advantageously has a considerably improved cell performance. 
     It is noted that the first solid electrolyte layer of the positive electrode sheet and the second solid electrolyte layer of the negative electrode sheet are superposed on each other, with the lamination of the positive and negative electrode sheets on each other, so that gaps which may disturb the movements of the lithium ions are formed between the first and second solid electrolyte layers. During charging and discharging of the lithium-ion secondary battery, however, substantially no movements of the lithium ions actually take place between the first and second solid electrolyte layers, although the lithium ions move between the positive electrode active substance layer and the first solid electrolyte layer, and between the negative electrode active substance layer and the second solid electrolyte layer. Accordingly, the gaps which may disturb the movements of the lithium ions between the first and second solid electrolyte layers do not actually have any adverse influence on the performance of the lithium-ion secondary battery. 
     Further, the lithium-ion secondary battery according to the first aspect of this invention includes the mutually laminated plurality of laminar sheets each of which includes the positive electrode sheet including the positive electrode active substance layer and the first solid electrolyte layer laminated integrally on each of the opposite surfaces of the positive electrode collector foil, and the negative electrode sheet including the negative electrode active substance layer and the second solid electrolyte layer laminated integrally on each of the opposite surfaces of the negative electrode collector foil. Therefore, neither the positive electrode collector foils of the positive electrode sheets, nor the negative electrode collector foils of the negative electrode sheets are superposed on each other, with the lamination of the laminar sheets on each other, in the present lithium-ion secondary battery, contrary to the superposition of the positive electrode collector foils on each other and the superposition of the negative electrode collector foils on each other in a lithium-ion secondary battery in which the positive electrode active substance layer and the first solid electrolyte layer are laminated integrally on only one of the opposite surfaces of the positive electrode collector foil while the negative electrode active substance layer and the second solid electrolyte layer are laminated integrally on only one of the opposite surfaces of the negative electrode collector foil. Namely, the present lithium-ion secondary battery do not have two positive electrode collector foils superposed on each other, or two negative electrode collector foils superposed on each other. Accordingly, the required amount of the positive and negative collector foils can be advantageously reduced, and the material cost of the present lithium-ion secondary battery can be effectively reduced. 
     The lithium-ion secondary battery according to the first aspect of this invention described above has an effectively improved output density and an effectively reduced size, and a sufficiently improved cell performance owing to reduction of the interface resistance between the solid electrolyte layers and the positive and negative electrode active substance layers. In addition, the present lithium-ion secondary battery can be efficiently produced at a minimum cost with a high degree of productivity. 
     The lithium-ion secondary battery according to the second aspect of the invention has substantially the same operational and physical advantages as the lithium-ion secondary battery according to the first aspect of the invention described above. 
     The methods of producing a lithium-ion secondary battery according to the third and fourth aspects of this invention described above permit efficient production of the lithium-ion secondary battery at a minimum cost and with a high degree of productivity, so as to assure an effectively improved output density, an effectively reduced size, and a sufficiently improved cell performance owing to reduction of the interface resistance between the solid electrolyte layers and the positive and negative electrode active substance layers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an enlarged fragmentary cross sectional view of a lithium-ion secondary battery having a structure according to a first embodiment of the present invention; 
         FIG. 2  is a cross sectional view of a battery cell formed by using the lithium-ion secondary battery shown in  FIG. 1 ; 
         FIG. 3  is a schematic view of one example of a production apparatus used to produce the lithium-ion secondary battery shown in  FIG. 1 ; 
         FIG. 4  is an enlarged view of a portion A indicated in  FIG. 3 ; 
         FIG. 5  is a view corresponding to that of  FIG. 1 , showing a lithium-ion secondary battery having a structure according to a second embodiment of the invention; 
         FIG. 6  is a schematic view of one example of a production apparatus used to produce the lithium-ion secondary battery shown in  FIG. 5 , according to the second embodiment of the invention; 
         FIG. 7  is a schematic view of another example of a production apparatus used to produce the lithium-ion secondary battery shown in  FIG. 5 , according to a third embodiment of the invention; 
         FIG. 8  is a view corresponding to that of  FIG. 1 , showing a lithium-ion secondary battery having a structure according to a fourth embodiment of this invention; 
         FIG. 9  is a schematic view of one example of a production apparatus used to produce the lithium-ion secondary battery shown in  FIG. 8 , according to the fourth embodiment of the invention; and 
         FIG. 10  is a view corresponding to that of  FIG. 2 , showing another example of a battery cell formed by using a lithium-ion secondary battery having a structure according to a fifth embodiment of this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     To further clarify the present invention, preferred embodiments of the invention will be described in detail by reference to the drawings. 
     Referring first to the fragmentary longitudinal cross sectional view of  FIG. 1 , there is shown a lithium-ion secondary battery  10  constructed according to a first embodiment of this invention. As shown in  FIG. 1 , the lithium-ion secondary battery  10  of the present embodiment is constituted by a plurality of laminar sheets  16  (two laminar sheets  16  in this specific embodiment) each of which consists of a positive electrode sheet  12  and a negative electrode sheet  14  that are laminated on each other. 
     Described more specifically, the positive electrode sheet  12  has a positive electrode  22  consisting of a positive electrode collector foil  18  and two positive electrode active substance layers  20  integrally laminated on the respective opposite surfaces of the positive electrode collector foil  18 . A first solid electrolyte layer  24  is integrally laminated on one of the opposite surfaces of each of the positive electrode active substance layers  20  of the positive electrode  22 , which one surface is remote from the positive electrode collector foil  18 . The negative electrode sheet  14  has a negative electrode  30  consisting of a negative electrode collector foil  26  and two negative electrode active substance layers  28  integrally laminated on the respective opposite surfaces of the negative electrode collector foil  26 . A second solid electrolyte layer  32  is integrally laminated on one of the opposite surfaces of each of the negative electrode active substance layers  28  of the negative electrode  30 , which one surface is remote from the negative electrode collector foil  26 . 
     The positive electrode collector foil  18  of the positive electrode sheet  12  and the negative electrode collector foil  26  of the negative electrode sheet  14  are metallic foils. In the present embodiment, the positive electrode collector foil  18  is an aluminum foil, while the negative electrode collector foil  26  is a copper foil. In this respect, it is noted that the positive electrode collector foil  18  and the negative electrode collector foil  26  may be formed of any materials other than aluminum and copper, such as titanium, nickel, iron and other metallic materials, and alloys of those metallic materials. 
     In the lithium-ion secondary battery  10  according to the present embodiment, one of the opposite widthwise end portions (right end portion as seen in  FIG. 2 ) of each of the positive electrode collector foils  18  extends from the corresponding one of the opposite widthwise end faces (right end face as seen in  FIG. 2 ) of the corresponding positive electrode sheet  12 , as shown in  FIG. 2 . On the other hand, one of the opposite widthwise end portions (left end portion as seen in  FIG. 2 ) of each of the negative electrode collector foils  26  extends from the corresponding one of the opposite widthwise end faces (left end face as seen in  FIG. 2 ) of the corresponding negative electrode sheet  14 , as also shown in  FIG. 2 . 
     As is apparent from  FIG. 1 , each of the positive electrode active substance layers  20  consists of a first vapor-deposited polymer film in the form of a positive-electrode vapor-deposited polymer film  36  containing a multiplicity of particles or granules of a positive electrode active substance  34 , while each of the negative electrode active substance layers  28  consists of a second vapor-deposited polymer film in the form of a negative-electrode vapor-deposited polymer film  40  containing a multiplicity of particles or granules of a negative electrode active substance  38 . 
     The positive electrode active substance  34  contained in the positive electrode active substance layer  20  (positive electrode vapor-deposited polymer film  36 ) is LiCoO 2 . However, the positive electrode active substance  34  is not limited to LiCoO 2 , but may be any active substance used in the prior art lithium-ion secondary battery. For instance, the positive electrode active substance  34  may be one or any combination of: Li(Ni—Mn—Co)O 2  (Ni of which may be partially replaced by Co or Mn); LiNiO 2 ; LiMn 2 O 4 ; LiFePO 4 ; LiMn x Fe 1-x PO 4 ; V 2 O 5 ; V 6 O 13 ; and TiS 2 . 
     The negative electrode active substance  38  contained in the negative electrode active substance layer  28  (negative electrode vapor-deposited polymer film  40 ) is natural graphite. However, the negative electrode active substance  38  is not limited to the natural graphite, but may be any active substance used in the prior art lithium-ion secondary battery. For instance, the negative electrode active substance  38  may be one or any combination of: hard carbon; carbon nano tubes; carbon nano walls; mesophase carbon micro beads; mesophase carbon fibers; lithium metals; lithium-aluminum alloys; intercalated lithium compounds in which lithium is intercalated in graphite or carbon; Li 4 Ti 5 O 12 ; Si; SiO; alloys of Si; Sn; SnO; alloys of Sn; and MnO 2 . 
     The positive electrode active substance  34  and the negative electrode active substance  38  are contained in the form of the multiple particles or granules in the positive electrode active substance layer  20  and the negative electrode active substance layer  28 . The particles or granules of those positive electrode active substance  34  and negative electrode active substance  38  contained in the positive and negative electrode active substance layers  20  and  28  are not particularly limited in their size, but the average size of the primary particles measured by a scanning electron microscope, or the average size of the secondary particles which are agglomerates of the primary particles is generally selected within a range of about 10 nm-50 μm, since the average size of the primary or secondary particles larger than 50 μm not only makes it difficult to reduce the thickness of the lithium-ion secondary battery  10 , but also gives rise to a problem of reduction of the discharge capacity when the current density is relatively high, and since the average size of the primary or secondary particles smaller than 10 nm results in an extreme increase of the surface area per unit weight of the positive and negative electrode active substances  34 ,  38 , and an increase of the required amount of use of an auxiliary electrically conducive agent, giving rise to a risk of reduction of the energy density of the lithium-ion secondary battery  10 . 
     The multiplicity of the particles or granules of the positive electrode active substance  34  are contained in the positive-electrode vapor-deposited polymer film  36  such that the particles or granules are bonded together by a resin material of the positive-electrode vapor-deposited polymer film  36 , whereby the positive electrode active substance layer  20  is formed as a thin film. Similarly, the multiplicity of the particles or granules of the negative electrode active substance  38  are contained in the negative-electrode vapor-deposited polymer film  40  such that the particles or granules are bonded together by a resin material of the negative-electrode vapor-deposited polymer film  40 , whereby the negative electrode active substance layer  28  is formed as a thin film. 
     As described above, the positive electrode active substance layer  20  and the negative electrode active substance layer  28  are respectively constituted by the positive-electrode vapor-deposited polymer film  36  and the negative-electrode vapor-deposited polymer film  40  which are formed by a vapor-deposition polymerization process which is a kind of a vacuum dry process. Accordingly, the thicknesses of the positive and negative electrode active substance layers  20 ,  28  can be controlled on the order of several tens of nanometers, and can therefore be controlled to be extremely small and uniform. Further, the amount of impurities contained in the positive and negative electrode active substance layers  20 ,  28  is sufficiently reduced. 
     In the present embodiment, each of the positive-electrode and negative-electrode vapor-deposited polymer films  36 ,  40  is formed of polyaniline, by irradiating polyurea with a ultraviolet radiation after the polyurea is formed by a known vapor-deposition polymerization process in vacuum. Thus, the vapor-deposited polymer films  36 ,  40  have a sufficiently high degree of electron conductivity and exhibit an adequate degree of flexibility or plasticity. 
     As well known in the art, polymerization to obtain polyurea does not require heat treatment of amine (including diamine, triamine and tetraamine) and isocyanate (including diisocyanate, triisocyanate and tetraisocyanate) used as material monomers, and is carried out with a polyaddition polymerization reaction which does not involve any amount of removal of water and alcohol. Accordingly, the cost of formation of the positive-electrode and negative-electrode vapor-deposited polymer films  36 ,  40  of polyaniline obtained by irradiating polyurea with the ultraviolet radiation can be reduced in the absence of a need for using a device for the heat treatment in the process of polymerization of the material monomers, and a facility for discharging water and alcohol removed as a result of the polymerization reaction, from a reaction chamber in which the polymerization reaction takes place. Further, polyurea has a high moisture resistance, and advantageously assures a high withstand voltage with higher stability. 
     The thicknesses of the positive electrode active substance layer  20  constituted by the positive-electrode vapor-deposited polymer film  36  and the negative electrode active substance layer  28  constituted by the negative electrode vapor-deposited polymer film  40  are generally selected within a range of about 1-200 μm, since the thicknesses of the positive and negative electrode active substance layers  20 ,  28  smaller than 1 μm result in insufficient amounts of the positive electrode active substance  34  in the positive electrode active substance layer  20  and the negative electrode active substance  38  in the negative electrode active substance layer  28 , leading to a possibility of reduction of the energy density, and since the thicknesses larger than 200 μm not only make it difficult to reduce the thickness and size of the lithium-ion secondary battery  10 , but also give rise to a risk of difficulty to obtain a required amount of electric current due to an increase of the internal resistance (ion transfer resistance). 
     The resin materials used to form the positive-electrode and negative-electrode vapor-deposited polymer films  36 ,  40  are not limited to polyaniline given above by way of example. Namely, the vapor-deposited polymer films  36 ,  40  may be formed of any other known resin materials which permit the vapor-deposited polymer films  36 ,  40  to be formed integrally with the respective positive and negative electrode collector foils  18 ,  26 , and which function as a binder for bonding together the particles of the positive and negative electrode active substances  34 ,  38 . For instance, the vapor-deposited polymer films  36 ,  40  may be formed of polyurea, polyamide, polyimide, polyamideimide, polyester, polyurethane, polyazomethine, acrylic, polyparaxylylene, and perylene, other than polyaniline obtained by irradiating polyurea with a ultraviolet radiation. 
     Among the resin materials indicated above, the resin materials which have electron conductivity can be suitably used to form the positive-electrode and negative-electrode vapor-deposited polymer films  36 ,  40 , since the resin materials having the electron conductivity permit a sufficient increase of the electron conductivity and an effective reduction of membrane resistance of the positive electrode active substance layer  20  and the negative electrode active substance layer  28 , resulting in an advantageous improvement of the output density of the lithium-ion secondary battery  10 . 
     In particular, the positive-electrode and negative-electrode vapor-deposited polymer films  36 ,  40  are preferably formed of so-called electron-conductive polymers which have high electron conductivity in the absence of an auxiliary electrically conductive agent, and which can be formed by the vapor-deposition polymerization process. The use of these electron-conductive polymers increases the productivity of the lithium-ion secondary battery  10 , owing to the elimination of a step of adding the auxiliary electrically conductive agent to the polymer. For example, the electron-conductive polymers include: polyurea which has a π-conjugated structure and a side chain of which is bonded to a sulfonic acid group or a carboxyl group; and polyaniline which is obtained by irradiating the polyurea with a ultraviolet radiation, which has a π-conjugated structure and a side chain of which is bonded to a sulfonic acid group or a carboxyl group. 
     The positive-electrode and negative-electrode vapor-deposited polymer films  36 ,  40  having the electron conductivity may be formed of other resin materials instead of the above-indicated electron-conductive polymers, as long as those other resin materials have the electron conductivity in the presence of the auxiliary electrically conductive agent, and can be formed into a film by the vapor-deposition polymerization process. For example, the auxiliary electrically conductive agents which can be contained in the resin materials include: electrically conductive carbon powders such as carbon black; and electrically conductive carbon fibers such as carbon nano fibers and carbon nano tubes. 
     On the other hand, each of the first solid electrolyte layer  24  formed integrally with the surface of the positive electrode active substance layer  20  remote from the positive electrode collector foil  18 , and the second solid electrolyte layer  32  formed integrally with the surface of the negative electrode active substance layer  28  remote from the negative electrode collector foil  26 , consists of a vapor-deposited polymer film having lithium ion conductivity. Namely, like the positive electrode active substance layer  20  and the negative electrode active substance layer  28 , the first solid electrolyte layer  24  and the second solid electrolyte layer  32  are formed by the vapor-deposition polymerization process which is a kind of a vacuum dry process. Accordingly, the thicknesses of the first and second solid electrolyte layers  24 ,  32  can also be controlled on the order of several tens of nanometers, and can therefore be controlled to be extremely small and uniform. Further, the amount of impurities contained in the first and second solid electrolyte layers  24 ,  32  is sufficiently reduced. 
     In the present embodiment, the first solid electrolyte layer  24  has a two-layer structure consisting of a first inner vapor-deposited polymer film  42  and a first outer vapor-deposited polymer film  44  integrally laminated on the first inner vapor-deposited polymer film  42 . The first inner vapor-deposited polymer film  42  constitutes an inner part of the first solid electrolyte layer  24  on the side of the positive electrode active substance layer  20  and is integrally laminated on the positive electrode active substance layer  20 . The first outer vapor-deposited polymer film  44  constitutes an outer part of the first solid electrolyte layer  24  remote from the positive electrode active substance layer  20 . Similarly, the second solid electrolyte layer  32  has a two-layer structure consisting of a second inner vapor-deposited polymer film  46  and a second outer vapor-deposited polymer film  48  integrally laminated on the second inner vapor-deposited polymer film  46 . The second inner vapor-deposited polymer film  46  constitutes an inner part of the second solid electrolyte layer  32  on the side of the negative electrode active substance layer  28  and is integrally laminated on the negative electrode active substance layer  28 . The second outer vapor-deposited polymer film  48  constitutes an outer part of the second solid electrolyte layer  32  remote from the negative electrode active substance layer  28 . 
     Further, the first inner and outer vapor-deposited polymer films  42 ,  44  giving the first solid electrolyte layer  24 , and the second inner and outer vapor-deposited polymer films  46 ,  48  giving the second solid electrolyte layer  32  are all formed of polyurea in the present embodiment, so that like the positive and negative electrode active substance layers  20 ,  28  constituted by the positive-electrode and negative-electrode vapor-deposited polymer films  36 ,  40  formed of polyaniline, the first and second solid electrolyte layers  24 ,  32  can be formed at a reduced cost, and has a high withstand voltage with higher stability, and exhibits an adequate degree of flexibility or plasticity. 
     Polyurea used to form the first inner and outer vapor-deposited polymer films  42 ,  44  and the second inner and outer vapor-deposited polymer films  46 ,  48  has a repeating unit structure of polyethylene oxide represented by the following Chemical Formula (1). Further, this polyethylene oxide contains a lithium salt, so that all of the above-indicated four vapor-deposited polymer films  42 ,  44 ,  46  and  48 , and the first and second solid electrolyte layers  24  and  32  exhibit a high degree of lithium ion conductivity 
     
       
         
         
             
             
         
       
     
     In the present embodiment, the first inner vapor-deposited polymer film  42  formed integrally with the positive electrode active substance layer  20 , and the second inner vapor-deposited polymer film  46  formed integrally with the negative electrode active substance layer  28  are formed of a polymer having a functional group which includes an element of high electronegativity, namely, a polymer having a negatively charged functional group. For example, the first and second inner vapor-deposited polymer films  42 ,  46  are formed of polyurea having a cyano group CN) as a side chain 
     It is noted, however, that the lithium-ion conductive resin material of the first inner and outer vapor-deposited polymer films  42 ,  44  constituting the first solid electrolyte layer  24 , and the second inner and outer vapor-deposited polymer films  46 ,  48  constituting the second solid electrolyte layer  32  is not limited to polyurea given above by way of example. The four vapor-deposited polymer films  42 ,  44 ,  46 ,  48  may be formed of any other known lithium-ion conductive resin material which permits those polymer films to be formed integrally with the positive and negative electrode active substance layers  20 ,  28  by the vapor-deposition polymerization process. 
     Described more specifically, the resin material of the four vapor-deposited polymer films  42 - 48  of the first and second solid electrolyte layers  24 ,  32  may be selected from among: polyamide having a repeating unit structure of polyethylene oxide and containing a lithium salt in polyethylene oxide; polyimide having a repeating unit structure of polyethylene oxide and containing a lithium salt in polyethylene oxide; polyamideimide having a repeating unit structure of polyethylene oxide and containing a lithium salt in polyethylene oxide; polyester having a repeating unit structure of polyethylene oxide and containing a lithium salt in polyethylene oxide; polyurethane having a repeating unit structure of polyethylene oxide and containing a lithium salt in polyethylene oxide; polyazomethine having a repeating unit structure of polyethylene oxide and containing a lithium salt in polyethylene oxide; polyurea which contains a lithium salt and a side chain of which is bonded to a sulfonic acid group; polyamide which contains a lithium salt and a side chain of which is bonded to a sulfonic acid group; polyimide which contains a lithium salt and a side chain of which is bonded to a sulfonic acid group; polyamideimide which contains a lithium salt and a side chain of which is bonded to a sulfonic acid group; polyester which contains a lithium salt and a side chain of which is bonded to a sulfonic acid group; polyurethane which contains a lithium salt and a side chain of which is bonded to a sulfonic acid group; and polyazomethine which contains a lithium salt and a side chain of which is bonded to a sulfonic acid group. 
     In summary, the first inner and outer vapor-deposited polymer films  42 ,  44  and the second inner and outer vapor-deposited polymer films  46 ,  48  which respectively constitute the first and second solid electrolyte layers  24 ,  32  may be formed of the lithium-ion conductive resin material (hereinafter referred to as “resin A”) which has a repeating unit structure of polyethylene oxide, which contains a lithium salt in polyethylene oxide, and which can be formed into a film by the vapor-deposition polymerization process, or the lithium-ion conductive resin material (hereinafter referred to as “resin B”) which contains a lithium salt, a side chain of which is bonded to a sulfonic acid group, and which can be formed into a film by the vapor-deposited polymerization process. It is noted that the repeating unit structure of polyethylene oxide of the resin A may be bonded to the molecules of the resin A, or may not be bonded to the molecules but merely mixed in the resin A. 
     All of the first inner and outer vapor-deposited polymer films  42 ,  44  and the second inner and outer vapor-deposited polymer films  46 ,  48  need not be formed of the same resin material. For example, at least one of the four vapor-deposited polymer films  42 ,  44 ,  46 ,  48  may be formed of one of the resin materials indicated above, which is different from the resin material or materials of the other vapor-deposited polymer film or films. 
     In the present embodiment, the first and second inner vapor-deposited polymer films  42 ,  46  are formed of the above-indicated resin materials which are the polymers having, as a side chain, the functional group which includes an element of high electronegativity. More specifically described, the resin materials having any one of the following functional groups as the side chain are selected, for example: cyano group (—CN); fluoro group (—F); chloro group (—Cl); bromo group (—Br); iodo group (—I); carbonyl group (═O); carboxyl group (—COOH); hydroxyl group (—OH); nitro group (—NO 2 ); and sulfonate group (—SO 3 H). 
     The lithium salt contained in the first and second solid electrolyte layers  24  and  32  is an ion dissociation compound containing lithium, and is not particularly limited. Any kind of lithium salt conventionally used to impart lithium-ion conductivity to a desired resin material may be used. For instance, LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiBF 4  and LiClO 4  may be used as the lithium salt to be contained in the solid electrolyte layers  24 ,  32 . 
     The lithium salt is partially dissociated (ionized) in the first solid electrolyte layer  24  (first inner and outer vapor-deposited polymer films  42 ,  44 ) and the second solid electrolyte layer  32  (second inner and outer vapor-deposited polymer films  46 ,  48 ) which are formed of the ion-conductive resin material (polyurea having the repeating unit structure of polyethylene oxide, in the present embodiment), so that a portion of the lithium salt contained in the solid electrolyte layers  24 ,  32  exists therein in the form of lithium ions and anions. 
     In the lithium-ion secondary battery  10  according to the present embodiment, the polymer used to form the first inner vapor-deposited polymer film  42  of the first solid electrolyte layer  24  integrally with the positive electrode active substance layer  20 , and to form the second inner vapor-deposited polymer film  46  of the second solid electrolyte layer  32  integrally with the negative electrode active substance layer  28  has the negatively charged functional group which includes an element of high electronegativity, as described above. Accordingly, the lithium ions derived from the lithium salt existing within the first and second solid electrolyte layers  24 ,  32  are attracted by the negatively charged functional group of the polymer of the first and second inner vapor-deposited polymer films  42 ,  46 , whereby the lithium ions exist more densely in the first inner vapor-deposited polymer film  42  than in the first outer vapor-deposited polymer film  44 , and in the second inner vapor-deposited polymer film  46  than in the second outer vapor-deposited polymer film  48 .  
     Namely, the lithium ions exist more densely in a thickness portion of the first solid electrolyte layer  24  adjacent to the positive electrode active substance layer  20 , than in its intermediate thickness portion and its thickness portion remote from the positive electrode active substance layer  20  (its thickness portion adjacent to the second solid electrolyte layer  32 ), and in a thickness portion of the second solid electrolyte layer  32  adjacent to the negative electrode active substance layer  28 , than in its intermediate thickness portion and its thickness portion remote from the negative electrode active substance layer  28  (its thickness portion adjacent to the first solid electrolyte layer  24 ). That is, the lithium ions are unevenly distributed within the first and second solid electrolyte layers  24 ,  32  such that the local density of the lithium ions is higher in the thickness portion (the first inner vapor-deposited polymer film  42 ) of the first solid electrolyte layer  24  adjacent to the positive electrolyte active substance layer  20 , and in the thickness portion (the second inner vapor-deposited polymer film  46 ) of the second solid electrolyte layer  32  adjacent to the negative electrode active substance layer  28 . 
     In the present lithium-ion secondary battery  10 , the content of the lithium ions is higher in the thickness portion of the first solid electrolyte layer  24  adjacent to the positive electrode active substance layer  20 , so that a larger amount of the lithium ions move per unit time at a higher velocity between the positive electrode active substance  34  in the positive electrode active substance layer  20  and the first solid electrolyte layer  24 , during charging and discharging of the lithium-ion secondary battery  10 . Similarly, the content of the lithium ions is higher in the thickness portion of the second solid electrolyte layer  32  adjacent to the negative electrode active substance layer  28 , so that a larger amount of the lithium ions move per unit time at a higher velocity between the negative electrode active substance  38  in the negative electrode active substance layer  28  and the second solid electrolyte layer  32 , during charging and discharging of the lithium-ion secondary battery  10 . As a result, the performance of the lithium-ion secondary battery  10  is significantly and effectively improved. 
     As described above, it is generally preferred that the positive-electrode vapor-deposited polymer film  36  which constitutes the positive electrode active substance layer  20 , and the negative-electrode vapor-deposited polymer film  40  which constitutes the negative electrode active substance layer  28  are formed of the resin material having a high degree of electron conductivity, in order to improve the output density of the lithium-ion secondary battery  10 . In this respect, the performance of the present lithium-ion secondary battery  10  is improved owing to the higher content of the lithium ions in the thickness portion of the first solid electrolyte layer  24  adjacent to the positive electrode active substance layer  20  and in the thickness portion of the second solid electrolyte layer  32  adjacent to the negative electrode active substance layer  28 . 
     Therefore, a sufficient improvement of the output density can be expected even where the positive-electrode and negative-electrode vapor-deposited polymer films  36 ,  40  are formed of the ion-conductive resin material rather than the electron-conductive resin material. Where the vapor-deposited polymer films  36 ,  40  are formed of the ion-conductive resin material, there is an advantage that the lithium ions move more smoothly and more rapidly between the active substance  34  in the positive electrode active substance layer  20  and the first solid electrolyte layer  24 , and between the active substance  38  in the negative electrode active substance layer  28  and the second solid electrolyte layer  32 . 
     Where the positive-electrode and negative-electrode vapor-deposited polymer films  36 ,  40  are formed of the ion-conductive resin material, this ion-conductive resin material is preferably selected from the above-indicated ion-conductive resin materials which are used to form the first solid electrolyte layer  24  (first inner and outer vapor-deposited polymer films  42 ,  44 ) and the second solid electrolyte layer  32  (second inner and outer vapor-deposited polymer films  46 ,  48 ), and which may or may not contain a lithium salt. 
     Although the thickness of each of the first solid electrolyte layer  24  and the second solid electrolyte layer  32  is not particularly limited, it is generally selected within a range of about 25 nm-50 μm, since the thickness smaller than 25 nm makes it difficult to ensure sufficient electric insulation between the positive and negative electrode active substance layers  20 ,  28 , giving rise to a possibility of internal short-circuiting, and since the thickness larger than 50 μm not only makes it difficult to reduce the thickness of the lithium-ion secondary battery  10 , but also gives rise to a risk of reduction of the output density due to a high internal resistance. 
     The thicknesses of the first inner and outer vapor-deposited polymer films  42 ,  44  of the first solid electrolyte layer  24 , and the thicknesses of the second inner and outer vapor-deposited polymer films  46 ,  48  of the second solid electrolyte layer  32  are suitably selected depending upon the thicknesses of the first and second solid electrolyte layers  24 ,  32 . 
     In the lithium-ion secondary battery  10  according to the present embodiment, the two laminar sheets  16  each consisting of the positive and negative electrode sheets  12  and  14  constructed as described above are laminated on each other without being bonded together, such that the positive and negative electrode sheets  12 ,  14  are laminated on each other without being bonded together. 
     The lithium-ion secondary battery  10  having the structure described above has three cell elements each in the form of a laminar body consisting of the positive electrode  22 , the negative electrode  30 , and the first and second solid electrolyte layers  24  and  32 , which are integrally laminated on each other such that the positive and negative electrodes  22  and  30  are located adjacent to the respective first and second solid electrolyte layers  24 ,  32 , and such that the two positive electrode active substance layers  20  of the positive electrode  22  are integrally laminated on the respective opposite surfaces of the positive electrode collector foil  18  while the two negative electrode active substance layers  28  of the negative electrode  30  are integrally laminated on the respective opposite surfaces of the negative electrode collector foil  26 . The first solid electrolyte layer  24  and the second solid electrolyte layer  32  located between the positive electrode  22  and the negative electrode  30  are merely superposed on each other without being bonded together, with a lamination boundary being formed therebetween. In this respect, it is noted that the first and second solid electrolyte layers  24  and  32  between the positive and negative electrodes  22 ,  30  may be bonded together by a thermal bonding process. 
     For instance, the lithium-ion secondary battery  10  having the structure described above is used as a battery cell device  54  covered by two covering films  52 , as shown in  FIG. 2 . 
     Namely, the battery cell device  54  is provided with two protective films  56  laminated on the respective opposite end faces of the lithium-ion battery cell  10  which are opposed to each other in the direction of lamination of the two laminar sheets  16 . Further, the end portion of each of the two positive electrode collector foils  18  which extends from one of the widthwise opposite end faces of the corresponding laminar sheet  16  in the direction of width (right and left direction as seen in  FIG. 2 ) of the lithium-ion secondary battery  10  is welded or otherwise bonded and connected to one end portion of a positive terminal  58  which extends from the lithium-ion secondary battery  10  in its direction of width. On the other hand, the end portion of each of the two negative electrode collector foils  26  which extends from the other of the widthwise opposite end faces of the corresponding laminar sheet  16  in the direction of width of the lithium-ion secondary battery  10  is welded or otherwise bonded and connected to one end portion of a negative terminal  60  which extends from the lithium-ion secondary battery  10  in its direction of width. Thus, the three cell elements of the lithium-ion secondary battery  10  are connected in parallel with each other. 
     A laminar body consisting of the lithium-ion secondary battery  10  and the two protective films  56  is covered by the two covering films  52  such that the laminar body is sandwiched by and between the two covering films  52 . In this state, the end portion of the positive terminal  58  remote from the positive electrode collector foils  18 , and the end portion of the negative terminal  60  remote from the negative electrode collector foils  26  extend outwardly from the mutually connected end portions of the two covering films  52 . Thus, the battery cell device  54  wherein the lithium-ion secondary battery  10  is covered by the covering films  52  is formed. In  FIG. 2 , the battery cell device  54  is shown for easier understanding of its internal structure such that a space exists between the covering films  52  and the lithium-ion secondary battery  10 . However, it is to be understood that the lithium-ion secondary battery  10  and the covering films  52  are actually held in close contact with each other, without such a space existing within the battery cell device  54 . 
     The battery cell device  54  having the structure described above is used alone, or a plurality of the battery cell devices  54  are connected in parallel or in series with each other so as to constitute a battery pack. 
     For example, the lithium-ion secondary battery  10  having the structure described above is produced by a production apparatus  62  constructed as shown in  FIG. 3  according to the present embodiment. 
     As is apparent from  FIG. 3 , the production apparatus  62  has a vacuum chamber  64  as a reaction chamber. An interior space of this vacuum chamber  64  is evacuated by an operation of a vacuum pump  68  connected to an exhaust pipe  66  communicating with the interior space. It will be understood that the exhaust pipe  66  and the vacuum pump  68  constitute evacuating means in the present embodiment. 
     The production apparatus  62  further has a first supply roller  70 , a second supply roller  72 , a positive electrode sheet forming unit  74 , a negative electrode sheet forming unit  76  and a laminar sheet forming unit  78 . In  FIG. 3 , reference numeral  79  denotes tension rollers. 
     Described more specifically, each of the first supply roller  70  and the second supply roller  72  is disposed within the vacuum chamber  64  such that the supply rollers  70 ,  72  are automatically rotatable by an electric motor (not shown), for example. The first supply roller  70  is configured to receive a roll of an aluminum foil tape or strip  80  which provides the positive electrode collector foil  18 , so that the aluminum foil tape  80  is continuously fed from the roll to the positive electrode sheet forming unit  74 . Similarly, the second supply roller  72  is configured to receive a roll of a copper foil tape or strip  82  which provides the negative electrode collector foil  26 , so that the cooper foil tape  82  is continuously fed from the roll to the negative electrode sheet forming unit  76 . It will be understood from the foregoing description that the first supply roller  70  serves as positive electrode collector foil supplying means while the second supply roller  72  serves as negative electrode collector foil supplying means. 
     The positive electrode sheet forming unit  74  is configured to continuously form the positive electrode sheet  12 , and has a first feeding roller  84  and a second feeding roller  86  which are disposed within the vacuum chamber  64 . The positive electrode sheet forming unit  74  further has a positive electrode active substance layer forming unit  88 , a first inner vapor-deposited polymer film forming unit  90  and a first outer vapor-deposited polymer film forming unit  92  which correspond to the first feeding roller  84  and which are disposed outside the vacuum chamber  64 . The positive electrode sheet forming unit  74  further has another positive electrode active substance layer forming unit  88 , another first inner vapor-deposited polymer film forming unit  90  and another first outer vapor-deposited polymer film forming unit  92  which correspond to the second feeding roller  86  and which are also disposed outside the vacuum chamber  64 . 
     Each of the first feeding roller  84  and the second feeding roller  86  provided in the positive electrode sheet forming unit  74  is automatically rotatable by an electric motor (not shown), for example. The first feeding roller  84  receives the aluminum foil tape  80  fed from the first supply roller  70  being rotated, and is rotated to further feed the aluminum foil tape  80  in one of its opposite circumferential directions (namely, in a clockwise direction indicated by an arrow in  FIG. 3 ). Similarly, the second feeding roller  86  receives the aluminum foil tape  80  fed from the first feeding roller  84  being rotated, and is rotated to further feed the aluminum foil tape  80  in one of its opposite circumferential directions (namely, in a counterclockwise direction indicated by an arrow in  FIG. 3 ). In this respect, it is noted that the aluminum foil tape  80  is fed such that one of its opposite surfaces is in rolling contact with the outer circumferential surface of the first feeding roller  84 , while the other of the opposite surfaces is in rolling contact with the outer circumferential surface of the second feeding roller  86 . 
     Each of the two positive electrode active substance layer forming units  88  includes first vapor-deposited polymer film forming means in the form of a positive electrode vapor-deposited polymer film forming device  104 , positive electrode active substance introducing means in the form of a positive electrode active substance introducing device  106 , and a ultraviolet irradiating device  108 . 
     The two positive electrode active substance layer forming units  88 ,  88  are identical in construction with each other, and the two first inner vapor-deposited polymer film forming units  90 ,  90  are identical in construction with each other. Similarly, the two first outer vapor-deposited polymer film forming units  92 ,  92  are identical in construction with each other. Therefore, only the arrangements of the positive electrode active substance layer forming unit  88 , first inner vapor-deposited polymer film forming unit  90  and first outer vapor-deposited polymer film forming unit  92  which correspond to the first feeding roller  84  will be described, and the arrangement of those units  88 ,  90  and  92  corresponding to the second feeding roller  86  will not be described redundantly. 
     The positive electrode vapor-deposited polymer film forming device  104  is configured to form the positive-electrode vapor-deposited polymer film  36  by the vacuum vapor-deposition polymerization process, and has a first vapor source  110  and a second vapor source  112 . These first and second vapor sources  110  and  112  have respective monomer reservoirs, and respective heaters. The monomer reservoirs of the first and second vapor sources  110  and  112  accommodate respective two different kinds of material monomer for forming the positive-electrode vapor-deposited polymer film  36 . In the present embodiment wherein the positive-electrode vapor-deposited polymer film  36  is formed of polyaniline, the monomer reservoir of the first vapor source  110  accommodates aromatic diamine such as 1,4-phenylenediamine-2-sulfonic acid, in a liquid state, while the monomer reservoir of the second vapor source  112  accommodates aromatic diisocyanate such as 1,4-phenylene diisocyanate, in a liquid state. Those aromatic diamine and aromatic diisocyanate are monomers for obtaining polyurea before irradiation with an ultraviolet radiation. The two kinds of material monomer accommodated in the respective monomer reservoirs of the first and second vapor sources  110  and  112  are heated and evaporated by the respective heaters indicated above. 
     A vapor supply pipe  114  is provided to connect the first and second vapor sources  110  and  112  to the vacuum chamber  64 . This vapor supply pipe  114  is open toward the outer circumferential surface of the first feeding roller  84  at its end within the vacuum chamber  64 , and is open at the other end to the monomer reservoirs through respective shut-off valves, which are opened and closed to permit and inhibit flows of vapors of the material monomers into the vapor supply pipe  114 . 
     Thus, the positive electrode vapor-deposited polymer film forming device  104  is configured such that the vapors of the two kinds of material monomer generated in the first and second vapor sources  110  and  112  are introduced into the vacuum chamber  64  through the vapor supply pipe  114 , and are blown onto the aluminum foil tape  80  being fed in rolling contact with the outer circumferential surface of the first feeding roller  84 . 
     The positive electrode active substance introducing device  106  has a gas cylinder  116  charged with a carrier gas (a first carrier gas) such as an argon gas, a nitrogen gas or any other inert gas, and a powder reservoir  118  accommodating the positive electrode active substance  34  (LiCoO 2  in this embodiment) in a powdered form. A gas supply pipe  120  is provided to connect the gas cylinder  116  to the powder reservoir  118 , while a powder supply pipe  122  is provided to connect the powder reservoir  118  to the vacuum chamber  64 . The powder supply pipe  122  is partially inserted within the vapor supply pipe  114  of the above-described positive electrode vapor-deposited polymer film forming device  104 , such that the outlet end portion of the powder supply pipe  122  located within the vapor supply pipe  114  is open toward the outer circumferential surface of the first feeding roller  84 , through the corresponding outlet end portion of the vapor supply pipe  114 . Namely, the corresponding outlet end portions of the vapor supply pipe  114  and the powder supply pipe  122  on the side of the vacuum chamber  64  cooperate with each other to form a double-pipe structure. 
     In the thus constructed positive electrode active substance introducing device  106 , the carrier gas supplied from the gas cylinder  116  is introduced into the powder reservoir  118  through the gas supply pipe  120 , so that the positive electrode active substance  34  accommodated within the powder reservoir  118  is dispersed by the carrier gas introduced into the powder reservoir  118 , whereby the dispersed active substance  34  is introduced into the vacuum chamber  64 , together with the carrier gas, through the powder supply pipe  122  partially inserted within the vapor supply pipe  114 . Since the powder supply pipe  122  is partially inserted within the vapor supply pipe  114 , the positive electrode active substance  34  is mixed with the vapors of the two kinds of material monomer, within the outlet end portion of the vapor supply pipe  114 , and a mixture of the vapors of the two kinds of material monomer, positive electrode active substance  34  and carrier gas is blown from the outlet open end of the vapor supply pipe  114  onto one of the opposite surfaces of the aluminum foil tape  80  being moved in rolling contact with the outer circumferential surface of the first feeding roller  84 , such that the mixture is blown at a predetermined circumferential position of the first feeding roller  84 . 
     The gas supply pipe  120  is provided with a known mass flow controller  124  which controls a flow rate of the carrier gas, for regulating a rate of introduction of the positive electrode active substance  34  into the vacuum chamber  64 . The powder supply pipe  122  is provided with a known powder milling device  126  having a known construction, which is configured to mill or pulverize the positive electrode active substance  34  flowing through the powder supply pipe  122  together with the carrier gas, for reducing the particle size of the positive electrode active substance  34 , before the active substance  34  is blown onto the above-indicated surface of the aluminum foil tape  80 . 
     The corresponding outlet end portions of the vapor supply pipe  114  and the powder supply pipe  122  cooperating to form the double-pipe structure are provided with a shut-off valve  123  configured to concurrently open or close the vapor supply pipe  114  and the powder supply pipe  122 . For example, this shut-off valve  123  is an electromagnetic valve which is alternately opened and closed at a predetermined time interval under the control of a controller not shown, so that the mixture of the two kinds of material monomer and the positive electrode active substance  34  is intermittently blown onto the above-indicated surface of the aluminum foil tape  80  being fed in rolling contact with the outer circumferential surface of the first feeding roller  84 , while the shut-off valve  123  is alternately opened and closed. 
     The ultraviolet irradiating device  108  is disposed within the vacuum chamber  64 , at a position downstream of the outlet open end of the vapor supply pipe  114  in the direction of feeding of the aluminum foil tape  80  in rolling contact with the outer circumferential surface of the first feeding roller  84 . The ultraviolet irradiating device  108  is configured to irradiate the above-indicated surface of the aluminum foil tape  80  with an ultraviolet radiation, more specifically, irradiate, with the ultraviolet radiation, the positive-electrode vapor-deposited polymer film  36  of polyurea which is formed on the surface of the aluminum foil tape  80  by the positive electrode active substance layer forming unit  88  as described below. 
     The first inner vapor-deposited polymer film forming unit  90  includes second vapor-deposited polymer film forming means in the form of a first inner vapor-deposited polymer film forming device  128 , and lithium salt introducing means in the form of a lithium salt introducing device  130 . The first inner vapor-deposited polymer film forming device  128  is configured to form the first inner vapor-deposited polymer film  42  by the vacuum vapor-deposition polymerization process, and has a first vapor source  132 , a second vapor source  134  and a third vapor source  136 . These first, second and third vapor sources  132 ,  134  and  136  have respective monomer reservoirs, and respective heaters. The monomer reservoirs of the first, second and third vapor sources  132 ,  134  and  136  accommodate respective three different kinds of material monomer for forming the first inner vapor-deposited polymer film  42 . The three kinds of material monomer accommodated in the respective monomer reservoirs of the first, second and third vapor sources  132 ,  134  and  136  are heated and evaporated by the respective heaters. 
     In the present embodiment wherein the first inner vapor-deposited polymer film  42  is formed of polyurea which has a repeating unit structure of polyethylene oxide and a functional group (cyano group) including an element of high electronegativity, the monomer reservoirs of the first and second vapor sources  132  and  134  respectively accommodate ethylene glycol diamine such as diethylene glycol bis(3-aminopropyl)ether, and aromatic diisocyanate having a cyano group such as 1-cyano-3,5-xylylene diisocyanate, in a liquid phase, while the monomer reservoir of the third vapor source  136  accommodates oligo-ethylene oxide (low molecular polyethylene oxide having a molecular weight of 200-2000) in a liquid or solid phase. The three kinds of material monomer accommodated in the respective monomer reservoirs of the first, second and third vapor sources  132 ,  134  and  136  are heated and evaporated by the respective heaters indicated above. 
     The two kinds of material monomer used to form the polyurea which has a repeating unit structure of polyethylene oxide and a functional group including an element of high electronegativity may be a combination of the above-indicated material monomers, a combination of diethylene glycol bis(3-aminopropyl)ether and 1-fluoro-3,5-xylylene diisocyanate, or a combination of 5-bromobiphenyl-2,4′-diamine and [oxobis(trimethylene)dioxobis(trimethylene)]diisocyanate, for example. 
     A vapor supply pipe  138  is provided to connect the monomer reservoirs of the first, second and third vapor sources  132 ,  134 ,  136  to the vacuum chamber  64 . This vapor supply pipe  138  is open at its outlet end within the vacuum chamber  64 , toward the outer circumferential surface of the first feeding roller  84 , at a position downstream of the outlet open end of the vapor supply pipe  114  of the positive electrode active substance layer forming unit  88  in the direction of feeding of the aluminum foil tape  80  in rolling contact with the outer circumferential surface of the first feeding roller  84 , and open at its fixed end to the monomer reservoirs through respective shut-off valves, which are opened and closed to permit and inhibit flows of vapors of the material monomers into the vapor supply pipe  138 . 
     In the first inner vapor-deposited polymer film forming device  128 , the vapors of the three kinds of material monomer generated in the respective monomer reservoirs of the first, second and third vapor sources  132 ,  134  and  136  are introduced into the vacuum chamber  64  through the vapor supply pipe  138  and blown onto the aluminum foil tape  80  being moved in rolling contact with the outer circumferential surface of the first feeding roller  84 . 
     The lithium salt introducing device  130  has a gas cylinder  140 , a powder reservoir  142 , a gas supply pipe  144 , a mass flow controller  146 , a powder supply pipe  148 , and a powder milling device  150 . Thus, the lithium salt introducing device  130  is basically identical in construction with the positive electrode active substance introducing device  106  of the positive electrode active substance layer forming unit  88 . The gas cylinder  140  of the lithium salt introducing device  130  is charged with a carrier gas (a second carrier gas) such as an inert gas, while the powder reservoir  142  accommodates a lithium-ion conductivity rendering substance  152  in a powdered form, which is LiN(SO 2 CF 3 ) 2  in this embodiment. The powder supply pipe  148  of the lithium salt introducing device  130  is partially inserted within the outlet end portion of the vapor supply pipe  138  of the first inner vapor-deposited polymer film forming device  128 , such that the outlet end portion of the powder supply pipe  148  located within the outlet end portion of the vapor supply pipe  138  is open toward the outer circumferential surface of the first feeding roller  84 , through the corresponding outlet end portion of the vapor supply pipe  138 . 
     In the thus constructed lithium salt introducing device  130 , the carrier gas supplied from the gas cylinder  140  is introduced into the powder reservoir  142  through the gas supply pipe  144 , so that the lithium-ion conductivity rendering substance  152  accommodated within the powder reservoir  142  is dispersed in the carrier gas introduced into the powder reservoir  142 , whereby the dispersed lithium-ion conductivity rendering substance  152  is supplied to the outlet end portion of the vapor supply pipe  138 , together with the carrier gas, through the powder supply pipe  148 . The lithium-ion conductivity rendering substance  152  is mixed with the vapors of the three kinds of material monomer within the outlet end portion of the vapor supply pipe  138 , and a mixture of the vapors of the three kinds of material monomer, lithium-ion conductivity rendering substance  152  and carrier gas is blown from the outlet open end of the vapor supply pipe  138  onto one of the opposite surfaces of the aluminum foil tape  80  being moved in rolling contact with the outer circumferential surface of the first feeding roller  84 . 
     The first outer vapor-deposited polymer film forming unit  92  includes second vapor-deposited polymer film forming means in the form of a first outer vapor-deposited polymer film forming device  154 , and lithium salt introducing means in the form of a lithium salt introducing device  156 . The first outer vapor-deposited polymer film forming device  154  is configured to form the first outer vapor-deposited polymer film  44  by the vacuum vapor-deposition polymerization process. The lithium salt introducing device  156  is configured to introduce the lithium-ion conductivity rendering substance  152  into the first outer vapor-deposited polymer film  44  formed by the first outer vapor-deposited polymer film forming device  154 . The first outer vapor-deposited polymer film forming device  154  is identical in construction with the first inner vapor-deposited polymer film forming device  128  of the first inner vapor-deposited polymer film forming unit  90 , and the lithium salt introducing device  156  is identical in construction with the lithium salt introducing device  130  of the first inner vapor-deposited polymer film forming unit  90 . 
     In  FIG. 3 , the reference signs used to denote the members and portions of the first inner vapor-deposited polymer film forming device  128  and lithium salt introducing device  130  of the first inner vapor-deposited polymer film forming unit  90  are used to denote the corresponding members and portions of the first outer vapor-deposited polymer film forming device  154  and lithium salt introducing device  156  of the first outer vapor-deposited polymer film forming unit  92 , which will not be described redundantly. 
     The monomer reservoirs of the first, second and third vapor sources  132 ,  134  and  136  of the first outer vapor-deposited polymer film forming device  154  accommodate the respective three kinds of material monomer for the first outer vapor-deposited polymer film  44 , which polymer film  44  is remote from the positive electrode active substance layer  20 . In the present embodiment wherein the first outer vapor-deposited polymer film  44  is formed of polyurea which has a repeating unit structure of polyethylene oxide, the monomer reservoirs of the first and second vapor sources  132  and  134  respectively accommodate, as the respective two kinds of material monomer, ethylene glycol diamine such as diethylene glycol bis(3-aminopropyl)ether, and aromatic diisocyanate such as m-xylylene diisocyanate, in a liquid phase, while the monomer reservoir of the third vapor source  136  accommodates oligo-ethylene oxide (low molecular polyethylene oxide having a molecular weight of 200-2000) in a liquid or solid phase. The powder reservoir  142  of the lithium salt introducing device  156  accommodates the lithium-ion conductivity rendering substance  152  in a powdered form, which is LiN(SO 2 CF 3 ) 2  in this embodiment. 
     On the other hand, the negative electrode sheet forming unit  76  is configured to continuously form the negative electrode sheet  14 , and is identical in construction with the positive electrode sheet forming unit  74 , and has a first feeding roller  94  and a second feeding roller  96  which are disposed within the vacuum chamber  64 . The negative electrode sheet forming unit  76  further has a negative electrode active substance layer forming unit  98 , a second inner vapor-deposited polymer film forming unit  100  and a second outer vapor-deposited polymer film forming unit  102  which correspond to the first feeding roller  94  and which are disposed outside the vacuum chamber  64 . The negative electrode sheet forming unit  76  further has another negative electrode active substance layer forming unit  98 , another second inner vapor-deposited polymer film forming unit  100  and another second outer vapor-deposited polymer film forming unit  102  which correspond to the second feeding roller  96  and which are also disposed outside the vacuum chamber  64 . 
     The first feeding roller  94  and the second feeding roller  96  provided in the negative electrode sheet forming unit  76  are rotated to feed the copper foil tape  82  fed from the roll installed on the second supply roller  72 , in the direction indicated by arrows in  FIG. 3 , such that the opposite surfaces of the copper foil tape  82  are held in rolling contact with the outer circumferential surfaces of the respective first and second feeding rollers  94  and  96 . The first and second feeding rollers  94  and  96  are basically identical in construction with the first and second feeding rollers  84  and  86  in the positive electrode sheet forming unit  74 . 
     Each of the two negative electrode active substance layer forming units  98  includes third vapor-deposited polymer film forming means in the form of a negative electrode vapor-deposited polymer film forming device  158 , negative electrode active substance introducing means in the form of a negative electrode active substance introducing device  160 , and a ultraviolet irradiating device  161 . The negative electrode vapor-deposited polymer film forming device  158  is configured to form the negative-electrode vapor-deposited polymer film  40  by the vacuum vapor-deposition polymerization process. The negative electrode active substance introducing device  160  is configured to introduce the negative electrode active substance  38  into the negative-electrode vapor-deposited polymer film  40  formed by the negative electrode vapor-deposited polymer film forming device  158 , while the ultraviolet irradiating device  161  is configured to irradiate the negative-electrode vapor-deposited polymer film  40  containing the negative electrode active substance  38 , with an ultraviolet radiation. Those negative-electrode vapor-deposited polymer film forming device  158 , negative electrode active substance introducing device  160  and ultraviolet irradiating device  161  are identical in construction with the positive-electrode vapor-deposited polymer film forming device  104 , positive electrode active substance introducing device  106  and ultraviolet irradiating device  108  of the positive electrode active substance layer forming unit  88  of the positive electrode sheet forming unit  74 . 
     Each of the two second inner vapor-deposited polymer film forming units  100  includes fourth vapor-deposited polymer film forming means in the form of a second inner vapor-deposited polymer film forming device  162 , and lithium salt introducing means in the form of a lithium salt introducing device  164 . The second inner vapor-deposited polymer film forming device  162  is configured to form the second inner vapor-deposited polymer film  46  by the vacuum vapor-deposition polymerization process, and the lithium salt introducing device  164  is configured to introduce the lithium-ion conductivity rendering substance  152  into the second inner vapor-deposited polymer film  46  formed by the second inner vapor-deposited polymer film forming device  162 . Those second inner vapor-deposited polymer film forming device  162  and lithium salt introducing device  164  are identical in construction with the first inner vapor-deposited polymer film forming device  128  and lithium salt introducing device  130  of the first inner vapor-deposited polymer film forming unit  90  of the positive electrode sheet forming unit  74 . 
     Each of the second outer vapor-deposited polymer film forming units  102  includes fourth vapor-deposited polymer film forming means in the form of a second outer vapor-deposited polymer film forming device  166 , and lithium salt introducing means in the form of a lithium salt introducing device  168 . The second outer vapor-deposited polymer film forming device  166  is configured to form the second outer vapor-deposited polymer film  48  by the vacuum vapor-deposition polymerization process. The lithium salt introducing device  168  is configured to introduce the lithium-ion conductivity rendering substance  152  into the second outer vapor-deposited polymer film  48  formed by the second outer vapor-deposited polymer film forming device  166 . These second outer vapor-deposited polymer film forming device  166  and lithium salt introducing device  168  are identical in construction with the first outer vapor-deposited polymer film forming device  154  and lithium salt introducing device  156  of the first outer vapor-deposited polymer film forming unit  92  of the positive electrode sheet forming unit  74 . 
     In  FIG. 3 , the reference signs used to denote the members and portions of the positive electrode sheet forming unit  74  are used to denote the corresponding members and portions of the negative electrode sheet forming unit  76 , which will not be described redundantly. 
     The laminar sheet forming unit  78  has a pair of laminating rollers  170 , and a take-up roller  172 . The two laminating rollers  170  are held in rolling contact with each other at their outer circumferential surfaces, such that the laminating rollers  170  are rotatable in the respective opposite directions, by an electric motor not shown, for instance. 
     The desired lithium-ion secondary battery  10  is produced by using the thus constructed production apparatus  62 , in the following manner. 
     Initially, the leading portion of the aluminum foil tape  80  extending from the roll installed on the first supply roller  70  is partially wound on the first and second feeding rollers  84  and  86  of the positive electrode sheet forming unit  74 , in this order of description, such that the opposite surfaces of the aluminum foil tape  80  are held in contact with the outer circumferential surfaces of the respective first and second feeding rollers  84  and  86 . 
     Similarly, the leading portion of the copper foil tape  82  extending from the roll installed on the second supply roller  72  is partially wound on the first and second feeding rollers  94  and  96  of the negative electrode sheet forming unit  76 , in this order of description, such that the opposite surfaces of the copper foil tape  80  are held in contact with the outer circumferential surfaces of the respective first and second feeding rollers  94  and  96 . 
     Then, the leading end portions of the aluminum foil tape  80  and the copper foil tape  82  partially wound on the two second feeding rollers  86  and  96  are passed through the nip between the two laminating rollers  170  of the laminar sheet forming unit  78  such that these leading end portions are superposed on each other. Subsequently, the aluminum and copper foil tapes  80  and  82  are fixed at their leading end portions to the take up roller  172  so that the mutually superposed aluminum and copper foil tapes  80  and  82  are wound on the take-up roller  172 . These steps are implemented as a preparatory operation for production of the lithium-ion secondary battery  10 . 
     After the preparatory operation, the vacuum pump  68  is operated to evacuate the vacuum chamber  64  to a pressure of about 10 −4 -100 Pa. 
     Subsequently, the first feeding rollers  84  and  94  and the second feeding rollers  86  and  96  of the positive and negative electrode sheet forming units  74  and  76 , and the take-up roller  172  are rotated to continuously and concurrently feed the respective aluminum and copper foil tapes  80  and  82  from the rolls on the respective first and second supply rollers  70  and  72  toward the take-up roller  172  such that the aluminum and copper foil tapes  80  and  82  are held in rolling contact with the outer circumferential surfaces of the first feeding rollers  84  and  94  and the second feeding rollers  86  and  96  being rotated, while the aluminum and copper foil tapes  80  and  82  are superposed on each other, so that the foil tapes  80  and  82  are continuously taken up by the take-up roller  172 . 
     During continuous feeding of the aluminum and copper foil tapes  80  and  82  in the manner described above, the positive electrode sheet forming unit  74  and the negative electrode sheet forming unit  76  are operated to concurrently form the respective positive and negative electrode sheets  12  and  14 . As described above, the positive and negative electrode sheets  12  and  14  are formed in substantially the same process. The following description refers to the method of producing the positive electrode sheet  12 , by way of example, and detailed description of the method of forming the negative electrode sheet  14  will be omitted. 
     Namely, during feeding of the aluminum foil tape  80  by the first feeding roller  84 , the mixture of the vapors of the two kinds of material monomer generated in the first and second vapor sources  110  and  112  of the positive electrode vapor-deposited polymer film forming device  104  of the positive electrode active substance layer forming unit  88 , and the positive electrode active substance  34  fed from the positive electrode active substance introducing device  106  into the vapor supply pipe  114  together with the carrier gas, is blown from the outlet open end of the vapor supply pipe  114  and deposited onto the aluminum foil tape  80  being fed in rolling contact with the first feeding roller  84 , at the predetermined circumferential position of the first feeding roller  84 . As a result, the two kinds of material monomer are polymerized into the positive-electrode vapor-deposited polymer film  36  of polyurea continuously formed on the positive electrode collector foil  18  formed of the aluminum foil tape  80 , while at the same time the positive electrode active substance  34  is introduced into the positive-electrode vapor-deposited polymer film  36 . 
     Then, the positive-electrode vapor-deposited polymer film  36  containing the positive electrode active substance  34  is irradiated with the ultraviolet radiation generated from the ultraviolet irradiating device  108 , so that the polyurea constituting the vapor-deposited polymer film  36  is transformed into polyaniline. Thus, the positive electrode active substance layer  20  formed of the positive-electrode vapor-deposited polymer film  36  of polyaniline containing the positive electrode active substance  34  is laminated integrally on the positive electrode collector foil  18  formed of the aluminum foil tape  80 . 
     It is noted that the mixture of the vapors of the two kinds of material monomer and the positive electrode active substance  34  is intermittently blown onto one of the opposite surfaces of the aluminum foil tape  80 , by the automatic alternate opening and closing actions of the above-described shut-off valve  123  at the predetermined time interval. It is also noted that the above-indicated mixture is intermittently blown onto the other surface of the aluminum foil tape  80 , by the automatic alternate opening and closing action of the shut-off valve  123  as described below. 
     Accordingly, segments of the positive electrode active substance layer  20  are laminated on the opposite surfaces of the aluminum foil tape  80 , such that the segments are spaced apart from each other by a predetermined spacing distance in the direction of length (in the direction of feeding) of the aluminum foil tape  80 , as shown in  FIG. 4 , such that the corresponding segments on the opposite surfaces of the aluminum foil tape  80  are located at the same position in the longitudinal direction, and such that the aluminum foil tape  80  is provided with active-substance-free portions  61  each formed between the adjacent segments of the positive electrode active substance layer  20  laminated on each of the opposite surfaces of the aluminum foil tape  80 . Namely, the positive electrode active substance layer  20  is absent in the active-substance-free portions  61 . In the present embodiment, the mixture of the two kinds of material monomer and the positive electrode active substance  34  is blown onto only a widthwise central or intermediate portion of each of the opposite surfaces of the aluminum foil tape  80 , so that the positive-electrode vapor-deposited polymer film  36  is not formed in the widthwise end portions of the opposite surfaces of the aluminum foil tape  80 , but is formed in only the widthwise central portions. 
     Subsequently, the mixture of the vapors of the three kinds of material monomer generated in the first, second and third vapor sources  132 ,  134  and  136  of the first inner vapor-deposited polymer film forming unit  90 , and the lithium-ion conductivity rendering substance  152  fed from the lithium salt introducing device  130  into the vapor supply pipe  138  together with the carrier gas, is continuously blown from the outlet open end of the vapor supply pipe  138  and deposited onto the positive electrode active substance layer  20  formed on one of the opposite surfaces of the aluminum foil tape  80  being fed in rolling contact with the first feeding roller  84 . 
     As a result, the three kinds of material monomer are polymerized into the first inner vapor-deposited polymer film  42  formed of polyurea having the repeating unit structure of polyethylene oxide and the functional group including the element of high electronegativity, on the positive electrode active substance layer  20  formed on the aluminum foil tape  80 , while at the same time the lithium-ion conductivity rendering substance  152  is introduced into the first inner vapor-deposited polymer film  42 . Thus, the first inner vapor-deposited polymer film  42  formed of polyurea having the lithium-ion conductivity and the functional group including the element of high electronegativity is laminated integrally on the positive electrode active substance layer  20  laminated on one of the opposite surfaces of the positive electrode collector foil  18  formed of the aluminum foil tape  80 . 
     In the present process, the three kinds of material monomer are blown not only on the positive electrode active substance layer  20 , but also on the active-substance-free portions  61  not covered by the positive electrode active substance layer  20 , and two width portions of the aluminum foil tape  80  on the respective opposite sides of the positive electrode active substance layer  20 , which two width portions are spaced apart from each other in the width direction of the aluminum foil tape  80  and which do not include one widthwise end portion of the aluminum foil tape  80 . Accordingly, the first inner vapor-deposited polymer film  42  is laminated integrally on the entire area of one of the opposite surfaces of the aluminum foil tape  80  except the above-indicated one widthwise end portion. 
     Then, the mixture of the vapors of the three kinds of material monomer generated in the first, second and third vapor sources  132 ,  134  and  136  of the first outer vapor-deposited polymer film forming unit  92 , and the lithium-ion conductivity rendering substance  152  fed from the lithium salt introducing device  156  into the vapor supply pipe  138  together with the carrier gas, is blown from the outlet open end of the vapor supply pipe  138  and deposited on the first inner vapor-deposited polymer film  42  formed on the positive electrode active substance layer  20  formed on the aluminum foil tape  80  moving in rolling contact with the outer circumferential surface of the first feeding roller  84 . 
     As a result, the first outer vapor-deposited polymer film  44  consisting of the polyurea having the repeating unit structure of polyethylene oxide is formed on the first inner vapor-deposited polymer film  42 , by polymerization of the three kinds of material monomer, while at the same time the lithium-ion conductivity rendering substance  152  is introduced into the first outer vapor-deposited polymer film  44 . Thus, the first outer vapor-deposited polymer film  44  formed of the polyurea having the lithium-ion conductivity is laminated integrally on the first inner vapor-deposited polymer film  42  formed on the positive electrode active substance layer  20  formed on the positive electrode collector foil  18  formed of the aluminum foil tape  80 . In the present process, the first outer vapor-deposited polymer film  44  is laminated integrally on the entire area of the surface of the first inner vapor-deposited polymer film  42  remote from the positive electrode active substance layer  20 . 
     As described above, the segments of the positive electrode active substance layer  20 , and the first inner and outer vapor-deposited polymer films  42  and  44  constituting the first solid electrolyte layer  24  are integrally laminated in this order of description on one of the opposite surfaces of the positive electrode collector foil  18  formed of the aluminum foil tape  80 . The positive electrode collector foil  18  on which the positive electrode active substance layer  20  and the first inner and outer vapor-deposited polymer films  42  and  44  have been formed is fed from the first feeding roller  84  toward the second feeding roller  86 . The segments of the positive electrode active substance layer  20  are formed in the widthwise central portion of the above-indicated one surface of the positive electrode collector foil  18 , at a predetermined spacing interval in the longitudinal direction of the aluminum foil tape  80 , while the first solid electrolyte layer  24  is formed continuously on the entire area of the above-indicated surface of the positive electrode collector foil  18  except the above-indicated one widthwise end portion. 
     Then, the positive electrode active substance layer  20  and the first solid electrolyte layer  24  are laminated in the same manner as described above, integrally on the other surface of the positive electrode collector foil  18  remote from the outer circumferential surface of the second feeding roller  86 , while the positive electrode collector foil  18  is fed by the second feeding roller  86  such that the above-indicated one surface of the collector foil  18  on which the positive electrode active substance layer  20  and the first solid electrolyte layer  24  have been formed is held in rolling contact with the outer circumferential surface of the second feeding roller  86 . 
     As described above, the positive electrode sheet  12  is continuously formed by laminating the positive electrode active substance layer  20  and the first solid electrolyte layer  24  consisting of the first inner and outer vapor-deposited polymer films  42  and  44 , in this order of description, integrally on each of the opposite surfaces of the positive electrode collector foil  18  formed of the aluminum foil tape  80 . The thus formed positive electrode sheet  12  is continuously fed from the second feeding roller  86  toward the laminar sheet forming unit  78 . In this respect, it is noted that the segments of the positive electrode active substance layer  20  and the first solid electrolyte layer  24  formed on one of the opposite surfaces of the positive electrode sheet  12  are located at the same positions in the width direction of the positive electrode sheet  12 , as those formed on the other surface of the positive electrode sheet  12 , so that one of the widthwise opposite end portions of the positive electrode collector foil  18  extends from the corresponding widthwise end face of the positive electrode sheet  12 , while the four end faces of each segment of the positive electrode active substance layer  20  are covered by the first solid electrolyte layer  24 , as shown in  FIGS. 2 and 4 . 
     While the positive electrode sheet  12  is continuously formed by the positive electrode sheet forming unit  74  as described above, the negative electrode sheet  14  is continuously formed by the negative electrode sheet forming unit  76  in substantially the same manner of formation of the positive electrode sheet  12 . Namely, segments of the negative electrode active substance layer  28  and the second solid electrolyte layer  32  are laminated integrally on each of the opposite surfaces of the negative electrode collector foil  26  formed of the copper foil tape  82 , in substantially the same manner of lamination of the positive electrode active substance layer  20  and the first solid electrolyte layer  24  of the positive electrode sheet  12 , whereby the negative electrode sheet  14  is formed. The thus formed negative electrode sheet  14  is continuously fed from the second feeding roller  96  toward the laminar sheet forming unit  78 . 
     Subsequently, the positive and negative electrode sheets  12  and  14  fed to the laminar sheet forming unit  78  are passed through the nip between the pair of laminating rollers  170 , so that the positive and negative electrode sheets  12  and  14  are superposed or laminated on each other, with the first and second solid electrolyte layers  24  and  32  being held in contact with each other, such that the active-substance-free portions  61  of the positive electrode collector foil  18  and the active-substance-free portions  61  of the negative electrode collector foil  26  are aligned with each other (such that the segments of the positive electrode active substance layer  20  and the segments of the negative electrode active substance layer  28  are aligned with each other). Thus, the laminar sheet  16  in the form of a tape is obtained, and is wound as a roll on the take-up roller  172 . It is noted that the positive electrode sheet  12  and the negative electrode sheet  14  are preferably superposed on each other such that these electrode sheets  12  and  14  are offset with respect to each other in the width direction. 
     The thus produced tape of the laminar sheet  16  is fed from the roll on the take-up roller  172 , and is cut into pieces at the positions of the tapes  80  and  82  corresponding to the active-substance-free portions  61  of the positive and negative electrode collector foils  18  and  26 . Each of the thus obtained pieces is the lithium-ion secondary battery  10  in the form of a laminar body consisting of the laminar sheets  16  having a structure shown in  FIG. 1 . The lithium-ion secondary battery  10  is generally used as a battery pack having a construction as shown in  FIG. 2  by way of example. 
     It will be understood from the foregoing description of the present embodiment that a step of forming the positive electrode sheet  12  and the negative electrode sheet  14  and a step of superposing these positive and negative electrode sheets  12  and  14  to produce the laminar sheet  16  are continuously performed as a series of operations within the vacuum chamber  64 , for continuously producing the desired lithium-ion secondary battery  10  in a roll-to-roll transferring fashion, so that the productivity of the lithium-ion secondary battery  10  can be significantly and effectively improved. 
     Further, the present lithium-ion secondary battery  10  in which the plurality of laminar sheets  16  are laminated on each other does not have portions in which the two positive electrode collector foils  18  are superposed on each other, or portions in which the two negative electrode collector foils  26  are superposed on each other, unlike a lithium-ion secondary battery consisting of a plurality of laminar sheets each consisting of a positive electrode sheet in which a positive electrode active substance layer and a first solid electrolyte layer are integrally laminated on only one of the opposite surfaces of a positive electrode collector foil, and a negative electrode sheet in which a negative electrode active substance layer and a second solid electrolyte layer are integrally laminated on only one of the opposite surfaces of a negative electrode collector foil. Accordingly, the amount of the positive electrode collector foils  18  and the negative electrode collector foils  26  required for the present lithium-ion secondary battery  10  can be effectively reduced, so that the required material cost can be effectively reduced. 
     The present lithium-ion secondary battery  10  is further configured such that the positive and negative electrode active substance layers  20  and  28  and the first and second solid electrolyte layers  24  and  32  are constituted by the positive-electrode vapor-deposited polymer film  36 , the negative-electrode vapor-deposited polymer film  40 , the first inner and outer vapor-deposited polymer films  42  and  44 , and the second inner and outer vapor-deposited polymer films  46  and  48 , which are formed of polyaniline or polyurea having a high degree of flexibility or plasticity. Accordingly, the lithium-ion secondary battery  10  does not have any gaps preventing movements of lithium ions during its charging and discharging, between the positive electrode collector foil  18  and the positive electrode active substance layer  20 , between the positive electrode active substance layer  20  and the first solid electrolyte layer  24 , between the negative electrode collector foil  26  and the negative electrode active substance layer  28 , and between the negative electrode active substance layer  28  and the second solid electrolyte layer  32 . Accordingly, interface resistances between the first solid electrolyte layer  24  and the positive electrode active substance layer  20 , and between the second solid electrolyte layer  32  and the negative electrode active substance layer  28  can be effectively reduced, resulting in an extremely advantageous improvement of the cell performance of the lithium-ion secondary battery  10 . In addition, the lithium-ion secondary battery  10  as a whole exhibits an adequate degree of flexibility or plasticity, and an accordingly high degree of bending or flexural strength. Accordingly, the lithium-ion secondary battery  10  has an effectively improved ease of handling. 
     In the present lithium-ion secondary battery  10 , a lamination boundary  50  is formed between the first and second solid electrolyte layers  24  and  32  which are laminated on each other. During charging and discharging of the lithium-ion secondary battery  10 , however, substantially no movements of the lithium ions take place between the first and second solid electrolyte layers  24  and  32 , so that the cell performance is not lowered in the presence of the lamination boundary  50 . 
     The present embodiment is also configured such that the positive and negative electrode active substance layers  20  and  28 , and the first and second solid electrolyte layers  24  and  32  are formed by the vapor-deposition polymerization process, so that each of the positive electrode active substance layer  20 , first solid electrolyte layer  24 , negative electrode active substance layer  28  and second solid electrolyte layer  32  can be formed with a sufficiently small thickness with a high degree of uniformity, on the opposite surfaces of the positive electrode collector foil  18  and the negative electrode collector foil  26 , even where the surfaces of these collector foils  18  and  26  are not sufficiently flat, in the presence of local recessed and raised portions formed therein or thereon, for instance. Therefore, irrespective of the condition of the surfaces of the positive and negative electrode collector foils  18  and  26 , the present lithium-ion secondary battery  10  has a high degree of stability of its cell performance, with effective reduction of its size and significant improvement of its output density and freedom from its geometrical restrictions. 
     Further, the vapor-deposition polymerization process employed to form the positive and negative electrode active substance layers  20  and  28  and the first and second solid electrolyte layers  24  and  32  is a vacuum dry process, so that there is no need to use a device for drying the positive and negative electrode active substance layers  20  and  28  and the first and second solid electrolyte layers  24  and  32  after these layers are formed, and it is possible to accordingly simplify the required production apparatus and to reduce its size, resulting in advantageous reduction of the running cost of the production apparatus. In addition, the elimination of the drying step and the vapor-deposition polymerization process which permits a sufficiently high rate of film formation assure extremely effective reduction of the required cycle time of production of the lithium-ion secondary battery  10 , so that the desired lithium-ion secondary battery  10  can be efficiently produced at a sufficiently reduced cost according to the present embodiment. 
     Further, the present lithium-ion secondary battery  10  is configured such that the first inner vapor-deposited polymer film  42  constituting a portion of the first solid electrolyte layer  24  on the side of the positive electrode active substance layer  20 , and the second inner vapor-deposited polymer film  46  constituting a portion of the second solid electrolyte layer  32  on the side of the negative electrode active substance layer  28  are formed of polyurea having the functional group including an element of high electronegativity, so that lithium ions exist with a higher density in the inner portions of the first and second solid electrolyte layers  24  and  32  on the side of the positive and negative electrode active substance layers  20  and  28 , whereby the cell performance is further improved. 
     The present lithium-ion secondary battery  10  is produced by cutting the tape of the laminar sheet  16  into pieces, at the active-substance-free portions  61  of the positive electrode collector foil  18  and the active-substance-free portions  61  of the negative electrode collector foil  26 , which are aligned with each other in the longitudinal direction of the tape. Accordingly, it is possible to effectively prevent short-circuiting between the positive electrode  22  and the negative electrode  30 , during cutting of the tape of the laminar sheet  16 , so that the lithium-ion secondary battery  10  has a high degree of stability of its cell performance. 
     Although the present lithium-ion secondary battery  10  is configured such that the lithium ions exist with a higher density in the inner portions of the first and second solid electrolyte layers  24  and  32  on the side of the positive and negative electrode active substance layers  20  and  28 , the lithium-ion secondary battery  10  may be further configured such that anions exist with a sufficiently low density in those inner portions of the first and second solid electrolyte layers  24  and  32 , in order to effectively prevent the anions from disturbing the movements of the lithium ions between the positive electrode active substance  34  in the positive electrode active substance layer  20  and the first solid electrolyte layer  24 , and between the negative electrode active substance  38  in the negative electrode active substance layer  28  and the second solid electrolyte layer  32 , for thereby further improving the cell performance. 
     In the present embodiment, the first solid electrolyte layer  24  has a two-layer structure consisting of the first inner vapor-deposited polymer film  42  and the first outer vapor-deposited polymer film  44 , while the second solid electrolyte layer  32  has a two-layer structure consisting of the second inner vapor-deposited polymer film  46  and the second outer vapor-deposited polymer film  48 . However, the lithium-ion secondary battery  10  may be replaced by a lithium-ion secondary battery  171  shown in  FIG. 5 , wherein the first solid electrolyte layer  24  is a single-layer structure consisting solely of a positive electrode vapor-deposited polymer film  172  formed integrally on the positive electrode active substance layer  20  by the vacuum vapor-deposition polymerization process, while the second solid electrolyte layer  32  has a single-layer structure consisting solely of a negative electrode vapor-deposited polymer film  174  formed integrally on the negative electrode active substance layer  28  by the vacuum vapor-deposition polymerization process. In this modified embodiment of the invention, the lithium ions and the anions are distributed evenly in the first and second solid electrolyte layers  24  and  32 , such that those ions exist with a substantially the same density in the thickness portions of the first solid electrolyte layer  24  relatively adjacent to and remote from the positive electrode active substance layer  20 , and in the thickness portions of the second solid electrolyte layer  32  relatively adjacent to and remote from the negative electrode active substance layer  28 . 
     The lithium-ion secondary battery  171  wherein the first solid electrolyte layer  24  consists solely of the positive electrode vapor-deposited polymer film  172  while the second solid electrolyte layer  32  consists solely of the negative electrode vapor-deposited polymer film  174  is produced by using a production apparatus  176  constructed as shown in  FIG. 6 , in substantially the same manner as described above with respect to the production of the lithium-ion secondary battery  10  according to the first embodiment. 
     The production apparatus  176  used to produce the present lithium-ion secondary battery  171  includes a positive electrode vapor-deposited polymer film forming unit  180 , and a negative-electrode vapor-deposited polymer film forming unit  184 . The positive electrode vapor-deposited polymer film forming unit  180  consists of a positive electrode vapor-deposited polymer film forming device  178  and the lithium salt introducing device  130 , while the negative electrode vapor-deposited polymer film forming unit  184  consists of a negative electrode vapor-deposited polymer film forming device  182  and the lithium salt introducing device  164 . The positive electrode vapor-deposited polymer film forming device  178  and the lithium salt introducing device  130  of the positive electrode vapor-deposited polymer film forming unit  180  have the same constructions as the first inner vapor-deposited polymer film forming device  128  and the lithium salt introducing device  130  of the first inner vapor-deposited polymer film forming unit  90  in the production apparatus  62  used to produce the lithium-ion secondary battery  10  according to the first embodiment, and the negative electrode vapor-deposited polymer film forming device  182  and the lithium salt introducing device  164  of the negative electrode vapor-deposited polymer film forming unit  184  have the same constructions as the second inner vapor-deposited polymer film forming device  162  and the lithium salt introducing device  164  of the second inner vapor-deposited polymer film forming unit  100  in the production apparatus  62 . The components of the present production apparatus  176  other than the positive electrode and negative electrode vapor-deposited polymer film forming units  180  and  184  are identical in construction with those of the production apparatus  62 , and are denoted in  FIG. 6  by the same reference signs as used in  FIG. 3 . Those components will not be described redundantly. 
     As previously described, the first and second solid electrolyte layers  24  and  32  are formed of the “resin A” which has a repeating unit structure of polyethylene oxide, which contains a lithium salt in polyethylene oxide, and which can be formed into a film by the vapor-deposition polymerization process, or the “resin B” which contains a lithium salt, a side chain of which is bonded to a sulfonic acid group, and which can be formed into a film by the vapor-deposited polymerization process. Therefore, the first and second solid electrolyte layers  24  and  32  can be formed by the production apparatus  176  in the following manner. These first and second solid electrolyte layers  24  and  32  can be formed in the same process by the positive electrode sheet forming unit  74  and the negative electrode sheet forming unit  76  which are identical in construction with each other. For this reason, the formation of only the first solid electrolyte layer  24  will be described. 
     In the case of formation of the first solid electrolyte layer  24  of polyurea in the form of the resin A, for example, the monomer reservoirs of the first and second vapor sources  132  and  134  of the positive electrode vapor-deposited polymer film forming device  178  of the positive electrode vapor-deposited polymer film forming unit  180  respectively accommodate the material monomer consisting of ethylene glycol diamine such as diethylene glycol bis(3-aminopropyl)ether, and the material monomer consisting of aromatic diisocyanate such as m-xylylene diisocyanate, at least one of which has a side chain bonded to the repeating unit structure of polyethylene oxide. In this case, the third vapor source  136  is not used. 
     The vapors of the material monomers generated in the respective first and second vapor sources  132  and  134  are polymerized on the positive electrode active substance layer  20  formed on the aluminum foil tape  80  being moved in rolling contact with the outer circumferential surface of the first feeding roller  84  within the vacuum chamber  64 , to form the positive electrode vapor-deposited polymer film  172 , while at the same time the powdered lithium-ion conductivity rendering substance  152  in the form of a lithium salt is introduced by the lithium salt introducing device  130  into the positive electrode vapor-deposited polymer film  172 . Thus, the positive electrode vapor-deposited polymer film  172  having the repeating unit structure of polyethylene oxide and containing the lithium salt in polyethylene oxide is formed on the positive electrode active substance layer  20  formed on the aluminum foil tape  80 , whereby the first solid electrolyte layer  24  is laminated integrally on the positive electrode active substance layer  20 . 
     In the case of formation of the first solid electrolyte layer  24  of polyurea in the form of the resin B, for example, the monomer reservoirs of the first and second vapor sources  132  and  134  of the positive electrode vapor-deposited polymer film forming device  178  of the positive electrode vapor-deposited polymer film forming unit  180  respectively accommodate the material monomer consisting of ethylene glycol diamine such as diethylene glycol bis(3-aminopropyl)ether, and the material monomer consisting of aromatic diisocyanate such as m-xylylene diisocyanate, at least one of which has a side chain bonded to a sulfonic acid group. In this case, the third vapor source  136  is not used, either. 
     The vapors of the material monomers generated in the respective first and second vapor sources  132  and  134  are polymerized on the positive electrode active substance layer  20  formed on the aluminum foil tape  80  being moved in rolling contact with the outer circumferential surface of the first feeding roller  84  within the vacuum chamber  64 , to form the positive electrode vapor-deposited polymer film  172 , while at the same time the powdered lithium-ion conductivity rendering substance  152  in the form of the lithium salt is introduced by the lithium salt introducing device  130  into the positive electrode vapor-deposited polymer film  172 . Thus, the positive electrode vapor-deposited polymer film  172  containing the lithium salt and having a side chain bonded to a sulfonic acid group is formed on the positive electrode active substance layer  20 , whereby the first solid electrolyte layer  24  is laminated integrally on the positive electrode active substance layer  20 . 
     By the way, the kind of the lithium-ion conductivity rendering substance  152  is not particularly limited, provided this substance  152  can literally render lithium-ion conductivity to the first and second solid electrolyte layers  24  and  32 , when the substance  152  is contained in these solid electrolyte layers  24  and  32 . Hence, it is possible to use, as the lithium-ion conductivity rendering substance  152 , an ion-conductive polymer in which a lithium salt is dissolved. Where this ion-conductive polymer is used, the desired lithium-ion secondary battery  171  can be produced by using a production apparatus  186  constructed as shown in  FIG. 7  according to a third embodiment of this invention, for example. 
     As shown in  FIG. 7 , the production apparatus  186  is identical in construction with the production apparatus  176  of the second embodiment shown in  FIG. 6 , except in the construction of the positive electrode and negative electrode vapor-deposited polymer film forming units  180  and  184 . Since these vapor-deposited polymer film forming units  180  and  184  are identical in construction with each other, only the positive electrode vapor-deposited polymer film forming unit  180  will be described in connection with the production apparatus  186 . 
     Namely, the positive electrode vapor-deposited polymer film forming unit  180  of the production apparatus  186  has a positive electrode vapor-deposited polymer film forming device  188  which is not provided with the third vapor source ( 136 ). The monomer reservoirs of the first and second vapor sources  132  and  134  of the positive electrode vapor-deposited polymer film forming device  188  respectively accommodate ethylene glycol diamine such as diethylene glycol bis(3-aminopropyl)ether, and aromatic diisocyanate such as m-xylylene diisocyanate, for example, in a liquid state, as the two kinds of material monomer for the positive electrode vapor-deposited polymer film  172  formed of polyuria. 
     In the positive electrode vapor-deposited polymer film forming device  188 , the vapors of the two kinds of material monomer are generated by heating the monomer reservoirs of the first and second vapor sources  132  and  134  by the heaters, and the generated vapors are supplied through the vapor supply pipe  138  into the vacuum chamber  64 , and blown onto the positive electrode active substance layer  20  formed on the aluminum foil tape  80  being moved in rolling contact with the outer circumferential surface of the first feeding roller  84 . 
     The production apparatus  186  has a lithium salt introducing device  192  including the gas cylinder  140 , the gas supply pipe  144 , the mass flow controller  146 , a liquid reservoir  194 , and a liquid supply pipe  196 . The liquid reservoir  194  of the lithium salt introducing device  192  accommodates the lithium-ion conductivity rendering substance  152  consisting of an ion-conductive polymer in a liquid state at the ambient temperature, in which a lithium salt is dissolved. In the third embodiment, oligo-ethylene oxide in which a lithium salt [LiN(SO 2 CF 3 ) 2 , for example] is dissolved and which has a low molecular weight of about not more than 700 is used as the lithium-ion conductivity rendering substance  152 . 
     The liquid supply pipe  196  has an outlet end portion inserted into the gas supply pipe  144 , which,has an outlet end portion which is inserted into and located within the vapor supply pipe  138  of the positive electrode vapor-deposited polymer film forming device  188 , so that the outlet end portion of the gas supply pipe  144  is open toward the outer circumferential surfaces of the first feeding roller  84  and the second feeding roller  86 , through the outlet end portion of the vapor supply pipe  138 . 
     In the lithium salt introducing device  192  having the structure described above, the carrier gas is fed from the gas cylinder  140  through the gas supply pipe  144 , in the open state of the shut-off valve, while the lithium-ion conductivity rendering substance  152  accommodated in a liquid state in the liquid reservoir  194  is sucked into the gas supply pipe  144  through the liquid supply pipe  196 , under a reduced pressure generated within the gas supply pipe  144 . Further, the liquid lithium-ion conductivity rendering substance  152  is dispersed in a mist state in the carrier gas within the gas supply pipe  144 , and is fed into the outlet end portion of the vapor supply pipe  138 , together with the carrier gas. Micro particles of the lithium-ion conductivity rendering substance  152  in the mist state are mixed with the vapors of the two kinds of material monomer in the outlet end portion of the vapor supply pipe  138 , and a mixture of the particles of the substance  152 , the vapors of the two kinds of material monomer and the carrier gas is blown from the outlet open end of the vapor supply pipe  138 , onto the aluminum foil tape  80  being moved in rolling contact with the outer circumferential surfaces of the first and second feeding rollers  84  and  86 . Thus, the lithium salt introducing device  192  is configured to introduce the lithium-ion conductivity rendering substance  152  into the positive electrode vapor-deposited polymer film  172  formed by the positive electrode vapor-deposited polymer film forming device  188  as described below. 
     The negative electrode vapor-deposited polymer film forming unit  184  also has a negative electrode vapor-deposited polymer film forming device  190  and the lithium salt introducing device  192 , which are identical in construction with the positive electrode vapor-deposited polymer film forming device  188  and the lithium salt introducing device  192  of the positive electrode vapor-deposited polymer film forming unit  180 . 
     The desired lithium-ion secondary battery  171  is produced by the thus constructed production apparatus  186 , in the following manner. 
     After the preparatory operation for production of the lithium-ion secondary battery  10 , the steps of forming the positive and negative electrode active substance layers  20  and  28  on the aluminum and copper foil tapes  80  and  82  being moved in rolling contact with the outer circumferential surfaces of the first and second feeding rollers  84 ,  94  and  86 ,  96  are performed in the same manner as in the production of the lithium-ion secondary battery  171  by the production apparatus  176  of the second embodiment. 
     Then, the mixture of the vapors of the two kinds of material monomer generated in the first and second vapor sources  132  and  134 , and the lithium-ion conductivity rendering substance  152  blown from the lithium salt introducing device  192  into the vapor supply pipe  138  together with the carrier gas is blown from the outlet open end of the vapor supply pipe  138  onto each of the positive electrode active substance layers  20  formed on the respective opposite surfaces of the aluminum foil tape  80  being moved in rolling contact with the outer circumferential surfaces of the first and second feeding rollers  84  and  86 , so as to polymerize the two kinds of material monomer on the positive electrode active substance layer  20 , for thereby forming the positive electrode vapor-deposited polymer film  172  of polyurea, while at the same time the lithium-ion conductivity rendering substance  152  is introduced into the positive electrode vapor-deposited polymer film  172 , whereby the positive electrode sheet  12  is produced. The negative electrode sheet  14  is produced in the same manner as the positive electrode sheet  12 . 
     The thus produced positive and negative electrode sheets  12  and  14  are superposed or laminated on each other and wound as a roll of the laminar sheet  16 , by the laminar sheet forming unit  78 . Then, the roll of the laminar sheet  16  is cut in the circumferential direction, to obtain the desired lithium-ion secondary battery  171 . 
     The present third embodiment has substantially the same operational and physical advantages as the first and second embodiments described above. 
     Referring next to the fragmentary longitudinal cross sectional view of  FIG. 8 , there is shown a lithium-ion secondary battery  198  according to a fourth embodiment of the present invention. As shown in  FIG. 8 , the lithium-ion secondary battery  198  has a positive-electrode-side mixture layer  200  interposed between each of the positive electrode active substance layers  20  formed on the respective opposite surfaces of the positive electrode collector foil  18 , and the corresponding first solid electrolyte layer  24 , and a negative-electrode-side mixture layer  202  interposed between each of the negative electrode active substance layers  28  formed on the respective opposite surfaces of the negative electrode collector foil  26 , and the corresponding second solid electrolyte layer  32 . In the present embodiment, the positive-electrode vapor-deposited polymer film  36  of the positive electrode active substance layer  20 , and the negative-electrode vapor-deposited polymer film  40  of the negative electrode active substance layer  28  are formed of polyurethane, and the first solid electrolyte layer  24  is constituted by the positive electrode vapor-deposited polymer film  172  formed of polyurea having a repeating unit structure of polyethylene oxide and containing a lithium salt in polyethylene oxide, while the second solid electrolyte layer  32  is constituted by the negative electrode vapor-deposited polymer film  174  formed of polyurea having a repeating unit structure of polyethylene oxide and containing a lithium salt in the polyethylene oxide. 
     The positive-electrode-side mixture layer  200  is formed of a mixture of a first polymer of polyurethane used to form the positive electrode active substance layer  20 , and a second polymer of polyurea used to form the first solid electrolyte layer  24 , while the negative-electrode-side mixture layer  202  is formed of a mixture of a third polymer of polyurethane used to form the negative electrode active substance layer  28 , and a fourth polymer of polyurea used to form the second solid electrolyte layer  32 . The positive-electrode-side mixture layer  200  and the negative-electrode-side mixture layer  202  also contain the lithium-ion conductivity rendering substance  152  as needed. Those positive-electrode-side and negative-electrode-side mixture layers  200  and  202  are electrically conductive. 
     In the positive-electrode-side mixture layer  200 , the content of polyurethane gradually decreases in the direction from the positive electrode active substance layer  20  toward the first solid electrolyte layer  24 , while the content of polyurea gradually increases in the direction from the positive electrode active substance layer  20  toward the first solid electrolyte layer  24 . In the negative-electrode-side mixture layer  202 , the content of polyurethane gradually decreases in the direction from the negative electrode active substance layer  28  toward the second solid electrolyte layer  32 , while the content of polyurea gradually increases in the direction from the negative electrode active substance layer  28  toward the second solid electrolyte layer  32 . Namely, the contents of polyurethane and polyurea in the positive-electrode-side mixture layer  200  and the negative-electrode-side mixture layer  202  change linearly in the direction from the positive and negative electrode active substance layers  20  and  28  toward the first and second solid electrolyte layers  24  and  32 . 
     For example, a production apparatus  204  shown in  FIG. 9  is suitably used to produce the lithium-ion secondary battery  198  having the structure described above. 
     In the production apparatus  204 , each of the vapor supply pipes  114  of the two positive electrode active substance layer forming units  88 , and each of the vapor supply pipes  138  of the two positive electrode vapor-deposited polymer film forming units  180  are positioned such that the vapor supply pipes  114  and  138  are open at their outlet ends toward the outer circumferential surfaces of the first and second feeding rollers  84  and  86 , as shown in  FIG. 9 . Similarly, each of the vapor supply pipes  114  of the two negative electrode active substance layer forming units  98 , and each of the vapor supply pipes  138  of the two negative electrode vapor-deposited polymer film forming units  184  are positioned such that the vapor supply pipes  114  and  138  are open at their outlet ends toward the outer circumferential surfaces of the first and second feeding rollers  94  and  96 . Each of the vapor supply pipes  114  is not provided at its outlet end portion with the shut-off valve  123 . In the other aspects, the present production apparatus  204  is identical in construction with the production apparatus  176  shown in  FIG. 6 . 
     The desired lithium-ion secondary battery  198  is produced by using the thus constructed production apparatus  204 , in the following manner. 
     Initially, the preparatory operation is carried out in the manner described above, and the vacuum chamber  64  is evacuated. On the other hand, the material monomers accommodated in the monomer reservoirs provided in each positive electrode active substance layer forming unit  88 , each negative electrode active substance layer forming unit  98 , each positive electrode vapor-deposited polymer film forming unit  180  and each negative electrode vapor-deposited polymer film forming unit  184  are heated, whereby the material monomers are vaporized. 
     The monomer reservoirs of the positive and negative electrode active substance layer forming units  88  and  98  respectively accommodate, as the material monomers, aromatic diol such as 1,3-dihydroxyl benzene in a liquid state, for example, and aromatic diisocyanate such as 1,4-phenylene diisocyanate in a liquid state, for example. The monomer reservoirs of the positive and negative vapor-deposited polymer film forming units  180  and  184  respectively accommodate ethylene glycol diamine such as diethylene glycol bis(3-aminopropyl)ether, aromatic diisocyanate such as m-xylylene diisocyanate, and olygo-ethylene oxide in a liquid or solid state, for example. 
     After the pressure within the vacuum chamber  64  has been adjusted to the predetermined level, the shut-off valves provided in the positive electrode active substance layer forming unit  88  positioned adjacent to the first feeding roller  84  of the positive electrode sheet forming unit  74  (that is, the shut-off valves provided at the connections of the monomer reservoirs to the vapor supply pipe  114 , and the shut-off valve provided in the gas cylinder  116  of the positive electrode active substance introducing device  106 ) are opened by a predetermined amount so that the mixture of the vapors of the two kinds of material monomer and the positive electrode active substance  34  is blown onto one of the opposite surfaces of the aluminum foil tape  80  being moved in rolling contact with the outer circumferential surface of the first feeding roller  84 . 
     After a predetermined length of time has passed, the amount of opening of the shut-off valves of the vapor supply pipe  114  and the shut-off valve of the gas cylinder  116  is gradually reduced to zero. Thus, the mixture of the vapors of the two kinds of material monomer and the positive electrode active substance  34  is supplied from the positive electrode active substance layer forming unit  88  into the vacuum chamber  64  (that is, the mixture is blown onto the aluminum foil tape  80  being moved in rolling contact with the outer circumferential surface of the first feeding roller  84 ), at a predetermined rate of supply for the predetermined length of time, and the rate of supply is gradually reduced to zero. In this respect, it is noted that the shut-off valve of the gas cylinder  116  may be fully closed at a moment of initiation of the closing actions of the shut-off valves of the vapor supply pipe  114 . 
     At the moment of initiation of the closing action of each of the shut-off valves of the positive electrode active substance layer forming unit  88 , or immediately before or after this moment of initiation, the shut-off valves provided in the positive electrode vapor-deposited polymer film forming unit  180  positioned adjacent to the first feeding roller  84  (that is, the shut-off valves provided at the connections of the monomer reservoirs to the vapor supply pipe  138 ) are opened such that the amount of opening is gradually increased to a predetermined value. After a predetermined length of time has passed, the shut-off valves of the positive electrode vapor-deposited polymer film forming unit  180  are closed. Thus, the rate of supply of the three kinds of material monomer from the positive electrode vapor-deposited polymer film forming unit  180  into the vacuum chamber  64  is gradually increased to a predetermined value. Then, the rate of supply is reduced to zero. In this respect, it is desirable to adjust the rate of closing of the shut-off valves of the positive electrode active substance layer forming unit  88  and the rate of opening of the shut-off valves of the positive electrode vapor-deposited polymer film forming unit  180 , so that the pressure within the vacuum chamber  64  is kept constant as much as possible. 
     While only the shut-off valves of the positive electrode active substance layer forming unit  88  are kept open by the predetermined amount as described above, polyurethane is generated on one of the opposite surfaces of the aluminum foil tape  80 , whereby the positive electrode active substance layer  20  of polyurethane is formed on one of the opposite surfaces of the positive electrode collector foil  18 . It is noted that the length of time during which the shut-off valves of the positive electrode active substance layer forming unit  88  are kept by the predetermined amount is suitably determined depending upon the thickness of the positive electrode active substance layer  20  to be formed. 
     Then, the shut-off valves of the positive electrode active substance layer forming unit  88  are gradually closed, while at the same time the shut-off valves of the positive electrode vapor-deposited polymer film forming unit  180  are gradually opened, so that the rate of generation of polyurethane on the positive electrode active substance layer  20  of the predetermined thickness is gradually reduced while the rate of generation of polyurea on the positive electrode active substance layer  20  is gradually increased. Subsequently, the amount of opening of the shut-off valves of the positive electrode vapor-deposited polymer film forming unit  180  is kept at a predetermined value for a predetermined length of time, so that the rate of generation of polyurea is kept at a predetermined value. 
     During a time period from the moment of initiation of the closing actions of the shut-off valves of the positive electrode active substance layer forming unit  88  to the moment at which the shut-off valves are fully closed so that the amounts of the two kinds of material monomer to be supplied from the positive electrode active substance layer forming unit  88  into the vacuum chamber  64  and left within the vacuum chamber  64  are eventually reduced to zero, the polymerization reaction of these two kinds of material monomer and the polymerization reaction of the three kinds of material monomer supplied from the positive electrode vapor-deposited polymer film forming unit  180  take place concurrently to form the positive-electrode-side mixture layer  200  having the structure described above on the positive electrode active substance layer  20 . Subsequently, the amount of opening of the shut-off valves of the positive electrode vapor-deposited polymer film forming unit  180  is kept at a predetermined value for a predetermined length of time, so that the positive electrode vapor-deposited polymer film  172  (rust solid electrolyte layer  24 ) having a predetermined thickness is laminated on the positive-electrode-side mixture layer  200 . 
     After the positive electrode active substance layer  20 , positive-electrode-side mixture layer  200  and first solid electrolyte layer  24  have been laminated integrally on one of the opposite surfaces of the aluminum foil tape  80  as described above, the aluminum foil tape  80  is partially wound on the second feeding roller  86  such that the surface of the aluminum foil tape  80  on which the layers  24 ,  200  and  24  have been laminated is in rolling contact with the outer circumferential surface of the second feeding roller  86 , and so that the positive electrode active substance layer  20 , positive-electrode-side mixture layer  200  and first solid electrolyte layer  24  are laminated integrally on the other of the opposite surfaces of the aluminum foil tape  80 , in the same manner as described above. Thus, the positive electrode sheet  12  is continuously formed. 
     Concurrently with the continuous formation of the positive electrode sheet  12 , the negative electrode active substance layer  28 , negative-electrode-side mixture layer  202  and second solid electrolyte layer  32  are laminated integrally on each of the opposite surfaces of the copper foil tape  86 , in this order of description, so that the negative electrode sheet  14  is continuously formed. This negative electrode sheet  14  is formed by using the negative electrode active substance layer forming units  98  and the negative electrode vapor-deposited polymer film forming units  184 , in substantially the same manner as described above with respect to the positive electrode sheet  12 . 
     Subsequently, the positive electrode sheet  12  and the negative electrode sheet  14  are laminated on each other by the laminar sheet forming unit  78 , and wound as a roll of the laminar sheet  16 . Then, the roll of the laminar sheet  16  is cut in the circumferential direction, to obtain the desired lithium-ion secondary battery  198 . 
     It will be understood from the foregoing description of the fourth embodiment that this embodiment has substantially the same operational and physical advantages as the several preceding embodiments. 
     The present fourth embodiment is configured to form the positive-electrode-side mixture layers  200  between the positive electrode active substance layers  20  and the first solid electrolyte layers  24 , and the negative-electrode-side mixture layers  202  between the negative electrode active substance layers  28  and the second solid electrolyte layers  32 , in the vacuum chamber  64  in a roll-to-roll transferring fashion. Accordingly, the positive and negative electrode active substance layers  20  and  28 , and the first and second solid electrolyte layers  24  and  32  do not have any distinct boundary interface therebetween, so that the lithium-ion secondary battery  198  having advantageously increased electron conductivity and ion conductivity and an advantageously improved output density can be stably and efficiently produced with a high degree of productivity. 
     By the way, the battery cell device  54  is formed by parallel connection of the cell elements of the lithium-ion secondary battery  10 ,  171  or  198  in each of the preceding embodiments. In a fifth embodiment shown in  FIG. 10  by way of example, however, a battery cell device  207  is formed by series connection of the cell elements of a lithium-ion secondary battery  206 . Since this lithium-ion secondary battery  206  has apparently the same configuration as the lithium-ion secondary battery  171  shown in  FIG. 5 , the lithium-ion secondary battery  206  will be described by reference to  FIG. 5 . 
     Namely, the lithium-ion secondary battery  206  according to the present fifth embodiment is constituted by the two laminar sheets  16  which are laminated on each other and each of which consists of the first electrode sheet  12  and the second electrode sheet  14  laminated on each other, such that the lithium-ion secondary battery  206  has three cell elements, as shown in  FIG. 5 . Since the first electrode sheet  12  and the second electrode sheet  14  have the same structure, only the structure of the first electrode sheet  12  will be described. 
     Described more specifically, the first electrode sheet  12  has a bipolar electrode  214  consisting of a collector foil  208 , and positive and negative electrode active substance layers  210  and  212  which are laminated integrally on the respective opposite surfaces of the collector foil  208 . Further, the first solid electrolyte layer  24  is laminated integrally on one of the opposite surfaces of the positive electrode active substance layer  210  of the bipolar electrode  214 , which surface is remote from the collector foil  208 , while the second solid electrolyte layer  32  is laminated integrally on one of the opposite surfaces of the negative electrode active substance layer  212  of the bipolar electrode  214 , which surface is remote from the collector foil  208 . 
     The collector foil  208  of the first electrode sheet  12  is a metallic foil, which is a nickel foil in the present embodiment. However, the metallic material of the collector foil  208  is not particularly limited, and may be of any kind that can be used as a bipolar electrode, without decomposition due to an electric potential difference. That is, metallic foils formed of copper, aluminum, and alloys of those metals, other than the nickel foil may be used as the collector foil  208 . Further, the collector foil  208  may consist of a plurality of metallic foil layers bonded together so as to permit electric conductivity. The metallic material of the collector foil  208  is suitably selected depending upon the kind of the positive electrode active substance  34  in the positive electrode active substance layer  210 , and the kind of the negative electrode active substance  38  in the negative electrode active substance layer  212 . For instance, the collector foil  208  is a clad material of copper and aluminum, or a metallic foil such as stainless steel foil, copper foil or nickel foil, where the positive electrode active substance  34  is LiCoO 2 , Li(Ni—Mn—Co)O 2  (Ni of which may be partially replaced by Co or Mn), LiNiO 2 , LiMn 2 O 4 , LiFePO 4 , LiMn x Fe 1-x PO 4 , or any other active substance having an electric potential of about 3-5V with respect to Li, while the negative electrode active substance  38  is a natural graphite, hard carbon, carbon nano tube, carbon nano wall, mesophase carbon micro bead, mesophase carbon fiber, lithium metal, lithium-aluminum alloy, intercalated lithium compound in which lithium is intercalated in graphite or carbon, Si, alloy of Si, Sn, alloy of Sn, or any other active substance having an electric potential of about 0-1V with respect to Li. Alternatively, the collector foil  208  may be a metallic foil such as aluminum foil, titanium foil and chrominum foil, other than the clad material of copper and aluminum, stainless steel foil, copper foil and nickel foil, where the positive electrode active substance  34  is LiCoO 2 , Li(Ni—Mn—Co)O 2  (Ni of which may be partially replaced by Co or Mn), LiNiO 2 , LiMn 2 O 4 , LiFePO 4 , LiMn x Fe 1-x PO 4 , or any other active substance having an electric potential of about 3-5V with respect to Li, while the negative electrode active substance  38  is LiTi 5 O 12 , MnO 2 , an oxide of Si, an oxide of Sn, or any other active substance having an electric potential of about 1-2V with respect to Li. 
     The positive and negative electrode active substance layers  210  and  212 , and the first and second solid electrolyte layers  24  and  32  have substantially the same structures as the positive and negative electrode active substance layers  20  and  28  and the first and second solid electrolyte layers  24  and  32  of the lithium-ion secondary battery  171  of the preceding second embodiment. 
     The lithium-ion secondary battery  206  having the structure described above is used as the battery cell device  207  covered by the two covering films  52 , as shown in  FIG. 10 . 
     Namely, the battery cell device  207  is provided with the two protective films  56  laminated on the respective opposite end faces of the lithium-ion secondary battery  206  which are opposed to each other in the direction of lamination of the two laminar sheets  16 . Further, the collector foil  208  of the first electrode sheet  12  located at one end (upper end as seen in  FIG. 10 ) of the lithium-ion secondary battery  206  is electrically connected to the positive terminal  58  in the form of a flat sheet, while the collector foil  208  of the second electrode sheet  14  located at the other end (lower end as seen in  FIG. 10 ) of the lithium-ion secondary battery  206  is electrically connected to the negative terminal  60  in the form of a flat sheet. Thus, the three cell elements of the lithium-ion secondary battery  206  are connected in series with each other. 
     A laminar body consisting of the lithium-ion secondary battery  206  and the protective films  56  is covered by the two covering films  52  such that the laminar body is sandwiched by and between the two covering films  52 . In this state, the end portion of the positive terminal  58  remote from the collector foil  208 , and the end portion of the negative terminal  60  remote from the collector foil  208  extend outwardly from the mutually connected end portions of the two covering films  52 . Thus, the battery cell device  207  wherein the lithium-ion secondary battery  206  is covered by the covering films  52  is formed. In  FIG. 10 , the battery cell device  207  is shown for easier understanding of its internal structure such that a space exists between the covering films  52  and the lithium-ion secondary battery  206 , as in  FIG. 2 . However, this space does not actually exist. 
     The battery cell device  207  having the structure described above is used alone, or a plurality of the battery cell devices  207  are connected in parallel or in series with each other so as to constitute a battery pack. 
     For instance, the lithium-ion secondary battery  206  having the structure described above is produced by using a production apparatus which is different in construction from the production apparatus  176  shown in  FIG. 6 , in the arrangement of the positive electrode active substance layer forming unit  88 , negative electrode active substance layer forming unit  98 , positive electrode vapor-deposited polymer film forming unit  180  and negative electrode vapor-deposited polymer film forming unit  184 . 
     Described more specifically referring back to  FIG. 6 , the production apparatus  176  used for production of the lithium-ion secondary battery  206  is configured such that one positive electrode active substance layer forming unit  88  and one positive electrode vapor-deposited polymer film forming unit  180  are disposed such that the outlet end portion of each of the vapor supply pipes  114  and  138  is open toward the outer circumferential surface of the first feeding roller  84  (of the positive electrode sheet forming unit  74 ), while one negative electrode active substance layer forming unit  98  and one negative electrode vapor-deposited polymer film forming unit  184  are disposed such that the outlet end portion of each of the vapor supply pipes  114  and  138  is open toward the outer circumferential surface of the second feeding roller  86  (of the positive electrode sheet forming unit  74 ). Further, another positive electrode active substance layer forming unit  88  and another positive electrode vapor-deposited polymer film forming unit  180  are disposed such that the outlet end portion of each of the vapor supply pipes  114  and  138  is open toward the outer circumferential surface of the first feeding roller  94  (of the negative electrode sheet forming unit  76 ), while another negative electrode active substance layer forming unit  98  and another negative electrode vapor-deposited polymer film forming unit  184  are disposed such that the outlet end portion of each of the vapor supply pipes  114  and  138  is open toward the outer circumferential surface of the second feeding roller  96  (of the negative electrode sheet forming unit  76 ). The rolls of a tape of the collector foil  208  such as a nickel foil are installed on the first supply roller  70  and the second supply roller  72 . 
     When the desired lithium-ion secondary battery  206  is produced by using the thus constructed production apparatus  176 , the positive electrode active substance layer  210  and the first solid electrolyte layer  24  constituted by the positive electrode vapor-deposited polymer film  172  are integrally laminated on each other in this order of description on one of the opposite surfaces of the collector foil  208  by the positive electrode active substance layer forming unit  88  and the positive electrode vapor-deposited polymer film forming unit  180 , while the tape of the collector foil  208  extending from the roll installed on the first supply roller  70  is moved in rolling contact with the outer circumferential surface of the first feeding roller  84 . 
     Then, the negative electrode active substance layer  212  and the second solid electrolyte layer  32  constituted by the negative electrode vapor-deposited polymer film  174  are integrally laminated on each other in this order of description on the other surface of the collector foil  208  by the negative electrode active substance layer forming unit  98  and the negative electrode vapor-deposited polymer film forming unit  184 , while the tape of the collector foil  208  fed from the first feeding roller  84  is moved in rolling contact with the outer circumferential surface of the second feeding roller  86 . Thus, the first electrode sheet  12  is continuously formed. 
     While the first electrode sheet  12  is continuously formed, the positive electrode active substance layer  210  and the first solid electrolyte layer  24  are integrally laminated on each other in this order of description on one of the opposite surfaces of the collector foil  208  extending from the roll installed on the second supply roller  72 , and the negative electrode active substance layer  212  and the second solid electrolyte layer  32  are integrally laminated on each other in this order of description on the other surface of the collector foil  208 , whereby the second electrode sheet  14  is continuously formed, in substantially the same manner as the first electrode sheet  12 . 
     Then, the first and second electrode sheets  12  and  14  are superposed or laminated on each other and wound as a roll of the laminar sheet  16 , by the laminar sheet forming unit  78 . Then, the roll of the laminar sheet  16  is cut in the circumferential direction, to obtain the desired lithium-ion secondary battery  206 . 
     The lithium-ion secondary battery  206  according to the present fifth embodiment has substantially the same operational and physical advantages as in the preceding several embodiments. In particular, the present lithium-ion secondary battery  206  is configured to advantageously permit the series connection of the cell elements with each other, and efficient production thereof with a reduced size and a simple structure, so as to assure a comparatively high withstand voltage. 
     In the method of producing the lithium-ion secondary battery  206  according to the present fifth embodiment, too, the shut-off valves  123  provided at the corresponding outlet end portions of the vapor supply pipes  114  and  138  of the positive and negative electrode active substance layer forming units  88  and  98  are alternately opened and closed at a predetermined time interval, so that the segments of the positive electrode active substance layer  210  are laminated on one of the opposite surfaces of the tape of the collector foil  208 , at the predetermined spacing interval in the longitudinal direction of the tape, while the segments of the negative electrode active substance layer  212  are laminated on the other surface of the tape, at the predetermined spacing interval in the longitudinal direction of the tape, as shown in  FIG. 4 . Accordingly, the electrode sheet  12  ( 14 ) can be formed such that the active-substance-free portion  61  is formed between the adjacent segments of the positive electrode active substance layer  210  and between the adjacent segments of the negative electrode active substance layer  212 . Thus, the lithium-ion secondary battery  206  has substantially the same operational and physical advantages as the lithium-ion secondary battery  10  of the first embodiment which also has the active-substance-free portions  61 . 
     The lithium-ion secondary battery  206  of this fifth embodiment may be modified such that each of the first and second solid electrolyte layers  24  and  32  consists of two layers as shown in  FIG. 1 . Further, the lithium-ion secondary battery  206  may be modified such that the positive-electrode-side mixture layer  200  is formed between the positive electrode active substance layer  210  and the first solid electrolyte layer  24 , while the negative-electrode-side mixture layer  202  is formed between the negative electrode active substance layer  212  and the second solid electrolyte layer  32 , as shown in  FIG. 8 . 
     While the embodiments of the present invention have been described above in detail, for illustrative purpose only, it is to be understood that the invention is not limited to the details of the illustrated embodiments. 
     The number of the laminar sheets  16  which constitute the lithium-ion secondary batteries  10 ,  171 ,  198 ,  206  may be suitably changed or selected. 
     The positive electrode collector foil  18 , negative electrode collector foil  26  and collector foil  208  may have a multiplicity of through-holes filled with the positive electrode active substance  34  or negative electrode active substance  38 . This modification assures an increased cell performance of the lithium-ion secondary battery. 
     The positive electrode collector foil  18 , negative electrode collector foil  26  and collector foil  208  need not be provided with the active-substance-free portions  61  on their opposite surfaces. Namely, the positive electrode active substance layer  20 ,  210  and the negative electrode active substance layer  28 ,  212  may be formed integrally on the opposite surfaces of the positive and negative electrode collector foils  18  and  26  or the collector foil  208 , so as to extend continuously in the longitudinal direction of the tapes. 
     Further, the powder supply pipes  122  and  148  and the gas supply pipes  120  and  144  may be disposed in parallel with the corresponding vapor supply pipes  114  and  138 , as long as the positive electrode active substance  34 , the negative electrode active substance  38  and the lithium-ion conductivity rendering substance  152  can be blown onto the positive and negative electrode collector foils  18  and  26 , together with the vapors of the different kinds of material monomers. In this case, the outlet end portions of the powder supply pipes  122  and  148  and the gas supply pipes  120  and  144  are preferably located upstream of the outlet end portions of the vapor supply pipes  114  and  138  in the direction of feeding of the tapes of the positive and negative electrode collector foils  18  and  26  by the first and second feeding rollers  84 ,  94  and  86 ,  96 , so that the positive electrode active substance  34 , negative electrode active substance  38  and lithium-ion conductivity rendering substance  152  can be stably mixed with the vapors of the different kinds of material monomer, before termination of polymerization of the material monomers. 
     It is to be understood that the present invention may be embodied with various other changes, modifications and improvements, which may occur to those skilled in the art, without departing from the spirit and scope of the invention defined by the appended claims. 
     
       
         
           
               
             
               
                   
               
               
                 NOMENCLATURE OF REFERENCE SIGNS 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 10, 171, 198, 206: Lithium-ion secondary battery 
                   
               
               
                 12: Positive electrode sheet 
                 14: Negative 
               
               
                   
                 electrode sheet 
               
               
                 16: Laminar sheet 
                 18: Positive 
               
               
                   
                 electrode collector 
               
               
                   
                 foil 
               
               
                 20, 210: Positive electrode active substance layer 
               
               
                 24: First solid electrolyte layer 
               
               
                 26: Negative electrode collector foil 
               
               
                 28, 212: Negative electrode active substance layer 
               
               
                 32: Second solid electrolyte layer 
                 34: Positive 
               
               
                   
                 electrode active 
               
               
                   
                 substance 
               
               
                 36: Positive electrode vapor-deposited polymer film 
               
               
                 38: Negative electrode active substance 
               
               
                 40: Negative electrode vapor-deposited polymer film 
               
               
                 50: Lamination boundary 
                 61: Active- 
               
               
                   
                 substance-free 
               
               
                   
                 portion 
               
               
                 208: Collector foil 
                 214: Bipolar 
               
               
                   
                 electrode