Patent Publication Number: US-11050120-B2

Title: Energy storage device

Description:
TECHNICAL FIELD 
     The present invention relates to an energy storage device equipped with a separator including an insulating layer on its surface. 
     BACKGROUND ART 
     Conventionally, an energy storage device equipped with an energy storage element has been known in which a separator is interposed between a positive electrode having a positive composite layer and a positive composite layer non-forming part and a negative electrode including a negative composite layer and a negative composite layer non-forming part. The positive composite layer non-forming part and the negative composite layer non-forming part are projected in opposite directions. 
     A material used for the separator (e.g., polypropylene, polyethylene, or the like) is contracted by heat to some extent. Accordingly, the separator is disposed to project more than ends of the positive composite layer and the negative composite layer to prevent short circuit between the positive electrode and the negative electrode due to heat contraction of the separator. 
     Patent Literature 1 focuses on a point that a positive electrode non coated portion side tends to be a high temperature as compared with a negative electrode non-coated portions side when the heat generated by overcharge or the like is stored inside a secondary battery. Patent Literature 1 discloses a secondary battery that appropriately prevents short circuit even when its temperature rises by making the projection amount of a separator on a positive electrode non-coated portion side be not less than two times of the projection amount of the separator on a negative electrode non coated portion side (paragraphs 0010, 0027, etc.). 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: JP-A-2012-043752 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     The inventor of the invention has found that the manufacturing time of the energy storage device can be shortened by causing electrolyte to efficiently penetrate into the positive composite layer in a process of injecting the electrolyte when the energy storage device equipped with a separator having an insulating layer on its surface opposing a positive electrode is manufactured. 
     An object of the invention is to shorten the manufacturing time of an energy storage device by causing electrolyte to efficiently penetrate into a positive composite layer in a process of injecting the electrolyte. 
     Means for Solving the Problems 
     A first aspect of the invention that aims to solve the above-mentioned problem is an energy storage device including: a negative electrode including a negative composite layer on a negative electrode collector foil and a negative composite layer non-forming part along a side of the negative electrode collector foil; a positive electrode including a positive composite layer on a positive electrode collector foil and a positive composite layer non-forming part along a side of the positive electrode collector foil; and a separator including an insulating layer on its surface opposing the positive electrode. The negative electrode and the positive electrode are layered with a separator interposed therebetween. The negative composite layer non-forming part and the positive composite layer non-forming part are disposed in opposite directions to each other. A part of the negative composite layer non-forming part is connected to a negative electrode current collector, and a part of the positive composite layer non-forming part is connected to a positive electrode current collector. An end S 1  on a side of the negative electrode current collector of the separator is projected more than an end P 1  on the side of the negative electrode current collector of the positive composite layer, and an end S 2  on a side of the positive electrode current collector of the separator is projected more than an end P 2  on the side of the positive electrode current collector of the positive composite layer. A distance W 2  from the end P 2  of the positive composite layer to the end S 2  of the separator is smaller than a distance W 1  from the end P 1  of the positive composite layer to the end S 1  of the separator. 
     The above-mentioned first aspect of the invention makes it possible to shorten the manufacturing time of the energy storage device by causing the electrolyte to efficiently penetrate into the positive composite layer in an injection process of the electrolyte. 
     Advantages of the Invention 
     The invention makes it possible to shorten the manufacturing time of the energy storage device equipped with the separator including the insulating layer on its surface opposing the positive electrode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating an energy storage device according to a first embodiment. 
         FIG. 2  is an exploded perspective view illustrating the energy storage device according to the first embodiment. 
         FIG. 3  is an exploded perspective view illustrating an energy storage element of the energy storage device according to the first embodiment. 
         FIG. 4  is a diagram illustrating a mode in which a positive electrode and a negative electrode are disposed with a constant interval with a separator interposed therebetween. 
         FIG. 5  is a cross sectional view in an X-Y plane of the energy storage element of the energy storage device according to the first embodiment. 
         FIG. 6  is a cross sectional view in the of the X-Y plane of the energy storage element of the energy storage device according to the first embodiment in a process of injecting electrolyte. 
         FIG. 7  is a schematic view illustrating plane Poiseuille flow in which the electrolyte flows between two parallel slabs. 
         FIG. 8  is a diagram illustrating a mode near an end of a positive composite layer on a positive composite layer non-forming part side of an energy storage device according to a third embodiment. 
         FIG. 9  is a diagram illustrating an energy storage apparatus equipped with a plurality of the energy storage devices according to the embodiments. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, embodiments of the invention will be described with reference to the drawings. The embodiments apply the invention to a lithium ion battery that is a nonaqueous electrolyte battery as an energy storage device. 
     First Embodiment 
     An energy storage device  1  according to a first embodiment will be described with reference to  FIG. 1  to  FIG. 7 . 
     The energy storage device  1  illustrated in  FIG. 1  is a nonaqueous electrolyte battery, specifically a nonaqueous electrolyte secondary battery, and more specifically a lithium ion battery. The energy storage device  1  is mounted on, for example, an electric vehicle (EV) or a hybrid vehicle (HEV), and supplies electric power to a power source that operates with electric energy. 
     As illustrated in  FIG. 2 , the energy storage device  1  includes an energy storage element  3  that is housed in an outer case  2  with nonaqueous electrolyte not shown in the drawing. A liquid like electrolyte is used as the electrolyte of the invention. 
     The outer case  2  has a case body  21  and a lid  22 . The case body  21  has a substantially rectangular parallelepiped shape as a whole, and an opening is formed on its upper end surface side. The case body  21  can be made of a metal such as aluminum or an aluminum alloy. The case body  21  includes a bottom wall, and four side walls rising up from side rims of the bottom wall. 
     The opening has a rectangular shape having a width dimension in an X direction longer than a width dimension in a Y direction perpendicular to the x direction. The energy storage element  3  is housed and a nonaqueous electrolyte is injected inside the case body  21 . The energy storage element  3  is housed in the case body  21  such that a longitudinal direction of the case body  21  and a longitudinal direction of the energy storage element  3  are matched. As described below, the energy storage device  3  is formed by winding a positive electrode  4  and a negative electrode  5  around a winding axis U with a separator  6  interposed between the positive electrode  4  and the negative electrode  5  to be a substantially oval shape. In the negative electrode  5 , a negative composite layer non-forming part  51  is projected on an X1 direction side more than an end S 1  of the separator  6  on a negative electrode current collector side. In the positive electrode  4 , a positive composite layer non-forming part  41  is projected on an X2 direction side more than an end S 2  of the separator  6  on a positive electrode current collector side. 
     On the lid  22 , a positive electrode terminal  7 , a negative electrode terminal  8 , positive electrode current collectors  9 , negative electrode current collectors  10 , and an inlet  13  are provided. The lid  22  has a substantially rectangular shape as a whole, and has a substantially same shape as the opening. The lid  22  is joined with the case body  21  to seal the opening of the case body  21 . Note that the lid  22  can be made of a material such as aluminum, an aluminum alloy, or the like. An outer rim of the lid  22  and the opening of the case body  21  are designed to be engaged, and the outer case  2  can be formed by welding the engaged portion. 
     On an outer surface of the lid  22 , which is an upper surface thereof, the positive electrode terminal  7  and the negative electrode terminal  8  are disposed. Specifically, the positive electrode terminal  7  is disposed on the X2 direction side in the X direction (longitudinal direction) of the lid  22 , and the negative electrode terminal  8  is disposed on the X1 direction side in the X direction (longitudinal direction) of the lid  22 . 
     The lid  22  includes the inlet  13  that passes through the outer surface of the lid  22  and an inner surface of the lid  22 . Specifically, the inlet  13  is formed at a portion near substantially the center in the X direction of the lid  22  and near substantially the center in the Y direction of the lid  22 . In a step of injecting the electrolyte, the electrolyte is injected inside the outer case  2  via the inlet  13 . After the electrolyte is injected, the inlet  13  is sealed by a liquid stopper. 
     The two positive electrode current collectors  9  extending from a lower surface of the lid  5  to a lower direction are electrically connected to the positive electrode terminal  7 . 
     The positive electrode current collector  9  has a long and narrow shape that extends along the positive composite layer non-forming part  41  (the part where a positive electrode collector foil is exposed) of the positive electrode  4  to be described below. The two positive electrode current collectors  9  are disposed such that their plate surfaces are opposed. The positive electrode current collector  9  is formed of an electrical conductive material, and can be manufactured using, for example, an aluminum alloy plate or the like. 
     The positive composite layer non-forming part  41  is sandwiched by the positive electrode current collectors  9  as well as clips  11 , and electrically connected thereto as illustrated in  FIG. 2 . It is preferable that the clips  11  be formed of a material having substantially the same resistance value as that of the material of the positive electrode current collectors  9  and the positive composite layer non-forming part  41  to be connected thereto. For example, the clip  11  can be manufactured by using, for example, an aluminum alloy or the like. 
     The two negative electrode current collectors  10  extending from the lower surface of the lid  5  to the lower direction are electrically connected to the negative electrode terminal  8 . 
     The negative electrode current collector  10  has a long and narrow shape that extends along the negative composite layer non-forming part  51  (part where a negative electrode collector foil is exposed) of the negative electrode  5  to be described below. The two negative electrode current collectors  10  are disposed such that their plate surfaces are opposed. The negative electrode current collector  10  is formed of an electrical conductive material, and can be manufactured using, for example, a copper alloy plate or the like. 
     The negative composite layer non-forming part  51  is sandwiched by the negative electrode current collectors  10  as well as clips  12 , and electrically connected thereto as illustrated in  FIG. 2 . It is preferable that the clips  12  be formed of a material having substantially the same resistance value as that of the material of the negative electrodes current collectors  10  and the negative composite layer non-forming part  51  to be connected thereto. The clip  12  can be manufactured by using, for example, a copper alloy or the like. 
     As illustrated in  FIG. 3  to  FIG. 6 , the positive electrode  4  includes the positive electrode current collector foil composed of an aluminum alloy foil, and positive composite layers  42  including a positive active material on surfaces of the positive electrode current collector foil. The positive active material is not specifically limited, and various positive active materials can be used. 
     The positive electrode  4  includes the positive composite layers  42  and the positive composite layer non-forming part  41  on the X2 direction side of the positive electrode current collector foil. The end of the positive composite layer  42  on the X1 direction (direction in which the negative composite layer non-forming part  51  projects) side is an end P 1  of the positive composite layer. The end of the positive composite layer  42  on the X2 direction (direction in which the positive composite layer non-forming part  41  projects) side is an end P 2  of the positive composite layer. A portion of the positive composite layer non-forming part  41  is projected on the X2 direction side from the end S 2  of the separator  6 . 
     The width of the positive electrode  4  in the Y direction is a thickness of the positive electrode  4 , and the thickness of the positive electrode  4  is “D” (see  FIG. 6 ). The width of the positive composite layer  42  in the Y direction is a thickness of the positive composite layer  42 , and the thickness of the positive composite layer  42  is “d” (see  FIG. 6 ). 
     As illustrated in  FIG. 3  to  FIG. 6 , the negative electrode  5  includes the negative electrode collector foil formed of a copper alloy foil and negative composite layers  52  including a negative active material on surfaces of the negative electrode collector foil. The negative active material is not specifically limited, and various negative active materials can be used. 
     The negative electrode  5  includes the negative composite layers  52  and the negative composite layer non-forming part  51  on the X1 direction side of the negative electrode collector foil. Furthermore, a portion of the negative composite layer non-forming part  51  is projected on the X1 direction side from the end S 1  of the separator  6 . 
     In the X direction, the width of the negative composite layer  52  is larger than the width of the positive composite layer  42 . The both ends in the X direction of the negative composite layer  52  is formed to extend on outer sides more than the both ends in the X direction of the positive composite layer  42 . 
     The separator  6  is disposed between the positive electrode  4  and the negative electrode  5 . In the X direction, the width of the separator  6  is larger than the width of the positive composite layer  42  and the width of the negative composite layer  52 . The both ends in the X direction of the separator  6  are formed to extend on the outer sides more than the both ends in the X direction of the positive composite layer  42  and the negative composite layer  52 . 
     The end on the X1 direction (the direction in which the negative composite layer non-forming part  51  projects) side of the separator  6  is the end S 1  of the separator  6 . The end S 1  of the separator  6  is disposed to project on the outer side more than the ends in the X1 direction of respective the positive composite layer  42  and the negative composite layer  52  in the X1 direction. 
     The end on the X2 direction (direction in which the positive composite layer non-forming part  41  projects) side of the separator  6  is the end S 2  of the separator  6 . The end S 2  of the separator  6  is disposed to project on the outer side more than the ends in the X2 direction of respective the positive composite layer  42  and the negative composite layer  52 . 
     The distance from the end P 1  of the positive composite layer  42  to the end S 1  of the separator  6  is W 1 . The distance from the end P 2  of the positive composite layer  42  to the end S 2  of the separator  6  is W 2 . 
     In the separator  6 , as illustrated in  FIG. 4 , an insulating layer  62  is formed on a surface, which is opposed to the positive electrode  4 , of a substrate  61  such as a microporous membrane, a non-woven fabric, or the like having insulation properties. Furthermore,  FIG. 4  illustrates a mode in which the positive electrode  4  and the negative electrode  5  are disposed with a constant distance with the separator  6  interposed therebetween. Note that the insulating layer  62  of the separator  6  is abbreviated in  FIG. 3 . 
     The substrate  61  of the separator  6  is not specifically limited as long as having insulating properties. A microporous membrane, a non-woven fabric, or the like can be used as the substrate  61 , and a material forming the substrate  61  includes, for example, polyolefin resin such as polyethylene, polypropylene, or the like. These materials may be used independently, or may be used by combining two or more of the materials. 
     The insulating layer  62  formed on the surface of the substrate  61  opposing the positive electrode  4  can be formed by applying a slurry for forming an insulating layer including inorganic particles, a binder, and a solvent and drying it. 
     The binder used for forming the insulating layer  62  is not specifically limited as far as it plays roles of biding inorganic particles to each other and biding inorganic particles and the substrate  61 . As the binder, for example, a solvent-based binder such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); an aqueous binder such as styrene-butadiene rubber (SBR) or a polyvinyl alcohol (PVA), or the like can be used. These binders may be independently used, or may be used by combining not less than two of them. The solvent-based binder denotes a binder that is used by being dissolved or dispersed in an organic solvent such as N-methylpyrrolidone (NMP). The aqueous binder denotes a binder that is used by being dissolved or dispersed in a solvent whose main component is water. 
     The inorganic particles used for the insulating layer  62  is not specifically limited, and for example, oxide-based ceramics such as silica, alumina, boehmite, titania, zirconia, magnesia, yttria, or zinc oxide; nitride-based ceramics such as silicon nitride, titanium nitride, or boron nitride; ceramics such as silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, kaolin clay, kaolinite, or calcium silicate; a glass fiber, or the like can be used. These inorganic particles may be independently used, or may be used by combining not less than two of them. 
     The average particle size (D50) of the inorganic particles is not specifically limited as far as they can be dispersed by a binder to be bound at a predetermined site. The average particle size (D50) of the inorganic particles is preferably not more than 20 μm, more preferably not more than 10 μm, and still more preferably not more than 5 μm. Also, the average particle size (D50) of the inorganic particles is preferably not less than 0.01 μm, more preferably not less than 0.1 μm, and still more preferably not less than 0.5 μm. 
     Alternatively, a plurality of inorganic particles different in their average particle sizes (D50) may be included in the insulating layer  62 . In this case, the average particle size (D50) of the largest inorganic particles is preferably not less than 1 μm and not more than 20 μm, and the average particle size (D50) of the smallest inorganic particles is preferably not less than 0.01 μm and less than 1 μm. This generates an appropriate gap between the positive composite layer  42  and the insulating layer  62 , which readily causes the electrolyte to penetrate into the positive composite layer, making it possible to further shorten the manufacturing time of the energy storage device, which is preferable. 
     Note that the average particle size (D50) of the inorganic particles can be measured by using a laser diffraction particle size analyzer (name of the analyzer: SALD-2200 (Shimadzu Corporation), measuring control software is Wing SALD-2200). 
     The porosity of the insulating layer  62  is not specifically limited and can be appropriately set. When the porosity of the insulating layer  62  is set not less than 40%, the electrolyte may be likely to be absorbed and held in the insulating layer  62 . By setting the porosity of the insulating layer  62  to be not less than 40%, as described below, since the possibility that the electrolyte is not efficiently supplied to the positive composite layer  42  becomes high, availability of applying the present invention may improve. That is, the porosity in the insulating layer  62  is preferably not less than 40%, more preferably not less than 50%, and still more preferably not less than 60%. 
     The content of the inorganic particles in the insulating layer  62  is not specifically limited, and can be appropriately set. The content of the inorganic particles is preferably not more than 99.9 wt. %, more preferably not more than 99 wt. %, and still more preferably not more than 98 wt. %, and still more preferably not more than 95 wt. % with respect to the total amount of the inorganic particles and the binder. Also, the content of the inorganic particles is preferably not less than 50 wt. %, more preferably not less than 80 wt. %, and still more preferably not less than 90 wt. % with respect to the total amount of the inorganic particles and the binder. 
     As compared with the energy storage device including a separator composed of only a substrate, in the energy storage device including the separator  6  in which the insulating layer  62  is formed on the surface of the substrate  61 , even when the energy storage device is used under a condition that is not normally foreseen, for example, even when abnormal heat generation occurs in the energy storage device, the separator  6  is less likely to be heat shrunk, so that electrical contact between the positive electrode and the negative electrode can be suppressed. 
     The electrolyte is not specifically limited as long as it is a liquid like state, and can include a supporting salt or a solvent. Viscosity of the electrolyte is not specifically limited, and can be appropriately set. Making the viscosity of the electrolyte under a circumstance of 25° C. be not more than 10 mPa*sec may cause the electrolyte to efficiently penetrate into the positive composite layer. That is, the viscosity of the electrolyte under a circumstance of 25° C. is preferably not more than 10 mPa*sec, more preferably not more than 5 mPa*sec, and still more preferably not more than 3.5 mPa*sec. 
     As the supporting salt, a supporting electrolyte typically used for a nonaqueous electrolyte battery can be employed. The supporting salt includes, for example, LiBF 4 , LiPF 6 , LiClO 4 , LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , LiN(CF 3 SO 2 )(C 4 F 9 SO 2 ), LiC(CF 3 SO 2 ) 3 , LiB(C 2 O 4 ) 2 , LiC(C 2 F 5 SO 2 ) 3 , or the like, and one of the compounds or a combination of not less than two selected from the compounds can be used. 
     As the solvent, a solvent typically used in a nonaqueous electrolyte battery can be employed. The solvent includes, for example, propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), or the like, and one of the compounds or a combination of not less than two selected from the compounds can be used. 
     In the processing for injecting the electrolyte, the electrolyte is injected inside the outer case  2  via the inlet  13 . The injected electrolyte may be, for example, accumulated on the bottom wall of the case body  21  composing the outer case  2  to be introduced on both ends in the X direction of the energy storage element  3  (a portion at which the positive composite layer non-forming part  41  is overlapped, and a portion at which the negative composite layer non-forming part  51  is overlapped), or may travel an outer surface of the energy storage element  3  to be introduced at the both ends in the X direction of the energy storage element  3 . 
     The electrolyte introduced to the both ends in the X direction of the energy storage element  3  penetrates toward near the center in the X direction of the composite layers (positive composite layer and the negative composite layer) from the both ends in the X direction of the composite layers. Specifically, the electrolyte introduced to the end in the X1 direction of the energy storage element  3  (the portion in which the negative composite layer non-forming part  51  is overlapped) penetrates toward the X2 direction from the ends in the X1 direction of respective the composite layers. Similarly, the electrolyte introduced to the end in the X2 direction of the energy storage element  3  (the portion in which the positive composite layer non-forming part  41  is overlapped) penetrates toward the X1 direction from the ends in the X2 direction of respective the composite layer. 
     The inventor of the present invention has found that, in the process in which the electrolyte penetrates into each of the composite layers, the process in which the electrolyte penetrates into the positive composite layer  42  takes more time as compared with the process in which the electrolyte penetrates into the negative composite layer  52 . That is, in order to shorten the manufacturing time of the energy storage device  1 , it may be effective to cause the electrolyte to efficiently penetrate into the positive composite layer  42 . 
     A cause of taking more time in the process in which the electrolyte penetrates into the positive composite layer  42  as compared with the process in which the electrolyte penetrates into the negative composite layer  52  may be that the insulating layer  62  of the separator  6  absorbs and holds more electrolyte to have a high liquid retaining property as compared with the substrate  61  of the separator  6 . The inorganic particles included in the insulating layer  62  may have a good affinity with the electrolyte, so that the insulating layer  62  of the separator  6  may have a high liquid retaining property of the electrolyte as compared with the substrate  61  of the separator  6 . 
     As illustrated in  FIG. 4  and  FIG. 5 , the positive electrode  4  is sandwiched by the insulating layers  62  of the separators  6  in the Y direction, and the negative electrode  5  is sandwiched by the substrates  61  of the separators  6  in the Y direction. 
     Herein, the process is examined in which the electrolyte penetrates into each of the composite layers from the end in the X1 direction of the energy storage element  3  (the portion in which the negative composite layer non-forming part  51  is overlapped). 
     In the process in which the electrolyte penetrates into the positive composite layer  42  from the X1 direction, the space in which the insulating layers  62  of the separators  6  are opposed becomes a route that introduces the electrolyte to the end P 1  of the positive composite layer  42 . After the electrolyte reaches the end P 1  of the positive composite layer  42 , the electrolyte sequentially penetrates into the positive composite layer  42 . 
     In the process of reaching the end P 1  of the positive composite layer  42  from the end in the X1 direction of the energy storage element  3 , some of the electrolyte may be absorbed and held in the insulating layer  62  having a relatively high liquid retaining property. That is, not all the electrolyte that travels the space in which the insulating layers  62  of the separators  6  are opposed to each other may be introduced to the end P 1  of the positive composite layer  42 , so that the electrolyte may not be efficiently supplied to the end P 1  of the positive composite layer  42 . 
     In the process in which the electrolyte penetrates into the negative composite layer  52  from the X1 direction, the space in which the substrate  61  of the separator  6  and the negative electrode collector foil (negative composite layer non-forming part  51 ) are opposed becomes a route that introduces the electrolyte to the end in the X1 direction of the negative composite layer  52 . After the electrolyte reaches the end in the X1 direction of the negative composite layer  52 , the electrolyte sequentially penetrates into the negative composite layer  52 . 
     In the process of reaching the end in the X1 direction of the negative composite layer  52  from the end in the X1 direction of the energy storage element  3 , that the electrolyte is absorbed and held in the substrate  61  and the negative electrode collector foil may rarely occur. That is, almost no electrolyte that travels in the space in which the substrate  61  of the separator  6  and the negative electrode collector foil are opposed may be absorbed in the substrate  61  and the negative electrode collector foil and almost all the electrolyte may be introduced to the end in the X1 direction of the negative composite layer  52 , so that the electrolyte may be efficiently supplied to the end in the X1 direction of the negative composite layer  52 . 
     Accordingly, when the process is examined in which the electrolyte penetrates into each of the composite layers from the end in the X1 direction of the energy storage element  3 , in the positive composite layer  42  sandwiched by the insulating layers  62  in the Y direction, some of the electrolyte may be readily absorbed and held by the insulating layers  62  as compared with the negative composite layer  52  sandwiched by the substrates  61  in the Y direction. This may make the electrolyte be not efficiently supplied to the end P 1  of the positive composite layer  42 , so that the process in which the electrolyte penetrates into the positive composite layer  42  may require more time as compared with the process in which the electrolyte penetrates into the negative composite layer  52  sandwiched by the substrates  61  in the Y direction. This may be because the insulating layer  62  absorbs and holds more electrolyte as compared with the substrate  61  and the negative electrode collector foil, so that it has a high liquid retaining property. 
     Note that the negative electrode collector foil (negative composite layer non-forming part  51 ) may have a property of absorbing a small amount of the electrolyte and hardly absorb the electrolyte like the substrate  61  of the separator  6 . 
     Herein, the process is examined in which the electrolyte penetrates into each of the composite layers from the end in the X2 direction of the energy storage element  3  (the portion in which the positive composite layer non-forming part  41  is overlapped). 
     In the process in which the electrolyte penetrates into the positive composite  42  from the X2 direction, the space in which the insulating layer  62  of the separator  6  and the positive electrode collector foil (positive composite layer non-forming part  41 ) are opposed becomes a route that introduces the electrolyte to the end P 2  of the positive composite layer  42 . After the electrolyte reaches the end in the X2 direction of the positive composite layer  42 , the electrolyte sequentially penetrates into the positive composite layer  42 . 
     In the process of reaching the end P 2  of the positive composite layer  42  from the end in the X2 direction of the energy storage element  3 , some of the electrolyte may be absorbed and held in the insulating layer  62  having a relatively high liquid retaining property. That is, not all the electrolyte that travels the space in which the insulating layer  62  of the separator  6  and the positive electrode collector foil (positive composite layer non-forming part  41 ) are opposed may be introduced to the end P 2  of the positive composite layer  42 , so that the electrolyte may not be efficiently supplied to the end P 2  of the positive composite layer  42 . 
     In the process in which the electrolyte penetrates into the negative composite layer  52  from the X2 direction, the space in which the substrates  61  of the separator  6  are opposed to each other becomes a route that introduces the electrolyte to the end in the X2 direction of the negative composite layer  52 . After the electrolyte reaches the end in the X2 direction of the negative composite layer  52 , the electrolyte sequentially penetrates into the negative composite layer  52 . 
     In the process of reaching the end in the X2 direction of the negative composite layer  52  from the end in the X2 direction of the energy storage element  3 , the electrolyte may be hardly absorbed and held in the substrate  61 . That is, the electrolyte that travels the space in which the substrates  61  of the separators  6  are opposed to each other may be hardly absorbed in the substrate  61 , and substantially all thereof may be introduced to the end in the X2 direction of the negative composite layer  52 , so that the electrolyte may be efficiently supplied to the end in the X2 direction of the negative composite layer  52 . 
     Therefore, when examining the process in which the electrolyte penetrates into each of the composite layers from the end in the X2 direction of the energy storage element  3 , in the positive composite layer  42  sandwiched between the insulating layers  62  in the Y direction, some of the electrolyte may be readily absorbed in the insulating layer  62  as compared with the negative composite layer  52  sandwiched between the substrates  61  in the Y direction. This prevents the electrolyte from being efficiently supplied to the end P 2  of the positive composite layer  42 , so that the process in which the electrolyte penetrates into the positive composite layer  42  may take more time as compared with the process in which the electrolyte penetrates into the negative composite layer  52  sandwiched between the substrates  61  in the Y direction. This may be because the insulating layer  62  absorbs and holds more electrolytes to have a high liquid retaining property as compared with the substrate  61  as described above. 
     Note that the positive electrode collector foil (positive composite layer non-forming part  41 ) may have a property of absorbing a small amount of the electrolyte and hardly absorb the electrolyte like the substrate  61  of the separator  6 . 
     According to the above description, when manufacturing the energy storage device  1  equipped with the separator  6  having the insulating layer  62  on its surface opposing the positive electrode  4 , in the process of injecting the electrolyte, the process in which the electrolyte penetrates into the positive composite layer  42  may take more time as compared with the process in which the electrolyte penetrates into the negative composite layer  52 . 
     Also, in order to increase the density of the positive composite layer  42  to increase the energy density of the energy storage device  1 , means of reducing the porosity of the positive composite layer  42  can be employed. When the porosity of the positive composite layer  42  is reduced, the electrolyte may become less likely to penetrate into the positive composite layer  42 , and the process in which the electrolyte penetrates into the positive composite layer  42  may take further more time. That is, in the energy storage device in which the porosity of the positive composite layer  42  is small, availability of the present invention that shortens the manufacturing time of the energy storage device may improve. 
     The porosity of the positive composite layer  42  is preferably not more than 40%, more preferably not more than 35%, and still more preferably not more than 30%. 
     Furthermore, when, for example, the process of injecting the electrolyte under a depressurized environment, unless the electrolyte penetrates into all the positive composite layer during the process of injecting the electrolyte, that is, during when the energy storage device in a state where the inlet  13  is not sealed by a liquid stopper is held under a depressurized environment, a portion exists in which the electrolyte is not penetrated into the positive composite layer of a completed energy storage device. The portion in which the electrolyte is not penetrated into the positive composite layer cannot contribute to charge-discharge reaction, which can result in lowering the capacity of the energy storage device. That is, applying the present invention may make it possible to reduce a disadvantage that the electrolyte is not fully penetrated into the positive composite layer to suppress lowering the capacity of the energy storage device. 
     The inventor of the present invention has found that the electrolyte can be efficiently penetrated into the positive composite layer  42  by defining a distance W 1  from the end P 1  of the positive composite layer  42  to the end S 1  of the separator  6 , and a distance W 2  from the end P 2  of the positive composite layer  42  to the end S 2  of the separator  6 , and has completed the present invention. 
     The electrolyte injected inside the outer case  2  reaches the ends (P 1  and P 2 ) in the X direction of the positive composite layer  42  from respective the ends in the X direction of the energy storage element  3 . Specifically, to the end P 1  of the positive composite layer  42 , the electrolyte travels in the space in which the insulating layers  62  are opposed to each other as a route. Similarly, to the end P 2  of the positive composite layer  42 , the electrolyte travels in the space in which the insulating layer  62  of the separator  6  and the positive electrode collector foil are opposed as a route. 
     That is, as described below, after the electrolyte is injected, unless the time to when the electrolyte reaches the end P 1  of the positive composite layer  42  and the time to when the electrolyte reaches the end P 2  of the positive composite layer  42  are deviated, the time of penetration of the electrolyte in the positive composite layer  42  may be shortened. 
     The time to when the electrolyte reaches the end P 1  of the positive composite layer  42  after the electrolyte is injected shall be T 1 . Similarly, the time to when the electrolyte reaches the end P 2  of the positive composite layer  42  after the electrolyte is injected shall be T 2 . 
     When there is no deviation between T 1  and T 2 , the electrolyte can start to penetrate into the positive composite layer  42  at substantially the same time from the end P 1  and the end P 2 . Therefore, when there is no deviation between T 1  and T 2 , when the electrolyte that penetrates into the X2 direction from the end P 1  and the electrolyte that penetrates into the X1 direction from the end P 2  penetrate to near substantially the center in the X direction of the positive composite layer  42 , the electrolyte penetrates to all the positive composite layer  42 . 
     Note that, the penetration velocity of the electrolyte into the positive composite layer  42  may be constant, and the magnitude of the velocity may also be same between when the electrolyte penetrates from the end P 1  to the X2 direction and when the electrolyte penetrates from the end P 2  to the X1 direction. 
     In contrast, when a deviation exists between T 1  and T 2 , one of the penetration of the electrolyte to the X2 direction from the P 1  or the penetration of the electrolyte from the end P 2  to the X1 direction starts first. Therefore, when a deviation exists between T 1  and T 2 , unless the electrolyte that penetrates into the X2 direction from the P 1  and the electrolyte that penetrates into the X1 direction from the end P 2  penetrate not to near substantially the center of the positive composite layer  42  in the X direction but to a portion deviated on the X1 direction side or the X2 direction side of the positive composite layer  42  in the X direction from respective the ends (the end P 1  and the end P 2 ), the electrolyte does not penetrate into all the positive composite layer  42 . That is, when a deviation exists between T 1  and T 2 , the electrolyte must penetrates to a far place deviated from near substantially the center of the positive composite layer  42  in the X direction from at least one of the ends (end P 1  or end P 2 ) of the positive composite layer  42  in the X direction (a portion deviated on the X1 direction side or the X2 direction side of the positive composite layer  42  in the X direction). 
     Furthermore, the penetration velocity of the electrolyte into the positive composite layer  42  may be slow as compared with the traveling velocity of the electrolyte to the end P 1  or the end P 2  of the positive composite layer  42  from the end S 1  or the end S 2  of the separator. This may be because the electrolyte sequentially penetrates into infinite holes existing in the positive composite layer  42  inside the positive composite layer  42 , whereas the electrolyte travels the space in which the insulating layers  62  are opposed to each other or the space in which the insulating layer  62  and the positive electrode collector foil are opposed as a route from the end S 1  or the end S 2  of the separator to the end P 1  or the end P 2  of the positive composite layer  42 . 
     According to the above description, when no deviation exists between T 1  and T 2 , a penetration time of the electrolyte into the positive composite layer  42  may be shortened as compared with the case where a deviation exists between T 1  and T 2 . 
     The inventor of the invention has tried to shorten the penetration time of the electrolyte into the positive composite layer  42  by defining the distance W 1  from the end P 1  of the positive composite layer  42  to the end S 1  of the separator  6  and the distance W 2  form the end P 2  of the positive composite layer  42  to the end S 2  of the separator  6  to reduce the deviation between T 1  and T 2 . 
     As illustrated in  FIG. 5  and  FIG. 6 , the space in which the insulating layers  62  of the separator  6  are opposed to each other that is a route for introducing the electrolyte to the end P 1  of the positive composite layer  42  has a wide extent as compared with the space in which the insulating layer  62  of the separator  6  and the positive electrode collector foil (positive composite layer non-forming part  41 ) are opposed that is a route for introducing the electrolyte to the end P 2  of the positive composite layer  42 . That is, when the distance W 1  and the distance W 2  are equal, the electrolyte that travels the space in which the insulating layers  62  of the separators  6  are opposed to each other may be efficiently introduced to the end (end P 1 ) of the positive composite layer  42  as compared with the electrolyte that travels the space in which the insulating layer  62  of the separator  6  and the positive electrode collector foil (positive composite layer non-forming part  41 ) are opposed. That is, defining the distance W 2  to be smaller than the distance W 1  may make it possible to reduce the deviation between T 1  and T 2 . The definitions of the distance W 1  and the distance W 2  can be estimated also by using the idea of plane Poiseuille flow as described below. As described above, the insulating layer  62  has a relatively high liquid retaining property of the electrolyte, so that the electrolyte may regularly penetrate into the insulating layer  62 , and the idea of the plane Poiseuille flow may be satisfied under such a condition. 
       FIG. 7  is a schematic diagram illustrating plane Poiseuille flow flowing through a space between two parallel slabs. Herein, the space between the two parallel slabs indicate a route formed by the insulating layers  62  of the separators  6  opposed to each other, or the route formed by the insulating layer  62  of the separator  6  and the positive electrode collector foil (positive composite layer non-forming part  41 ) that are opposed. In  FIG. 7 , the two slabs are parallel, and an x′ axis is defined along the center plane between the two slabs, and a y′ axis is defined in a direction perpendicular to the two slabs. 
       FIG. 7  is a schematic view of the electrolyte that travels between the two parallel slabs, and it is supposed that the traveling of the electrolyte is two dimensional steady flow, and has a velocity component only in one direction of the x′ direction. 
     Typically, when traveling of the fluid is the two dimensional steady flow, and has a velocity component of in only one direction, the relation between pressure gradient (dp/dx′) inside the fluid and second order differential (d 2 u/dy′ 2 ) of velocity is expressed by the following Formula (1).
 
 dp/dx ′=μ( d   2   u/dy′   2 )  Formula (1)
 
Herein, “p” denotes pressure in each point in the fluid, “u” denotes velocity (flow velocity) in each point in the fluid, and denotes viscosity coefficient of the fluid.
 
     When traveling of the fluid is two dimensional steady flow and has a velocity component only in one direction of x′ direction, the pressure gradient (dp/dx′) in the x′ direction is constant, and a velocity component u in the x′ direction can be expressed as u(y′). Since the pressure gradient (dp/dx′) in the x′ direction of the fluid is constant, Formula (2) is satisfied.
 
 dp/dx′=−a   Formula (2)
 
     Herein, “a” denotes a constant. 
     Formula (3) is derived from Formula (1) and Formula (2).
 
 d   2   u/dy′   2 =−( a /μ)  Formula (3)
 
     By integrating Formula (3) twice with respect to y′, Formula (4) is derived.
 
 u ( y ′)=−( ay′   2 /2)+ c   1   y′+c   2   Formula (4)
 
     Herein, c 1  and c 2  denote integral constants. 
     The flow velocity becomes 0 (u(±d′)=0) in the planes (y′=±d′) on which the fluid is in contact with the slabs. 
     By solving the two equations obtained by assigning the above-mentioned condition (u(±d′)=0 in y=±d′) to Formula (4) as simultaneous equations related to c 1  and c 2 , Formula (5) and Formula (6) are obtained.
 
 c   1 =0  Formula (5)
 
 c   2   =ad′   2 /2μ  Formula (6)
 
     By assigning Formula (5) and Formula (6) to Formula (4), the flow velocity u(y′) can be expressed by Formula (7).
 
 u ( y ′)=( ad′   2 /2μ)[1−( y/d ′) 2 ]  Formula(7)
 
     The volume that passes through any cross section perpendicular to the x′ axis shall be flow rate (volume flow rate) Q. Herein, when the width of the two slabs (length in the depth direction (direction perpendicular to the x′ axis and the y′ axis)) is ω, the flow rate Q can be obtained by integrating the flow velocity u(y′) from −d′ to d′ and multiplying it by the width ω as expressed by the following Formula (8). 
     
       
         
           
             
               
                 
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     The average flow velocity u ave  obtained by averaging the flow velocity u(y′) across between the two slabs y′=[−d′,d′] can be obtained by dividing the volume flow rate Q by 2dω as illustrated in the flowing Formula (9). 
     
       
         
           
             
               
                 
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                     ⁢ 
                     
                         
                     
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                     2 
                   
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     [Electrolyte that Travels the Route in which the Insulating Layers  62  of the Separators  6  are Opposed to Each Other] 
     As illustrated in  FIG. 6 , the insulating layers  62  of the separators  6  are substantially parallel to each other, and an x 1  axis is defined along the center surface between the insulating layers  62  of the separators  6  and a y 1  axis is defined in a direction perpendicular to the insulating layer  62  of the separator  6 . Traveling of the electrolyte that travels the route formed by the insulating layers  62  of the separators  6  opposed to each other may be two-dimensional steady flow depending on two components that are the x 1  direction and the y 1  direction, and may have a velocity component only in one direction of the x 1  direction. 
     On the surfaces (y 1 =±D/2) on which the electrode traveling the route formed by the insulating layers  62  of the separators  6  opposed to each other is in contact with the insulators  62  of the separators  6 , the flow velocity of the electrolyte becomes 0 (u(±D/2)=0). That is, the average flow velocity u ave(y1)  of the electrolyte traveling the route formed by the insulating layers  62  of the separators  6  opposed to each other can is obtained by averaging the flow velocity u(y1) across between the two slabs y1=[−D/2, D/2], so that it can be obtained by assigning d′ in Formula (9) to d′=D. Accordingly, the average flow velocity u ave(y1)  of the electrolyte travelling the route formed by the insulating layers  62  of the separators  6  opposed to each other is expressed by following Formula (10). In Formula (10), “a” denotes a constant, and “μ” denotes a viscosity coefficient of the electrolyte. 
     
       
         
           
             
               
                 
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     That is, the penetration of the electrolyte with respect to the positive composite layer  42  from the end P 1  progresses by supply of the electrolyte traveling at the average flow velocity u ave(y1)  to the route formed by the insulating layers  62  of the separators  6  opposed to each other. The electrolyte traveling at the average flow velocity u ave(y1)  may be supplied from the end P 1  to the positive composite layers  42  positioned in the respective Y1 and Y2 directions via the positive electrode collector foil. 
     [Electrolyte that Travels the Route in which the Insulating Layer  62  of the Separator  6  and the Positive Electrode Collector Foil are Opposed] 
     As illustrated in  FIG. 6 , the insulating layer  62  of the separator  6  and the positive electrode collector foil are substantially parallel. An X2 axis is defined along the center surface between the insulating layer  62  of the separator  6  and the positive electrode collector foil, and a y 2  axis is defined in a direction perpendicular to the insulating layer  62  of the separator  6  and the positive electrode collector foil. Traveling of the electrolyte that travels the route formed by the insulating layer  62  of the separator  6  and the positive electrode collector foil that are opposed may be two dimensional steady flow depending on two components that are the X2 direction and the y 2  direction, and may have a velocity component only in one direction of the x 2  direction. 
     On the surfaces (y1=±d/2) on which the electrolyte traveling the route formed by the insulating layer  62  of the separator  6  and the positive electrode collector foil is in contact with the insulating layer  62  of the separator  6  and the positive electrode collector foil, the flow velocity of the electrolyte becomes 0 (u(±d/2)=0). That is, the average flow velocity u ave(y2)  of the electrolyte traveling the path formed by the insulating layer  62  of the separator  6  and the positive electrode collector foil that are opposed is obtained by averaging the flow velocity u(y 2 ) across between the two slabs y 2 =[−d/2, d/2], so that it can be obtained by substituting d′=d to d′ in Formula 9. 
     Accordingly, the average flow velocity u ave(y2)  of the electrolyte that travels the path formed by the insulating layers  62  of the separators  6  that are opposed is expressed by following Formula 11. In formula 11, “a” denotes a constant, and “μ” denotes a viscosity coefficient of the electrolyte. 
     
       
         
           
             
               
                 
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     That is, the penetration of the electrolyte with respect to the positive composite layer  42  from the end P 2  progresses by supply of the electrolyte traveling at average flow velocity u ave(y2)  to the route formed by the insulating layer  62  of the separator  6  and the positive electrode collector foil that are opposed. 
     Comparing Formula (10) and Formula (11) shows that u ave(P1)  is larger than u ave(P2)  because the squared value of the thickness D of the positive electrode  4  is larger than the squared value of the thickness d of the positive composite layer  42 . 
     When the distance W 1  equals the distance W 2 , the length of the route formed by the insulating layers  62  of the separators  6  that are opposed to each other and the route formed by the insulating layer  62  of the separator  6  and the positive electrode collector foil (positive composite layer non-forming part  41 ) that are opposed become equal. 
     That is, when the distance W 1  and the distance W 2  are equal, in the process of injecting the electrolyte, the electrolyte that travels the route formed by the insulating layers  62  that are opposed reaches the end (end P 1 ) of the positive composite layer  42  earlier as compared with the electrolyte that travels the route formed by the insulating layer  62  and the positive electrode collector foil that are opposed depending on the magnitude relation of the average flow velocities, causing a deviation between T 1  and T 2 . Accordingly, in order to reduce the deviation between T 1  and T 2 , it is understood that it is effective to set the route formed by the insulating layer  62  and the positive electrode collector foil that are opposed shorter than the route formed by the insulating layers  62  that are opposed to each other. 
     The length of the route formed by the insulating layer  62  and the positive electrode collector foil that are opposed is W 1 , and the length of the route formed by the insulating layers  62  that are opposed to each other is W 2 , so that by satisfying the relation of W 1 &gt;W 2 , the penetration of the electrolyte into the positive electrode  4  is efficiently performed. That is, satisfying the relation of W 1 &gt;W 2  enables the electrolyte to efficiently penetrate into the positive electrode  4 , making it possible to shorten the manufacturing time of the energy storage device  1 . 
     Second Embodiment 
     In a second embodiment of the invention, 
     the thickness of the positive electrode is “D”, 
     the thickness of the positive composite layer is “d”, and 
     the distance W 2  is not less than 0.5(d 2 /D 2 )W 1  and not more than 2(d 2 /D 2 )W 1  in the energy storage device according to the first embodiment of the invention. 
     According to the above-mentioned second embodiment of the invention, in the injection process of the electrolyte, the electrolyte can be efficiently penetrated into the positive composite layer, so that the manufacturing time of the energy storage device can be shortened. 
     An energy storage device  100  according to the second embodiment will be described with reference to  FIG. 1  to  FIG. 7 . 
     In the second embodiment, the energy storage device  100  will be described in which the distance W 1  from the end P 1  of the positive composite layer  42  to the end S 1  of the separator  6 , and the distance W 2  from the end P 2  of the positive composite layer  42  to the end S 2  of the separator  6  are defined in a more preferable range. Furthermore, in the second embodiment, the same reference numerals are used for the same components as those in the first embodiment, and their description will be omitted. 
     As described above, the average flow velocity of the electrolyte supplied to the end P 1  and the average flow velocity of the electrolyte supplied to the end P 2  are respectively expressed by Formula (10) and Formula (11). That is, by adjusting the distance W 1  and the distance W 2  on the basis of the magnitudes of the average flow velocities of the electrolyte that travels respective the routes, the deviation between T 1  and T 2  can be reduced to cause the electrolyte to efficiently penetrate into the positive electrode  4 . 
     Formula (10) and Formula (11) shows that the average flow velocity u ave(P2)  of the electrolyte supplied to the end P 2  is d 2 /D 2  times of the average flow velocity u ave(P1)  of the electrolyte supplied to the end P 1 . Herein, as is apparent from  FIG. 4  to  FIG. 6 , it is understood that the thickness D of the positive electrode  4  is larger than the value obtained by multiplying two by the thickness d of the positive composite layer  42 , so that the value of d 2 /D 2  becomes less than ¼ in the first embodiment and the second embodiment of the invention. 
     That is, when the distance W 1  and the distance W 2  are equal, the average flow velocity u ave(P2)  of the electrolyte supplied to the end P 2  is d 2 /D 2  times, which is less than ¼, of the average flow velocity u ave(P1)  of the electrolyte supplied to the end P 1 , so that unless the electrolyte that penetrates from the ends (end P 1  and end P 2 ) penetrates to a portion deviated on the X2 direction side of the positive composite layer  42 , the electrolyte does not penetrate into all the positive composite layer  42 . 
     Thus, defining the distance W 2  to be not less than 0.5(d 2 /D 2 )W 1  and not more than 2(d 2 /D 2 )W 1  may make it possible to suppress generation of a large deviation between T 1  and T 2 . This makes the penetration toward the X2 direction from the end P 1  of the positive composite layer  42  and the penetration toward the X1 direction from the end P 2  of the positive composite layer  42  start without causing a large time deviation, so that the electrolyte penetrates into the positive electrode  4  more efficiently to shorten manufacturing time of the energy storage device  100 . 
     Also, when the distance W 2  is defined to be (d 2 /D 2 )W 1 , the penetration toward the X2 direction from the end P 1  of the positive composite layer  42 , and the penetration toward the X1 direction from the end P 2  of the positive composite layer  42  starts at substantially the same time, which may make the manufacturing time of the energy storage device  100  be shortest. That is, the distance W 2  is preferably not less than 0.5(d 2 /D 2 )W 1  and not more than 2(d 2 /D 2 )W 1 , more preferably not less than 0.7(d 2 /D 2 )W 1  and not more than 1.5(d 2 /D 2 )W 1 , and still more preferably not less than 0.8(d 2 /D 2 )W 1  and not more than 1.2(d 2 /D 2 )W 1 . 
     Third Embodiment 
     An energy storage device  100  according to a third embodiment will be described with reference to  FIG. 8 . In the third embodiment, the same reference numerals are used for the same components as those in the first embodiment or the second embodiment, and their description will be omitted. 
     The third embodiment of the invention has a tapering part in which the thickness of the positive composite layer  42  is reduced toward the X2 direction at the end P 2  of the positive composite layer  42 , in the first embodiment and the second embodiment. Herein, the tapering part is a part whose thickness transitions in a decreased manner in the X2 direction from a point of the positive composite layer  42 , and the point shall be a tapering start point Q. 
     The tapering part generates a flow of the electrolyte along the tapering part, facilitating penetration of the electrolyte to the space between the insulating layer  62  and the positive composite layer  42 . This enables the electrolyte to penetrate into the positive composite layer more efficiently, making it possible to reduce manufacturing time of the energy storage device. 
     The thickness change of the tapering part is preferably gentle. Specifically, given that the thickness of the composite layer  42  at the tapering start point Q is a reference, a distance Z between the tapering start point Q and a pint A at which the thickness of the positive composite layer is reduced by half (becomes d/2) in the X2 direction is preferably not less than 50 μm. The distance Z is more preferably not less than 100 μm, and still more preferably not less than 200 μm. 
     Making the distance Z be not less than 50 μm makes the space between the positive composite layer  42  of the tapering part and the insulating layer  62  become sufficiently larger than pores of the positive composite layer, and makes the volume of the space be moderately reduced toward the tapering start point Q, which may make it possible to preferentially introduce the electrolyte solution in the space. This makes it possible to preferably cause the electrolyte to penetrate into the positive composite layer more efficiently to shorten the manufacturing time of the energy storage device. 
     Note that the upper limit of the distance X may be in any range as long as it satisfies W 1 &gt;W 2  of the first embodiment or 0.5(d 2 /D 2 )W 1 ≤W 2 ≤2(d 2 /D 2 )W 1  of the second embodiment. 
     In the third embodiment, a covering layer having an electric resistance higher than that of the positive composite layer  42  may be included in the X2 direction of the positive composite layer  42 . Inclusion of the covering layer is preferable because the safeness of the energy storage device can be enhanced. 
     Note that, the covering layer is handled as being included in a part of the positive composite layer  42  in the third embodiment. 
     Other Embodiments 
     The technique disclosed in the description is not limited to the embodiments described above with reference to the drawings, and for example, the following various embodiments are also included therein. 
     In the above embodiments, examples are described in which the energy storage devices  1  and  100  are a lithium ion battery. However, this is not limited thereto, and the energy storage devices  1  and  100  may be another secondary battery such as a nickel hydrogen battery, or may be a primary battery. Alternatively, the energy storage devices  1  and  100  may be a capacitor or the like. 
     In the above-mentioned embodiments, the energy storage element  3  of the energy storage device  1  shall be the energy storage element  3  of a winding type formed into a flat shape by laminating and winding the positive electrode  4  and the negative electrode  5  with the separator  6  interposed therebetween, but this is not limited thereto. The energy storage element  3  may be a cylindrical energy storage element formed in a circular shape by laminating and winding them. The energy storage element  3  may be a laminated type energy storage element formed by laminating the positive electrode  4  and the negative electrode  5  with the separator  6  interposed therebetween. In the above-mentioned embodiments, the energy storage device  1  has one energy storage element  3 , but this is not limited thereto and the energy storage device  1  may include a plurality of the energy storage elements  3 . 
     Also, the invention can be provided as an energy storage apparatus including a plurality of the above-mentioned energy storage devices. An embodiment of the energy storage apparatus is illustrated in  FIG. 8 . In  FIG. 8 , an energy storage apparatus  1111  include a plurality of energy storage units  111 . Each of the energy storage units  111  includes a plurality of the energy storage devices  1  or  100 . The energy storage apparatus  1111  can be mounted as a power source for a vehicle such as an electric vehicle (EV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV). 
     INDUSTRIAL APPLICABILITY 
     The invention enables to shorten the manufacturing time of the energy storage device equipped with the separator including the insulating layer on its surface opposing the positive electrode. The invention can be effectively used for a power source for a vehicle, a power source for an electronic apparatus, a power source for power storage, or the like. 
     DESCRIPTION OF REFERENCE SIGNS 
     
         
         
           
               1 ,  100 : energy storage device 
               13 : inlet 
               111 : energy storage unit 
               1111 : energy storage apparatus 
               2 : outer case 
               21 : case body 
               22 : lid 
               3 : energy storage element 
               4 : positive electrode 
               41 : positive composite layer non-forming part 
               42 : positive composite layer 
               5 : negative electrode 
               51 : negative composite layer non-forming part 
               52 : negative composite layer 
               6 : separator 
               61 : substrate 
               62 : insulating layer 
               7 : positive electrode terminal 
               8 : negative electrode terminal 
               9 : positive electrode current collector 
               10 : negative electrode current collector 
               11 : clip for positive electrode 
               12 : clip for negative electrode