Patent Publication Number: US-2021175512-A1

Title: Lithium-ion rechargeable battery

Description:
TECHNICAL FIELD 
     The present invention relates to a lithium-ion rechargeable battery. 
     BACKGROUND ART 
     With widespread use of portable electronics, such as mobile phones and laptop computers, a strong need exists for small and lightweight rechargeable batteries with a high energy density. Known examples of the rechargeable batteries meeting such a need include lithium-ion rechargeable batteries. The lithium-ion rechargeable battery includes a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and an electrolyte having lithium ion conductivity and disposed between the positive electrode and the negative electrode. 
     Conventional lithium-ion rechargeable batteries have used an organic electrolyte solution and the like as an electrolyte. Meanwhile, use has been proposed of a solid electrolyte made of an inorganic material (inorganic solid electrolyte) as an electrolyte, and it has also been proposed to dispose a block region containing a positive electrode active material in a negative electrode collector on the negative electrode side; the block region helps prevent lithium from diffusing in the negative electrode collector (see Patent Document 1). 
     CITATION LIST 
     Patent Literature 
     Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2013-164971 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, even when a block region containing a positive electrode active material is disposed in a negative electrode collector, there have been cases where lithium passes through the block region to leak outside of the lithium-ion rechargeable battery. 
     An object of the present invention is to prevent lithium from leaking outside of an all-solid lithium-ion rechargeable battery. 
     Solution to Problem 
     According to a first aspect of the present invention, there is provided a lithium-ion rechargeable battery including, in the following order: a solid electrolyte layer containing an inorganic solid electrolyte having lithium ion conductivity; a storage layer configured to store lithium; and an amorphous metal layer made of a metal or an alloy and having an amorphous structure. 
     In the above lithium-ion rechargeable battery, the amorphous metal layer may contain chromium (Cr). 
     The amorphous metal layer may be made of an alloy of chromium (Cr) and titanium (Ti). 
     The amorphous metal layer may be made of a metal or an alloy that does not form an intermetallic compound with lithium. 
     The amorphous metal layer may be made of any one of ZrCuAlNiPdP, CuZr, FeZr, TiZr, CoZrNb, NiNb, NiTiNb, NiP, CuP, NiPCu, NiTi, CrTi, AlTi, FeSiB, and AuSi. 
     The storage layer may be made of a platinum group element (Ru, Rh, Pd, Os, Ir, or Pt) having a porous structure, gold (Au) having a porous structure, or an alloy of some of the platinum group elements or at least one of the platinum group elements and the gold having a porous structure. 
     The storage layer may be made of titanium having a plurality of columnar crystals each extending in a thickness direction. 
     The storage layer may contain a negative electrode active material. 
     The storage layer may contain a positive electrode active material. 
     The above lithium-ion rechargeable battery may further include a positive electrode layer on an opposite side of the solid electrolyte layer from the storage layer, the positive electrode layer containing a positive electrode active material. A plane size of the storage layer may be larger than a plane size of the positive electrode layer. 
     The above lithium-ion rechargeable battery may further include a noble metal layer on the amorphous metal layer, the noble metal layer being made of a platinum group element (Ru, Rh, Pd, Os, Ir, or Pt), gold (Au), or an alloy of some of the platinum group elements or at least one of the platinum group elements and the gold. 
     Advantageous Effects of Invention 
     The present invention prevents or restrains lithium from leaking outside of an all-solid lithium-ion rechargeable battery. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a sectional structure of a lithium-ion rechargeable battery of a first embodiment. 
         FIG. 2  is a flowchart of a method for manufacturing the lithium-ion rechargeable battery of the first embodiment. 
         FIG. 3  shows a sectional structure of the lithium-ion rechargeable battery of the first embodiment after film deposition and before an initial charge. 
         FIGS. 4A to 4C  explain a procedure for producing a porous storage layer. 
         FIG. 5A  is a cross-sectional STEM picture of the lithium-ion rechargeable battery after the film deposition and before the initial charge. 
         FIG. 5B  is a cross-sectional STEM picture of the lithium-ion rechargeable battery after an initial discharge. 
         FIG. 6  shows a sectional structure of the lithium-ion rechargeable battery of a first modification of the first embodiment. 
         FIG. 7  shows a sectional structure of the lithium-ion rechargeable battery of a second modification of the first embodiment. 
         FIG. 8  shows a sectional structure of the lithium-ion rechargeable battery of a third modification of the first embodiment. 
         FIG. 9  shows a sectional structure of the lithium-ion rechargeable battery of a fourth modification of the first embodiment. 
         FIGS. 10A and 10B  each show a sectional structure of the lithium-ion rechargeable battery of the second embodiment. 
         FIG. 11  shows a sectional structure of the lithium-ion rechargeable battery of the third embodiment. 
         FIG. 12  shows a cross-sectional STEM picture of the lithium-ion rechargeable battery of another exemplary configuration in the first embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described in detail below with reference to the attached drawings. In the drawings as referred to in the below description, dimensions of each component, including size and thickness, may differ from actual ones. 
     First Embodiment 
     [Configuration of the Lithium-Ion Rechargeable Battery] 
       FIG. 1  shows a sectional structure of a lithium-ion rechargeable battery  1  of a first embodiment. As described later, the lithium-ion rechargeable battery  1  of the present embodiment has a multilayer structure composed of multiple layers (films); its basic structure is formed by a so-called deposition process, and the structure is completed by an initial charging and discharging operations.  FIG. 1  shows the lithium-ion rechargeable battery  1  after the initial discharging operation, namely after completion of its structure. 
     The lithium-ion rechargeable battery  1  shown in  FIG. 1  includes: a substrate  10 ; a positive electrode collector layer  20  stacked on the substrate  10 ; a positive electrode layer  30  stacked on the positive electrode collector layer  20 ; a solid electrolyte layer  40  stacked on the positive electrode layer  30 ; and a storage layer  50  stacked on the solid electrolyte layer  40 . The solid electrolyte layer  40  covers peripheries of both of the positive electrode collector layer  20  and the positive electrode layer  30 , and an end of the solid electrolyte layer  40  is directly stacked on the substrate  10 , whereby the solid electrolyte layer  40  covers the positive electrode collector layer  20  and the positive electrode layer  30  jointly with the substrate  10 . The lithium-ion rechargeable battery  1  further includes a coating layer  60  stacked on the storage layer  50  and also directly stacked on the solid electrolyte layer  40  around the periphery of the storage layer  50  to coat the storage layer  50  jointly with the solid electrolyte layer  40 . The lithium-ion rechargeable battery  1  further includes a negative electrode collector layer  70  stacked on the coating layer  60  and also directly stacked on the solid electrolyte layer  40  around the periphery of the coating layer  60  to cover the coating layer  60  jointly with the solid electrolyte layer  40 . 
     The above constituents of the lithium-ion rechargeable battery  1  will be described in more detail below. 
     (Substrate) 
     The substrate  10  is not limited to a particular material, and may be made of any of various materials including metal, glass, and ceramics. 
     In the present embodiment, the substrate  10  is composed of a metal plate having electronic conductivity. More specifically, in the present embodiment, stainless steel foil (plate), which has higher mechanical strength than copper, aluminum and the like, is used as the substrate  10 . Alternatively, metallic foil obtained by plating with conductive metals, such as tin, copper, chrome and the like, may be used as the substrate  10 . 
     The substrate  10  may have a thickness of 20 μm or more and 2000 μm or less, for example. A thickness of less than 20 μm may lead to insufficient strength of the lithium-ion rechargeable battery  1 . Meanwhile, a thickness of more than 2000 μm leads to reduced volume energy density and weight energy density due to increase in battery weight and thickness. 
     (Positive Electrode Collector Layer) 
     The positive electrode collector layer  20  may be a solid thin film having electronic conductivity. As long as these conditions are met, the positive electrode collector layer  20  is not limited to a particular material and may be made of, for example, any conductive material including various metals and alloys of metals. 
     The positive electrode collector layer  20  may have a thickness of 5 nm or more and 50 μm or less, for example. With a thickness of less than 5 nm, the positive electrode collector layer  20  has reduced current collection capability, which makes the lithium-ion rechargeable battery  1  impracticable. Meanwhile, when the positive electrode collector layer  20  has a thickness of more than 50 μm, it increases internal resistance of the battery, which is disadvantageous for high speed charging/discharging. 
     While any known deposition method may be used to manufacture the positive electrode collector layer  20 , such as various physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods, it is preferable to use a sputtering method or a vacuum deposition method in terms of production efficiency. 
     When the substrate  10  is made of a conductive material such as a metal plate, there is no need to provide the positive electrode collector layer  20  between the substrate  10  and the positive electrode layer  30 . When the substrate  10  is made of an insulating material, it is preferable to provide the positive electrode collector layer  20  between the substrate  10  and the positive electrode layer  30 . 
     (Positive Electrode Layer) 
     The positive electrode layer  30  is a solid thin film and contains a positive electrode active material that releases lithium ions during a charge and occludes lithium ions during a discharge. The positive electrode active material constituting the positive electrode layer  30  may be any of various materials such as oxides, sulfides or phosphorus oxides containing at least one kind of metals selected from manganese (Mn), cobalt (Co), nickel (Ni), iron (Fe), molybdenum (Mo), and vanadium (V). Alternatively, the positive electrode layer  30  may be made of a positive electrode mixture containing a solid electrolyte. 
     The positive electrode layer  30  may have a thickness of 10 nm or more and 40 μm or less, for example. With the positive electrode layer  30  having a thickness of less than 10 nm, the lithium-ion rechargeable battery  1  obtained therefrom has a too small capacity, which makes the lithium-ion rechargeable battery  1  impracticable. Meanwhile, with the positive electrode layer  30  having a thickness of more than 40 μm, it takes too much time to form the layer, which reduces productivity. The positive electrode layer  30  may, however, have a thickness of more than 40 μm when a large battery capacity is required of the lithium-ion rechargeable battery  1 . 
     While any known deposition method may be used to fabricate the positive electrode layer  30 , such as various PVD and CVD methods, it is preferable to use a sputtering method in terms of production efficiency. 
     (Solid Electrolyte Layer) 
     The solid electrolyte layer  40  is a solid thin film and contains a solid electrolyte made of an inorganic material (inorganic solid electrolyte). The inorganic solid electrolyte constituting the solid electrolyte layer  40  is not limited to a particular material as long as the inorganic solid electrolyte has lithium ion conductivity, and may be made of any of various materials including oxides, nitrides, and sulfides. 
     The solid electrolyte layer  40  may have a thickness of 10 nm or more and 10 μm or less, for example. With the solid electrolyte layer  40  having a thickness of less than 10 nm, the lithium-ion rechargeable battery  1  obtained therefrom is prone to a short circuit (leakage) between the positive electrode layer  30  and the storage layer  50 . Meanwhile, when the solid electrolyte layer  40  has a thickness of more than 10 μm, it increases internal resistance of the battery, which is disadvantageous for high speed charging/discharging. 
     While any known deposition method may be used to manufacture the solid electrolyte layer  40 , such as various PVD and CVD methods, it is preferable to use a sputtering method in terms of production efficiency. 
     (Storage Layer) 
     The storage layer  50  is a solid thin film and has a function to store lithium ions. 
     The storage layer  50  shown in  FIG. 1  includes a porous part  51  with a number of pores  52 . That is, the storage layer  50  of the present embodiment has a porous structure. This porous storage layer  50 , or the porous part  51 , is formed by initial charging and discharging operations after film deposition, which will be described in detail later. 
     The storage layer  50  (the porous part  51 ) may be made of a platinum group element (Ru, Rh, Pd, Os, Ir, Pt), gold (Au), or an alloy of some of these metals. Among these, the storage layer  50  is preferably composed of platinum (Pt) or gold (Au), which are less prone to oxidation. The storage layer  50  (the porous part  51 ) may be a polycrystal of any of the above noble metals or an alloy of some of these metals. 
     The storage layer  50  may have a thickness of 10 nm or more and 40 μm or less, for example. With a thickness of less than 10 nm, the storage layer  50  lacks sufficient capacity to store lithium. Meanwhile, when the storage layer  50  has a thickness of more than 40 μm, it increases internal resistance of the battery, which is disadvantageous for high speed charging/discharging. The storage layer  50  may, however, have a thickness of more than 40 μm when a large battery capacity is required of the lithium-ion rechargeable battery  1 . 
     While any known deposition method may be used to manufacture the storage layer  50 , such as various PVD and CVD methods, it is preferable to use a sputtering method in terms of production efficiency. Making the storage layer  50  porous is preferably done by charging and discharging, as described later. 
     (Coating Layer) 
     The coating layer  60 , which is an example of the amorphous metal layer, is a solid thin film made of any metal or alloy having an amorphous structure. Among these, in terms of corrosion resistance, the coating layer  60  is preferably made of a simple substance of chromium (Cr) or an alloy containing chromium, and more preferably made of an alloy of chromium and titanium (Ti). Also, the coating layer  60  is preferably made of any metal or alloy that does not form an intermetallic compound with lithium (Li). The coating layer  60  may also be composed of a stack of multiple amorphous layers made of different materials (e.g., a stack of an amorphous chromium layer and an amorphous chromium-titanium alloy layer). When the coating layer  60  is formed of an alloy, the range of composition ratio to produce an amorphous structure depends on layer forming conditions and thus a preferable range of composition ratio cannot be prescribed. The composition ratio may be selected depending on combination with layer forming conditions. 
     The term “amorphous structure” as referred to in the present embodiment not only means an entirely amorphous structure but also means an amorphous structure in which microcrystals are deposited. 
     The coating layer  60  may have a thickness of 10 nm or more and 40 μm or less, for example. With a thickness of less than 10 nm, the coating layer  60  may hardly block lithium having passed through the storage layer  50  from the solid electrolyte layer  40  side. Meanwhile, when the coating layer  60  has a thickness of more than 40 μm, it increases internal resistance of the battery, which is disadvantageous for high speed charging/discharging. 
     While any known deposition method may be used to manufacture the coating layer  60 , such as various PVD and CVD methods, it is preferable to use a sputtering method in terms of production efficiency. In particular, when the coating layer  60  is made of the above chromium-titanium alloy, use of a sputtering method facilitates amorphization of the chromium-titanium alloy. 
     Examples of metals (alloys) that can be used for the coating layer  60  include ZrCuAlNiPdP, CuZr, FeZr, TiZr, CoZrNb, NiNb, NiTiNb, NiP, CuP, NiPCu, NiTi, CrTi, AlTi, FeSiB, and AuSi. 
     (Negative Electrode Collector Layer) 
     The negative electrode collector layer  70 , which is an example of the noble metal layer, may be a solid thin film having electronic conductivity. As long as these conditions are met, the negative electrode collector layer  70  is not limited to a particular material and may be made of, for example, any conductive material including various metals and alloys of metals. In terms of preventing corrosion of the coating layer  60 , a chemically stable material is preferably used for the negative electrode collector layer  70 ; for example, the negative electrode collector layer  70  is preferably made of a platinum group element (Ru, Rh, Pd, Os, Ir, Pt), gold (Au), or an alloy of some of these metals. 
     The negative electrode collector layer  70  may have a thickness of 5 nm or more and 50 μm or less, for example. A thickness of less than 5 nm leads to reduced corrosion resistance and current collecting function of the negative electrode collector layer  70 , which makes the lithium-ion rechargeable battery  1  impracticable. Meanwhile, when the negative electrode collector layer  70  has a thickness of more than 50 μm, it increases internal resistance of the battery, which is disadvantageous for high speed charging/discharging. 
     While any known deposition method may be used to manufacture the negative electrode collector layer  70 , such as various PVD and CVD methods, it is preferable to use a sputtering method in terms of production efficiency. 
     (Relationship Between the Positive Electrode Layer and the Storage Layer) 
     In the lithium-ion rechargeable battery  1 , the positive electrode layer  30  and the storage layer  50  face each other across the solid electrolyte layer  40 . That is, the positive electrode layer  30  containing a positive electrode active material is positioned on the opposite side of the solid electrolyte layer  40  from the storage layer  50 . When viewed from above in  FIG. 1 , the plane size of the storage layer  50  is larger than that of the positive electrode layer  30 . Also, when viewed from above in  FIG. 1 , the entire periphery of the plane of the positive electrode layer  30  is positioned within the entire periphery of the plane of the storage layer  50 . Thus, a top face (plane) of the positive electrode layer  30  shown in  FIG. 1  is faced with a bottom face (plane) of the storage layer  50  across the solid electrolyte layer  40 . 
     [Method for Manufacturing the Lithium-Ion Rechargeable Battery] 
     Below a description will be given of a method for manufacturing the above lithium-ion rechargeable battery  1 . 
       FIG. 2  is a flowchart of a method for manufacturing the lithium-ion rechargeable battery  1  of the first embodiment. 
     First, a positive electrode collector layer forming step is performed where the substrate  10  is mounted on a sputtering device (not shown) and the positive electrode collector layer  20  is formed on the substrate  10  (step  20 ). Then, a positive electrode layer forming step is performed where the positive electrode layer  30  is formed on the positive electrode collector layer  20  by the sputtering device (step  30 ). Then, a solid electrolyte layer forming step is performed where the solid electrolyte layer  40  is formed on the positive electrode layer  30  by the sputtering device (step  40 ). A storage layer forming step is then performed where the storage layer  50  is formed on the solid electrolyte layer  40  by the sputtering device (step  50 ). A coating layer forming step is performed where the coating layer  60  is formed on the solid electrolyte layer  40  and the storage layer  50  by the sputtering device (step  60 ). Then, a negative electrode collector layer forming step is performed where the negative electrode collector layer  70  is formed on the solid electrolyte layer  40  and the coating layer  60  (step  70 ). Executing these steps  20  to  70  results in the lithium-ion rechargeable battery  1  after film deposition (and before an initial charge) as shown in  FIG. 3  described later. This lithium-ion rechargeable battery  1  is removed from the sputtering device. 
     Then, an initial charge step is performed where the lithium-ion rechargeable battery  1  removed from the sputtering device is given an initial charge (step  80 ). Subsequently, an initial discharge step is performed where the charge lithium-ion rechargeable battery  1  performs an initial discharge (step  90 ). Through these initial charge and discharge, the storage layer  50  becomes porous, or the porous part  51  and a number of pores  52  are formed, resulting in the lithium-ion rechargeable battery  1  shown in  FIG. 1 . The porous storage layer  50  produced by the initial charge and discharge will be detailed later. 
     [Configuration of the Lithium-Ion Rechargeable Battery after the Film Deposition and Before the Initial Charge] 
       FIG. 3  shows a sectional structure of the lithium-ion rechargeable battery  1  of the first embodiment after the film deposition and before the initial charge.  FIG. 3  shows the lithium-ion rechargeable battery  1  when steps  20  to  70  shown in  FIG. 2  have been completed.  FIG. 1  shows the lithium-ion rechargeable battery  1  after completion of step  90  (i.e. all steps) shown in  FIG. 2 . 
     The basic structure of the lithium-ion rechargeable battery  1  shown in  FIG. 3  is the same as that of the lithium-ion rechargeable battery  1  shown in  FIG. 1 , except that the storage layer  50  of the lithium-ion rechargeable battery  1  shown in  FIG. 3  is not porous but denser than the storage layer  50  shown in  FIG. 1 . Additionally, the lithium-ion rechargeable battery  1  shown in  FIG. 3  differs from the lithium-ion rechargeable battery  1  shown in  FIG. 1  in that the thickness of the storage layer  50  shown in  FIG. 3  is smaller than that of the storage layer  50  shown in  FIG. 1 . 
     [Production of the Porous Storage Layer] 
     Below a detailed description will be given of production of the above porous storage layer  50 . 
       FIGS. 4A to 4C  are enlarged views of the storage layer  50  and its nearby layers for explaining a procedure for producing the porous storage layer  50 .  FIG. 4A  shows the state after the film deposition and before the initial charge (i.e. after step  70 ),  FIG. 4B  shows the state after the initial charge and before the initial discharge (i.e. the state between step  80  and step  90 ), and  FIG. 4C  shows the state after the initial discharge (i.e. after step  90 ). Thus,  FIG. 4A  corresponds to  FIG. 3  and  FIG. 4C  corresponds to  FIG. 1 . 
     (After the Film Deposition and Before the Initial Charge) 
     In the state after the film deposition and before the initial charge shown in  FIG. 4A , the storage layer  50  is dense. The storage layer  50  has a storage layer thickness t 50 , the coating layer  60  has a coating layer thickness t 60 , and the negative electrode collector layer  70  has a negative electrode collector layer thickness t 70 . 
     (After the Initial Charge and Before the Initial Discharge) 
     When the lithium-ion rechargeable battery  1  shown in  FIG. 4A  is charged (initially charged), a positive electrode of a DC power source is connected to the substrate  10  (see  FIG. 1 ), and a negative electrode of the DC power source is connected to the negative electrode collector layer  70 . This causes lithium ions (Lit) constituting the positive electrode active material in the positive electrode layer  30  to move through the solid electrolyte layer  40  to the storage layer  50 . In other words, in the charging operation, lithium ions move in the thickness direction (in the upward direction in  FIG. 4B ) of the lithium-ion rechargeable battery  1 . 
     At this time, the lithium ions having moved from the positive electrode layer  30  to the storage layer  50  are alloyed with the noble metal constituting the storage layer  50 . For example, when the storage layer  50  is made of platinum (Pt), lithium is alloyed with platinum in the storage layer  50  (formation of a solid solution, formation of an intermetallic compound, or formation of a eutectic). 
     Also, some of lithium ions having entered the storage layer  50  pass therethrough to reach a boundary between the storage layer  50  and the coating layer  60 . The coating layer  60  of the present embodiment is made of a metal or alloy having an amorphous structure and thus includes the significantly smaller number of grain boundaries than the storage layer  50 , which has a polycrystalline structure. For this reason, the lithium ions having reached the boundary between the storage layer  50  and the coating layer  60  hardly enter the coating layer  60 , and they remain stored within the storage layer  50 . 
     After completion of the initial charge, the lithium ions having moved from the positive electrode layer  30  to the storage layer  50  are stored within the storage layer  50 . The reason why the lithium ions having moved to the storage layer  50  are stored within the storage layer  50  is likely to be because the lithium ions are alloyed with platinum or metallic lithium is deposited in platinum. 
     As shown in  FIG. 4B , after the initial charge and before the initial discharge of the lithium-ion rechargeable battery  1 , the storage layer thickness t 50  increases from its thickness after the film deposition and before the initial charge shown in  FIG. 4A . In other words, the volume of the storage layer  50  is increased by the initial charge. This is likely to be because of alloying of lithium and platinum in the storage layer  50 . On the other hand, the coating layer thickness t 60  changes little before and after the initial charge. In other words, the volume of the coating layer  60  is changed little by the initial charge. This is likely to be because lithium hardly enters the coating layer  60 . This assumption can be backed by the fact that the negative electrode collector layer thickness t 70  changes little before and after the initial charge, or in other words, the volume of the negative electrode collector layer  70  changes little before and after the initial charge (platinum constituting the negative electrode collector layer  70  is not made porous, unlike platinum constituting the storage layer  50 , and remains dense). 
     (After the Initial Discharge) 
     When the lithium-ion rechargeable battery  1  shown in  FIG. 4B  is discharged (initially discharged), a positive side of a load is connected to the substrate  10  (see  FIG. 1 ) and a negative side of the load is connected to the negative electrode collector layer  70 . This causes lithium ions (Lit) stored in the storage layer  50  to move through the solid electrolyte layer  40  to the positive electrode layer  30 , as shown in  FIG. 4C . In other words, in the discharging operation, lithium ions move in the thickness direction (the downward direction in  FIG. 4C ) of the lithium-ion rechargeable battery  1  to be stored in the positive electrode layer  30 . Along with this, a direct current is supplied to the load. 
     At this time, dealloying of the lithium-platinum alloy (when metal lithium is deposited in platinum, solubilization of metal lithium) takes place in the storage layer  50  as lithium leaves the storage layer  50 . As a result of the dealloying in the storage layer  50 , the storage layer  50  becomes porous, resulting in the porous part  51  with a number of pores  52 . The thus-obtained porous part  51  is composed almost entirely of a noble metal (e.g., platinum). After completion of the initial discharge, however, lithium does not disappear in the storage layer  50  but some lithium that does not move during the discharging operation remains in the storage layer  50 . 
     As shown in  FIG. 4C , after the initial discharge of the lithium-ion rechargeable battery  1 , the storage layer thickness t 50  decreases from its thickness after the initial charge and before the initial discharge shown in  FIG. 4B . This is likely to be because of the dealloying of the lithium-platinum alloy in the storage layer  50 . This assumption can be backed by the fact that the shape of each pore  52  formed in the storage layer  50  by the initial discharge is flattened such that its length in the thickness direction is shorter than its length in the plane direction. Also, as shown in  FIG. 4C , after the initial discharge of the lithium-ion rechargeable battery  1 , the storage layer thickness t 50  increases from its thickness after the film deposition and before the initial charge shown in  FIG. 4A . This is likely to be because the storage layer  50  is made porous, or a large number of pores  52  are formed in the storage layer  50 , by the initial charge and discharge. On the other hand, the coating layer thickness t 60  and the negative electrode collector layer thickness t 70  change little before and after the initial discharge. 
     [Exemplary Configuration of the Lithium-Ion Rechargeable Battery] 
       FIGS. 5A and 5B  are cross-sectional scanning transmission electron microscope (STEM) pictures of the lithium-ion rechargeable battery  1  of the present embodiment;  FIG. 5A  shows a STEM picture of the lithium-ion rechargeable battery  1  after the film deposition and before the initial charge, and  FIG. 5B  shows a STEM picture of the lithium-ion rechargeable battery  1  after the initial discharge. These STEM pictures were taken by Ultra-thin Film Evaluation System HD-2300 from Hitachi High-Technologies Corporation.  FIG. 5A  corresponds to  FIG. 4A  (and  FIG. 3 ), and  FIG. 5B  corresponds to  FIG. 4C  (and  FIG. 1 ). 
     The specific configuration and manufacturing method of the lithium-ion rechargeable battery  1  shown in  FIG. 5A  are as follows. 
     Stainless steel (SUS304) was used as the substrate  10  (omitted in  FIGS. 5A and 5B ). The substrate  10  was 30 μm thick. 
     Aluminum formed by sputtering was used as the positive electrode collector layer  20  (omitted in  FIGS. 5A and 5B ). The positive electrode collector layer  20  was 100 nm thick. 
     Lithium manganate (Li 1.5 Mn 2 O 4 ) formed by sputtering was used as the positive electrode layer  30  (omitted in  FIGS. 5A and 5B ). The positive electrode layer  30  was 1000 nm thick. 
     LiPON (obtained by displacing a part of oxygen in lithium phosphate (Li 3 PO 4 ) with nitrogen) formed by sputtering was used as the solid electrolyte layer  40 . The solid electrolyte layer  40  was 1000 nm thick. 
     Platinum (Pt) formed by sputtering was used as the storage layer  50 . The storage layer  50  was 410 nm thick (after the film deposition and before the initial charge). 
     Chromium-titanium alloy (more specifically, Cr 50 Ti 50 ) formed by sputtering was used as the coating layer  60 . The coating layer  60  was 50 nm thick. 
     Platinum (Pt) formed by sputtering was used as the negative electrode collector layer  70 . The negative electrode collector layer  70  was 100 nm thick. 
     The thus-obtained lithium-ion rechargeable battery  1  after the film deposition and before the initial charge (see  FIG. 3 ) was subjected to electron diffraction for analysis of its crystal structure. The results were as follows. 
     The substrate  10  made of SUS304, the positive electrode collector layer  20  made of aluminum, and the storage layer  50  and the negative electrode collector layer  70  made of platinum were crystalized. On the other hand, the positive electrode layer  30  made of lithium manganate, the solid electrolyte layer  40  made of LiPON, and the coating layer  60  made of chromium-titanium alloy were amorphous. However, rings were slightly observed in the electron diffraction patterns of the positive electrode layer  30 , the solid electrolyte layer  40 , and the coating layer  60 ; they were found to contain microcrystals in the amorphous structure. 
     The thus-obtained lithium-ion rechargeable battery  1  was subjected to the initial charge and the initial discharge. 
     Initial Charge Conditions 
     Current: 1C 
     End voltage: 4.0V or 2 hours 
     Initial Discharge Conditions 
     Current: 1C 
     End voltage: 2.0V 
     The STEM pictures shown in  FIGS. 5A and 5B  will be described below. 
     In  FIG. 5A , the storage layer  50  is almost uniformly white, whereas in  FIG. 5B , multiple gray spots are present on the white background. In  FIG. 5B , some gray spots in the storage layer  50  near the boundary between the storage layer  50  and the coating layer  60  are flattened with a shorter length in the thickness direction than a length in the plane direction and are relatively larger than other gray spots in the storage layer  50 . In  FIG. 5B , the white background portion is considered as corresponding to the porous part  51 , and the gray portions are considered as corresponding to the pores  52 . In  FIG. 5B , the storage layer  50  is thicker than the storage layer  50  shown in  FIG. 5A . The storage layer  50  shown in  FIG. 5B  was 610 nm thick (after the initial discharge). 
     Both of the coating layer  60  and the negative electrode collector layer  70  have little change in gray level between the pictures of  FIGS. 5A and 5B . Further, both of the coating layer  60  and the negative electrode collector layer  70  have little change in thickness between the pictures of  FIGS. 5A and 5B . 
     [Another Exemplary Configuration of the Lithium-Ion Rechargeable Battery] 
       FIG. 12  shows a cross-sectional STEM picture of the lithium-ion rechargeable battery  1  of another exemplary configuration in the present embodiment.  FIG. 12  shows the lithium-ion rechargeable battery  1  after the initial discharge. This picture was taken by Ultra-thin Film Evaluation System HD-2300 from Hitachi High-Technologies Corporation, similarly to the above pictures of  FIGS. 5A and 5B .  FIG. 12  corresponds to  FIG. 4C  (and  FIG. 1 ) described above. 
     The specific configuration and manufacturing method of the lithium-ion rechargeable battery  1  shown in  FIG. 12  are as follows. 
     Stainless steel (SUS304) was used as the substrate  10  (omitted in  FIG. 12 ). The substrate  10  was 30 μm thick. 
     Aluminum formed by sputtering was used as the positive electrode collector layer  20  (omitted in  FIG. 12 ). The positive electrode collector layer  20  was 100 nm thick. 
     Lithium manganate (Li 1.5 Mn 2 O 4 ) formed by sputtering was used as the positive electrode layer  30  (omitted in  FIG. 12 ). The positive electrode layer  30  was 1000 nm thick. 
     Lithium phosphate (Li 3 PO 4 ) formed by sputtering was used as the solid electrolyte layer  40 . The solid electrolyte layer  40  was 1000 nm thick. 
     Platinum (Pt) formed by sputtering was used as the storage layer  50 . The storage layer  50  was 70 nm thick (after the film deposition and before the initial charge). 
     CoZrNb alloy (more specifically, Co 91 Zr 5 Nb 4 ) formed by sputtering was used as the coating layer  60 . The coating layer  60  was 200 nm thick. 
     Platinum (Pt) formed by sputtering was used as the negative electrode collector layer  70 . The negative electrode collector layer  70  was 70 nm thick. 
     The thus-obtained lithium-ion rechargeable battery  1  after the film deposition and before the initial charge was subjected to electron diffraction for analysis of its crystal structure. The results were as follows. 
     The substrate  10  made of SUS304, the positive electrode collector layer  20  made of aluminum, and the storage layer  50  and the negative electrode collector layer  70  made of platinum were crystalized. On the other hand, the positive electrode layer  30  made of lithium manganate, the solid electrolyte layer  40  made of lithium phosphate (Li 3 PO 4 ), and the coating layer  60  made of CoZrNb alloy were amorphous. However, rings were slightly observed in the electron diffraction patterns of the positive electrode layer  30 , the solid electrolyte layer  40 , and the coating layer  60 ; they were found to contain microcrystals in the amorphous structure. 
     The thus-obtained lithium-ion rechargeable battery  1  was subjected to the initial charge and the initial discharge. The initial charge and discharge conditions were the same as those explained using  FIGS. 5A and 5B . 
     In  FIG. 12 , similarly to  FIG. 5B  above, some gray spots in the storage layer  50  near the boundary between the storage layer  50  and the coating layer  60  are flattened with a shorter length in the thickness direction than a length in the plane direction and are relatively larger than other gray spots in the storage layer  50 . In  FIG. 12 , the white background portion is considered as corresponding to the porous part  51 , and the gray portions are considered as corresponding to the pores  52 , similarly to  FIG. 5B . The storage layer  50  shown in  FIG. 12  was 105 nm thick (after the initial discharge). 
     In this example too, both of the coating layer  60  and the negative electrode collector layer  70  had little change in gray level and thickness before and after the initial charge and discharge. 
     Conclusion of the First Embodiment 
     As described above, in the lithium-ion rechargeable battery  1  of the present embodiment, the coating layer  60  made of a metal or an alloy having an amorphous structure is stacked on the storage layer  50  facing the positive electrode layer  30  across the solid electrolyte layer  40 . This restrains lithium having moved from the positive electrode layer  30  to the storage layer  50  during the charging operation from leaking outside through the coating layer  60 , as compared to, for example, when the coating layer  60  having a polycrystalline structure is stacked on the storage layer  50 . 
     In the present embodiment, the porous storage layer  50  made of platinum is disposed on the solid electrolyte layer  40 . This restrains peeling inside the lithium-ion rechargeable battery  1  caused by expansion due to charging or contraction due to discharging, as compared to, for example, when a negative electrode layer made of silicon (Si) is disposed on the solid electrolyte layer  40 . 
     In the present embodiment, the negative electrode collector layer  70  made of platinum is disposed on the coating layer  60 . This restrains corrosion (deterioration) of the metal or alloy constituting the coating layer  60  caused by oxidation and the like, as compared to, for example, when the negative electrode collector layer  70  made of a material other than noble metals is disposed on the coating layer  60 . 
     In the lithium-ion rechargeable battery  1  of the present embodiment, the plane size of the storage layer  50  is larger than that of the positive electrode layer  30 , which faces the storage layer  50  across the solid electrolyte layer  40 . This restrains lithium ions from moving in a lateral direction (plane direction) when the lithium ions move from the positive electrode layer  30  to the storage layer  50 . This, in turn, restrains outside leakage of lithium ions from sides of the lithium-ion rechargeable battery  1 . 
     Though detailed description of this is not given here, when the storage layer  50  is made of any platinum group element (Ru, Rh, Pd, Os, Ir, Pt), gold (Au), or an alloy of some of these metals, the storage layer  50  can be made porous by charging and discharging and store lithium therein, similarly to the storage layer  50  solely composed of platinum (Pt). 
     Modifications of the First Embodiment 
     In the lithium-ion rechargeable battery  1  of the first embodiment, the substrate  10  and the solid electrolyte layer  40  cover the positive electrode collector layer  20  and the positive electrode layer  30 , and the solid electrolyte layer  40 , the coating layer  60 , and the negative electrode collector layer  70  cover the storage layer  50 . The present invention is, however, not limited to this configuration. 
     First Modification 
       FIG. 6  shows a sectional structure of the lithium-ion rechargeable battery  1  of a first modification of the first embodiment.  FIG. 6  shows the lithium-ion rechargeable battery  1  after the initial discharge, namely after completion of its structure (corresponding to  FIG. 1  of the first embodiment). 
     The first modification differs from the first embodiment in that, when viewed from above in  FIG. 6 , the plane size of the positive electrode collector layer  20  and the positive electrode layer  30  is almost equal to the plane size of the solid electrolyte layer  40 . In the first modification too, the storage layer  50  of the lithium-ion rechargeable battery  1  can be made porous (see  FIG. 6 ); this can be done by, in the same procedure as in the first embodiment (see  FIG. 2 ), first manufacturing the lithium-ion rechargeable battery  1  containing the dense storage layer  50  and then subjecting it to the initial charge and discharge following the film deposition. 
     Second Modification 
       FIG. 7  shows a sectional structure of the lithium-ion rechargeable battery  1  of a second modification of the first embodiment.  FIG. 7  shows the lithium-ion rechargeable battery  1  after the initial discharge, namely after completion of its structure (corresponding to  FIG. 1  of the first embodiment). 
     The second modification differs from the first embodiment in that, when viewed from above in  FIG. 7 , the plane size of the coating layer  60  is equal to the plane size of the storage layer  50 , and also the plane size of the negative electrode collector layer  70  is equal to the plane size of the coating layer  60 . In the second modification too, the storage layer  50  of the lithium-ion rechargeable battery  1  can be made porous (see  FIG. 7 ); this can be done by, in the same procedure as in the first embodiment (see  FIG. 2 ), first manufacturing the lithium-ion rechargeable battery  1  containing the dense storage layer  50  and then subjecting it to the initial charge and discharge following the film deposition. 
     Third Modification 
       FIG. 8  shows a sectional structure of the lithium-ion rechargeable battery  1  of a third modification of the first embodiment.  FIG. 8  shows the lithium-ion rechargeable battery  1  after the initial discharge, namely after completion of its structure (corresponding to  FIG. 1  of the first embodiment). 
     The third modification differs from the first modification in that, when viewed from above in  FIG. 8 , the plane size of the coating layer  60  is equal to the plane size of the storage layer  50 , and also the plane size of the negative electrode collector layer  70  is equal to the plane size of the coating layer  60 . In the third modification too, the storage layer  50  of the lithium-ion rechargeable battery  1  can be made porous (see  FIG. 8 ); this can be done by, in the same procedure as in the first embodiment (see  FIG. 2 ), first manufacturing the lithium-ion rechargeable battery  1  containing the dense storage layer  50  and then subjecting it to the initial charge and discharge following the film deposition. 
     Fourth Modification 
       FIG. 9  shows a sectional structure of the lithium-ion rechargeable battery  1  of a fourth modification of the first embodiment.  FIG. 9  shows the lithium-ion rechargeable battery  1  after the initial discharge, namely after completion of its structure (corresponding to  FIG. 1  of the first embodiment). 
     The fourth modification differs from the third modification in that, when viewed from above in  FIG. 9 , the plane size of the storage layer  50  is equal to the plane size of the solid electrolyte layer  40 . In the fourth modification too, the storage layer  50  of the lithium-ion rechargeable battery  1  can be made porous (see  FIG. 9 ); this can be done by, in the same procedure as in the first embodiment (see  FIG. 2 ), first manufacturing the lithium-ion rechargeable battery  1  containing the dense storage layer  50  and then subjecting it to the initial charge and discharge following the film deposition. 
     Second Embodiment 
     In the first embodiment, the storage layer  50  is made of a noble metal having a porous structure. In the second embodiment, the storage layer  50  is made of titanium (Ti) including multiple columnar crystals each extending in the thickness direction. In the present embodiment, similar elements to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. 
     [Configuration of the Lithium-Ion Rechargeable Battery] 
       FIGS. 10A and 10B  each show a sectional structure of the lithium-ion rechargeable battery  1  of the second embodiment. Similarly to the first embodiment, the lithium-ion rechargeable battery  1  of the present embodiment has a multilayer structure composed of multiple layers (films); its basic structure is formed by a so-called film deposition process, and the structure is completed by a first (initial) charging operation.  FIG. 10A  shows the lithium-ion rechargeable battery  1  after film deposition and before the initial charge, and  FIG. 10B  shows the lithium-ion rechargeable battery  1  after the initial charge. 
     (Configuration of the Lithium-Ion Rechargeable Battery after Film Deposition) 
     Similarly to the first embodiment, the lithium-ion rechargeable battery  1  after film deposition and before the initial charge includes the substrate  10 , the positive electrode collector layer  20 , the positive electrode layer  30 , the solid electrolyte layer  40 , the storage layer  50 , the coating layer  60 , and the negative electrode collector layer  70  stacked in this order, as shown in  FIG. 10A . 
     (Configuration of the Lithium-Ion Rechargeable Battery after the Initial Charge) 
     The basic configuration of the lithium-ion rechargeable battery  1  after the initial charge is almost similar to that of the lithium-ion rechargeable battery  1  after the film deposition and before the initial charge shown in  FIG. 10A , except that the lithium-ion rechargeable battery  1  after the initial charge includes a negative electrode  80  inside the storage layer  50 , as shown in  FIG. 10B . 
     The above constituents of the lithium-ion rechargeable battery  1  will be described in more detail below; the below description focuses on the storage layer  50  and the negative electrode  80  because the other constituents than the storage layer  50  and the negative electrode  80  are similar to those in the first embodiment. 
     (Storage Layer) 
     The storage layer  50  of the present embodiment is a solid thin film and has a structure in which multiple columnar crystals made of metal titanium (Ti) each extending in the thickness direction are arranged side by side. The columnar crystals of titanium constituting the storage layer  50  are typically hexagonal columnar crystals. 
     The storage layer  50  may have a thickness of 10 nm or more and 40 μm or less, for example. With a thickness of less than 10 nm, the storage layer  50  lacks sufficient capacity to store lithium. Meanwhile, when the storage layer  50  has a thickness of more than 40 μm, it increases internal resistance of the battery, which is disadvantageous for high speed charging/discharging. 
     While any known deposition method may be used to manufacture the storage layer  50 , such as various PVD and CVD methods, it is preferable to use a sputtering method in terms of efficient formation of an aggregate of titanium columnar crystals. 
     (Negative Electrode) 
     The negative electrode  80  contains a negative electrode active material that occludes lithium ions during a charge and releases lithium ions during a discharge. As described above, the negative electrode  80  of the present embodiment is formed inside the storage layer  50  by a charging operation. More specifically, lithium ions are stored at a boundary between each two adjacent columnar crystals, or a so-called crystal grain boundary, in the storage layer  50 , whereby the negative electrode  80  is formed. In the present embodiment, metal lithium itself functions as a negative electrode active material. 
     A preferred method for manufacturing the negative electrode  80  is to form (deposit) the negative electrode  80  by charging. 
     [Method for Manufacturing the Lithium-Ion Rechargeable Battery] 
     Below a description will be given of a method for manufacturing the lithium-ion rechargeable battery  1  shown in  FIGS. 10A and 10B . As described above, in the present embodiment, the basic structure of the lithium-ion rechargeable battery  1  shown in  FIG. 10A  is formed by a so-called film deposition process, and then the lithium-ion rechargeable battery  1  shown in  FIG. 10B  is obtained by the first (initial) charging operation. 
     First, the substrate  10  is mounted on a sputtering apparatus (not shown), and the positive electrode collector layer  20 , the positive electrode layer  30 , the solid electrolyte layer  40 , the storage layer  50 , the coating layer  60 , and the negative electrode collector layer  70  are stacked in this order on the substrate  10 . This results in the lithium-ion rechargeable battery  1  after the film deposition and before the initial charge as shown in  FIG. 10A . This lithium-ion rechargeable battery  1  is removed from the sputtering apparatus. 
     Then, the lithium-ion rechargeable battery  1  after the film deposition and before the initial charge as shown in  FIG. 10A  is given the initial charge. As a result, lithium is deposited on the crystal grain boundaries inside the storage layer  50  of the lithium-ion rechargeable battery  1  shown in  FIG. 10A . In other words, the negative electrode  80  made of lithium is formed inside the storage layer  50 , resulting in the lithium-ion rechargeable battery  1  after the initial charge as shown in  FIG. 10B . The charging and discharging operations of the lithium-ion rechargeable battery  1  will be detailed below. 
     [Operation of the Lithium-Ion Rechargeable Battery] 
     When the lithium-ion rechargeable battery  1  in a discharged state is charged, a positive electrode of a DC power source is connected to the substrate  10 , and a negative electrode of the DC power source is connected to the negative electrode collector layer  70 . Then, lithium ions constituting the positive electrode active material in the positive electrode layer  30  move through the solid electrolyte layer  40  to the storage layer  50 . In other words, in a charging operation, lithium ions move in the thickness direction of the lithium-ion rechargeable battery  1  (in the upward direction in  FIGS. 10A and 10B ). 
     At this time, lithium ions having moved from the positive electrode layer  30  toward the storage layer  50  reaches the boundary between the solid electrolyte layer  40  and the storage layer  50 . The storage layer  50  includes multiple columnar crystals made of metal titanium and extending in the thickness direction. These columnar crystals are arranged side by side. Thus, lithium ions having reached the boundary between the solid electrolyte layer  40  and the storage layer  50  enter the grain boundary between each two adjacent columnar crystals and move further in the thickness direction to get held within the storage layer  50 . 
     Some of lithium ions having entered the storage layer  50  go therethrough to reach the boundary between the storage layer  50  and the coating layer  60 . The coating layer  60  is made of an amorphous metal or alloy having the smaller number of grain boundaries than metal titanium (aggregate of columnar crystals) constituting the storage layer  50 . For this reason, lithium ions having reached the boundary between the storage layer  50  and the coating layer  60  are less likely to enter the coating layer  60 , and they remain stored within the storage layer  50 . 
     After the charging operation is finished, lithium ions having moved from the positive electrode layer  30  to the storage layer  50  are stored at the grain boundaries between columnar crystals in the storage layer  50 , where the lithium ions constitute the negative electrode  80 . 
     When the lithium-ion rechargeable battery  1  in a charged state is discharged (used), a positive side of a load is connected to the substrate  10  and a negative side of the load is connected to the negative electrode collector layer  70 . Then, lithium ions contained in the negative electrode  80  inside the storage layer  50  move in the thickness direction (in the downward direction in  FIGS. 10A and 10B ) through the solid electrolyte layer  40  to the positive electrode layer  30 , where the lithium ions constitute the positive electrode active material. Along with this, a direct current is supplied to the load. 
     After the discharging operation is finished, the negative electrode  80  inside the storage layer  50  does not disappear but remain because of some lithium that does not move during the discharging operation. 
     Conclusion of the Second Embodiment 
     As described above, in the lithium-ion rechargeable battery  1  of the present embodiment, the coating layer  60  made of a metal or an alloy having an amorphous structure is stacked on the storage layer  50  facing the positive electrode layer  30  across the solid electrolyte layer  40 . This restrains lithium having moved from the positive electrode layer  30  to the storage layer  50  during the charge operation from leaking outside through the coating layer  60 , as compared to, for example, when the coating layer  60  having a polycrystalline structure is stacked on the storage layer  50 . 
     In the present embodiment, the storage layer  50  composed of arranged columnar crystals of titanium is disposed on the solid electrolyte layer  40 . This restrains peeling inside the lithium-ion rechargeable battery  1  caused by expansion due to charging or contraction due to discharging, as compared to, for example, when a negative electrode layer made of silicon (Si) is disposed on the solid electrolyte layer  40 . 
     In the present embodiment, the negative electrode collector layer  70  made of platinum is disposed on the coating layer  60 . This restrains corrosion (deterioration) of the metal or alloy constituting the coating layer  60  caused by oxidation and the like, as compared to, for example, when the negative electrode collector layer  70  made of a material other than noble metals is disposed on the coating layer  60 . 
     Third Embodiment 
     In the first and second embodiments, the storage layer  50  that does not serve as a negative electrode by itself but has the function to store metal lithium serving as a negative electrode is disposed between the solid electrolyte layer  40  and the coating layer  60 . In the third embodiment, in contrast to the above embodiments, a layer serving as a negative electrode is disposed between the solid electrolyte layer  40  and the coating layer  60 . In the present embodiment, similar elements to those in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted. 
     [Configuration of the Lithium-Ion Rechargeable Battery] 
       FIG. 11  shows a sectional structure of the lithium-ion rechargeable battery  1  of the third embodiment. Similarly to the first and second embodiments, the lithium-ion rechargeable battery  1  of the present embodiment has a multilayer structure composed of multiple layers (films); unlike the first and second embodiments, however, the structure of the third embodiment is completed by a so-called film deposition process. 
     The lithium-ion rechargeable battery  1  of the present embodiment includes the substrate  10 , the positive electrode collector layer  20 , the positive electrode layer  30 , the solid electrolyte layer  40 , a negative electrode layer  90 , the coating layer  60 , and the negative electrode collector layer  70  stacked in this order. That is, the lithium-ion rechargeable battery  1  of the present embodiment includes the negative electrode layer  90  at the position corresponding to the storage layer  50  in the first and second embodiments. 
     The above constituents of the lithium-ion rechargeable battery  1  will be described in more detail below; the below description focuses on the negative electrode layer  90  because the other constituents than the negative electrode layer  90  are similar to those in the first and second embodiments. 
     (Negative Electrode Layer) 
     The negative electrode layer  90  (an example of the storage layer) is a solid thin film and contains a negative electrode active material that occludes lithium ions during a charge and releases lithium ions during a discharge. The negative electrode layer  90  of the present embodiment is made of doped amorphous silicon (Si). In the present embodiment, silicon serves as a negative electrode active material occluding and releasing lithium ions. The negative electrode layer  90  may, however, be made of a material other than silicon, and also the dopant is not essential. 
     The dopant for silicon constituting the negative electrode layer  90  is not limited to a particular one as long as the dopant increases conductivity of silicon; the dopant may be one or more of various elements. Among the elements, use is preferably made of zinc (Zn), cadmium (Cd), boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl), which serve as an acceptor to form a p-type negative electrode layer  90 , or use is preferably made of nitrogen (N), phosphorus (P), arsenic (As), sulfur (S), selenium (Se) and tellurium (Te), which serve as a donor to form an n-type negative electrode layer  90 . Among these, boron (B) is preferable in particular. 
     The negative electrode layer  90  may have a thickness of 10 nm or more and 20 μm or less, for example. With the negative electrode layer  90  having a thickness of less than 10 nm, the lithium-ion rechargeable battery  1  obtained therefrom has a too small capacity, which makes the lithium-ion rechargeable battery  1  impracticable. Meanwhile, when the negative electrode layer  90  has a thickness of more than 20 μm, it increases internal resistance of the battery, which is disadvantageous for high speed charging/discharging. The negative electrode layer  90  may, however, have a thickness of more than 20 μm when a large battery capacity is required of the lithium-ion rechargeable battery  1 . 
     While any known deposition method may be used to manufacture the negative electrode layer  90 , such as various PVD and CVD methods, it is preferable to use a sputtering method in terms of production efficiency. 
     [Method for Manufacturing the Lithium-Ion Rechargeable Battery] 
     Below a description will be given of a method for manufacturing the lithium-ion rechargeable battery  1  shown in  FIG. 11 . 
     First, the substrate  10  is mounted on a sputtering apparatus (not shown), and the positive electrode collector layer  20 , the positive electrode layer  30 , the solid electrolyte layer  40 , the negative electrode layer  90 , the coating layer  60 , and the negative electrode collector layer  70  are stacked in this order on the substrate  10 . This results in the lithium-ion rechargeable battery  1  as shown in  FIG. 11 . This lithium-ion rechargeable battery  1  is removed from the sputtering apparatus. 
     [Operation of the Lithium-Ion Rechargeable Battery] 
     When the lithium-ion rechargeable battery  1  in a discharged state is charged, a positive electrode of a DC power source is connected to the substrate  10 , and a negative electrode of the DC power source is connected to the negative electrode collector layer  70 . Then, lithium ions constituting the positive electrode active material in the positive electrode layer  30  move through the solid electrolyte layer  40  to the negative electrode layer  90 . In other words, in a charging operation, lithium ions move in the thickness direction of the lithium-ion rechargeable battery  1  (in the upward direction in  FIG. 11 ). 
     At this time, lithium ions having moved from the positive electrode layer  30  toward the negative electrode layer  90  reaches the boundary between the solid electrolyte layer  40  and the negative electrode layer  90 . The negative electrode layer  90  is made of silicon doped with boron as a dopant. Thus, lithium ions having reached the boundary between the solid electrolyte layer  40  and the negative electrode layer  90  get held in the negative electrode layer  90 . 
     Some of lithium ions having entered the negative electrode layer  90  go therethrough to reach the boundary between the negative electrode layer  90  and the coating layer  60 . The coating layer  60  is made of a metal or an alloy that is amorphized and thus has the reduced number of grain boundaries. For this reason, lithium ions having reached the boundary between the negative electrode layer  90  and the coating layer  60  are less likely to enter the coating layer  60 , and they remain stored within the negative electrode layer  90 . 
     When the lithium-ion rechargeable battery  1  in a charged state is discharged (used), a positive side of a load is connected to the substrate  10  and a negative side of the load is connected to the negative electrode collector layer  70 . Then, lithium ions present in the negative electrode layer  90  move in the thickness direction (in the downward direction in  FIG. 11 ) through the solid electrolyte layer  40  to the positive electrode layer  30 , where the lithium ions constitute the positive electrode active material. Along with this, a direct current is supplied to the load. 
     Conclusion of the Third Embodiment 
     As described above, in the lithium-ion rechargeable battery  1  of the present embodiment, the coating layer  60  made of a metal or an alloy having an amorphous structure is stacked on the negative electrode layer  90  facing the positive electrode layer  30  across the solid electrolyte layer  40 . This restrains lithium having moved from the positive electrode layer  30  to the negative electrode layer  90  during the charging operation from leaking outside through the coating layer  60 , as compared to, for example, when the coating layer  60  having a polycrystalline structure is stacked on the negative electrode layer  90 . 
     In the present embodiment, the negative electrode layer  90  is made of silicon containing boron. This increases the capacity of the lithium-ion rechargeable battery  1  at a given thickness (volume), as compared to, for example, when the negative electrode layer  90  is made of carbon (C). 
     In the present embodiment, the negative electrode collector layer  70  made of platinum is disposed on the coating layer  60 . This restrains corrosion (deterioration) of the metal or alloy constituting the coating layer  60  caused by oxidation and the like, as compared to, for example, when the negative electrode collector layer  70  made of a material other than noble metals is disposed on the coating layer  60 . 
     Other Notes 
     In the first to third embodiments, the coating layer  60  is disposed on the storage layer  50  (or the negative electrode layer  90 ). The present invention is, however, not limited to this configuration; a layer (an amorphous metal or alloy layer for preventing diffusion of lithium) similar to the coating layer  60  may be disposed on the positive electrode layer  30  side. In this case, the positive electrode layer  30  serves as an example of the storage layer. In one implementation, an amorphous metal or alloy layer may be disposed between the positive electrode collector layer  20  and the positive electrode layer  30 . In another implementation, the positive electrode collector layer  20  itself may be composed of an amorphous metal or alloy layer. 
     Still alternatively, a layer corresponding to the coating layer  60  may be disposed on both of the positive electrode layer  30  side and the storage layer  50  (or the negative electrode layer  90 ) side. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  Lithium-ion rechargeable battery 
               10  Substrate 
               20  Positive electrode collector layer 
               30  Positive electrode layer 
               40  Solid electrolyte layer 
               50  Storage layer 
               51  Porous part 
               52  Pore 
               60  Coating layer 
               70  Negative electrode collector layer 
               80  Negative electrode 
               90  Negative electrode layer