All-solid-state battery and method for manufacturing the same

Abstract

To provide an all-solid battery capable of reducing damage on a solid electrolyte layer at the time of charging / discharging and a manufacturing method therefor.SOLUTION: An all-solid battery 100 (single battery 9) includes: a power generation element part 1 disposed between a pair of collectors (positive electrode collector 2, negative electrode collector 3), the power generation element part obtained by stacking a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer (deposition layer 13) containing lithium alloy or lithium metal; and an elastic body 4 disposed so as to cover the outer periphery of the power generation element part 1. The elastic body 4 is formed from material having a Young's modulus lower than that of the solid electrolyte layer 12 and is disposed apart from the power generation element part 1.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery and a method for manufacturing the same. [Background technology]

[0002] All-solid-state batteries are formed by sandwiching a structure consisting of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer between a pair of current collector plates and then heating and compressing the structure. However, it is known that the solid electrolyte layer may soften during this process, which can lead to leakage to the outside.

[0003] Regarding the above problem, Patent Document 1 discloses an all-solid-state battery that reduces leakage of the solid electrolyte layer by arranging a heat-resistant insulating member between a pair of current collector plates so as to cover the outer periphery of the structure and forming it by heating and compressing it. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5131283 Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration of Patent Document 1, the structure is bonded to an insulating member. On the other hand, in an all-solid-state battery, the negative electrode layer expands and contracts in the thickness direction as the battery is repeatedly charged and discharged, and the structure also expands and contracts in the thickness direction accordingly. However, if the Young's moduli (degrees of expansion and contraction) of the solid electrolyte layer and the insulating member differ, the insulating member may apply stress to the solid electrolyte layer, potentially damaging it.

[0006] An object of the present invention is to provide an all-solid-state battery capable of reducing damage to a solid electrolyte layer during charging and discharging, and a method for manufacturing the same. [Means for solving the problem]

[0007] The all-solid-state battery according to the present invention includes a positive electrode layer, a solid electrolyte layer, and a lithium-ion battery between a pair of current collectors. A power generating element part is arranged in which a negative electrode layer containing a lithium alloy or lithium metal is laminated, and further The all-solid-state battery has an elastic body disposed so as to cover the outer periphery of the electric element. The elastic body is made of a material having a Young's modulus lower than that of the solid electrolyte layer, and a layer, the solid electrolyte layer, and the negative electrode layer, A gap is formed between the power generating element part consisting of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer and the elastic body. are. [Effects of the Invention]

[0008] According to the present invention, the elastic body has a lower Young's modulus than the solid electrolyte layer, so that the elastic body can expand and contract in accordance with the expansion and contraction of the power generating element during charging and discharging. At this time, since the solid electrolyte layer is separated from the elastic body, it is not subjected to stress from the elastic body, and damage to the solid electrolyte layer can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating a cell included in the all-solid-state battery of the first embodiment, where FIG. 1(a) is a plan view and FIG. 1(b) is a cross-sectional view. [Figure 2] 2A and 2B are schematic diagrams for explaining the arrangement of an elastic body in a unit cell included in the all-solid-state battery of the first embodiment, where FIG. 2A is a plan view and FIG. 2B is a cross-sectional view. [Figure 3] FIG. 3 is a schematic diagram for explaining the arrangement of an elastic adhesive in a cell included in the all-solid-state battery of the first embodiment, where FIG. 2(c) is a plan view and FIG. 3(b) is a cross-sectional view. [Figure 4] FIG. 4 is a cross-sectional view of a cell included in the all-solid-state battery of the first embodiment, with the left side of the dashed dotted line showing the state before charging and the right side showing the state after charging. [Figure 5] FIG. 5 is a cross-sectional view of a cell included in an all-solid-state battery of the comparative example, with the left side of the dashed dotted line showing the state before charging and the right side showing the state after charging. [Figure 6]FIG. 6 is a schematic diagram showing how cracks occur in the solid electrolyte layer. [Figure 7] FIG. 7 is a diagram showing the relationship between the stress applied to the solid electrolyte layer and the cracks that occur in the solid electrolyte layer. [Figure 8] FIG. 8 is a cross-sectional view of a cell included in the all-solid-state battery of the second embodiment, with the left side of the dashed dotted line showing the state before charging and the right side showing the state after charging. [Figure 9] FIG. 9 is a cross-sectional view of the all-solid-state battery according to the third embodiment. [Figure 10] FIG. 10 is a cross-sectional view of the all-solid-state battery according to the third embodiment when it is being charged. [Figure 11] FIG. 11 is a cross-sectional view of the all-solid-state battery according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Outline of the first embodiment] An all-solid-state battery 100 according to a first embodiment of the present invention will be described.

[0011] 1A and 1B are schematic diagrams illustrating a cell 9 included in the all-solid-state battery 100 of the first embodiment (a cell 9 manufactured by the manufacturing method for the all-solid-state battery 100 of the first embodiment), in which Fig. 1A is a plan view and Fig. 1B is a cross-sectional view. Note that Fig. 1A does not show the laminate layer 5 disposed on the upper side of Fig. 1B.

[0012] The all-solid-state battery 100 of this embodiment is a secondary battery that can be charged and discharged multiple times. The all-solid-state battery 100 is a so-called stacked-type all-solid-state battery 100 that houses therein a structure (see FIG. 9 and the like) in which multiple unit cells 9, which will be described below, are stacked and sealed with a laminate layer 5, which is a battery exterior material. By adopting a stacked-type structure, the battery can be made compact and have a high capacity.

[0013] However, the unit cells 9 housed in the all-solid-state battery 100 to which the present invention is applied do not necessarily have to be multi-layered, and may be single-layered. The unit cells 9 are configured in the shape of, for example, a circular or rectangular sheet before being housed in a battery exterior material. The appearance and internal electrical connection state (electrode structure) of the all-solid-state battery 100 of this embodiment are not particularly limited.

[0014] The appearance of the all-solid-state battery 100 may be circular, elliptical, or rectangular in plan view. Alternatively, it may be cylindrical in shape, in which a single-layer or multiple-layer cell 9 is wound and housed. The electrode structure of the all-solid-state battery 100 may be either a so-called non-bipolar type (internal parallel connection type) or a bipolar type (internal series connection type). In other words, the aspects of the all-solid-state battery 100 other than the configuration of the cell 9 described below are not particularly limited, regardless of whether they are publicly known or not.

[0015] The unit cell 9 has a configuration in which a power generating element 1, which is made up of a laminate of a negative electrode layer, a solid electrolyte layer 12, and a positive electrode layer 11, is sandwiched between a pair of opposing current collectors (negative electrode current collector 3, positive electrode current collector 2). In the unit cell 9, an elastic body 4 is disposed between the pair of current collectors (negative electrode current collector 3, positive electrode current collector 2) so as to cover the periphery of the power generating element 1 (positive electrode layer 11, solid electrolyte layer 12, negative electrode layer (deposit layer 13 (FIG. 4))).

[0016] The negative electrode current collector 3 has a rectangular shape, and a flexible extraction electrode 31 extends from one side of the rectangle. A negative electrode tab 32 (tab) serving as a rigid terminal is attached to the tip of the extraction electrode 31.

[0017] The negative electrode layer is formed as a deposit layer 13 on the surface of the negative electrode current collector 3 facing the positive electrode current collector 2 when the unit cell 9 is charged, and disappears when the unit cell 9 is discharged. The negative electrode layer (deposit layer 13) is composed of a negative electrode active material containing at least a lithium alloy or lithium metal. As such, when the unit cell 9 is charged and discharged, the negative electrode layer (deposit layer 13) appears and disappears, and the dimension in the thickness direction changes. Note that as another form of the negative electrode layer, a solid electrolyte containing lithium metal or a lithium alloy may be disposed as the negative electrode layer on the surface of the negative electrode current collector 3 facing the positive electrode current collector 2.

[0018] The positive electrode current collector 2 has a rectangular shape, and a flexible extraction electrode 21 extends from one side of the rectangle. A positive electrode tab 22 (tab) serving as a rigid terminal is attached to the tip of the extraction electrode 21.

[0019] The positive electrode layer 11 is formed on the surface of the positive electrode current collector 2 facing the negative electrode current collector 3. The positive electrode layer 11 preferably contains a sulfur-containing positive electrode active material. The type of sulfur-containing positive electrode active material is not particularly limited, but examples include elemental sulfur (S) as well as particles or thin films of organic sulfur compounds or inorganic sulfur compounds, as long as it is a substance that can release lithium ions during charging and absorb lithium ions during discharging by utilizing the oxidation-reduction reaction of sulfur.

[0020] The solid electrolyte layer 12 contains a solid electrolyte as a main component and is a layer interposed between the above-mentioned negative electrode layer (deposit layer 13) and positive electrode layer 11. Examples of the solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes, with sulfide solid electrolytes being preferred.

[0021] The laminate layer 5 seals the cell 9 (particularly the power generating element 1). The sealing configuration of the laminate layer 5 is the same as that shown in FIG. 8, which will be described later. The laminate layer 5 is used to prevent damage to the power generating element 1 and to protect the solid electrolyte layer 12, the negative electrode layer, and the positive electrode layer 11 from moisture in the atmosphere. Furthermore, if the solid electrolyte layer 12 is a sulfide, hydrogen sulfide may be generated by reaction with moisture. Therefore, the laminate layer 5 serves to prevent the hydrogen sulfide gas from diffusing to the outside of the cell 9.

[0022] 2A and 2B are schematic diagrams for explaining the arrangement of the elastic body 4 in the cell 9 included in the all-solid-state battery 100 of the first embodiment, where FIG. 2A is a plan view and FIG. 2B is a cross-sectional view.

[0023] The elastic body 4 is formed from an insulating resin such as polyimide (e.g., Kapton (registered trademark)) or PTFE (polytetrafluoroethylene). The elastic body 4 is formed in a rectangular frame shape when the power generating element 1 is rectangular in plan view, and is formed in a circular ring shape when the power generating element 1 is circular in plan view. The elastic body 4 is arranged to cover the entire periphery of the power generating element 1, thereby preventing leakage to the outside of the power generating element 1. The elastic body 4 is also arranged so as to be spaced apart from the power generating element 1 in plan view. The elastic body 4, including the materials mentioned above, is preferably one with a Young's modulus (modulus of longitudinal elasticity) of 5 GPa or less.

[0024] FIG. 3 is a schematic diagram for explaining the arrangement of the elastic adhesive 42 in the cell 9 included in the all-solid-state battery 100 of the first embodiment, where FIG. 2(3) is a plan view and FIG. 3(b) is a cross-sectional view.

[0025] The elastic adhesive 42 may be a resin-based adhesive such as an acrylic-modified silicone resin-based elastic adhesive (e.g., Super X (registered trademark) No. 8008, Super XG No. 777, SX720W manufactured by Cemedine Co., Ltd.), a two-component mixed curing type epoxy-modified silicone-based elastic adhesive (e.g., EP001K manufactured by Cemedine Co., Ltd.), or other thermosetting resin such as an epoxy resin or silicone resin. As shown in Fig. 3, the elastic adhesive 42 is applied to both sides of the elastic body 4.

[0026] [Manufacturing process of single cell 9] The manufacturing process of the unit cell 9 is carried out in the following order: (1) forming the positive electrode layer 11, (2) forming the negative electrode layer, (3) disposing the elastic body 4, (4) heat compression, (5) tab welding, and the like.

[0027] (1) Formation of the positive electrode layer 11 Aluminum foil (thickness: 10 to 20 μm) is prepared as the material for the positive electrode current collector 2 and the positive electrode extraction electrode 21. Lithium nickel-cobalt manganese oxide, a Li2S-P2S5-based sulfide solid electrolyte, and a binder (PVDF: polyvinylidene fluoride) are prepared as the material for the positive electrode layer 11, and these are placed in a planetary ball mill to be pulverized and mixed to form a mixture. The mixture is coated onto aluminum foil and dried at 80°C using a hot plate until the solvent evaporates. The foil is then roll-pressed under the desired linear pressure and temperature control, and then cut (punched) to a predetermined size to form the positive electrode layer 11 (positive electrode current collector 2).

[0028] (2) Formation of the negative electrode layer / solid electrolyte layer 12 Stainless steel foil (or copper foil) is prepared as the material for the negative electrode current collector 3 and the negative electrode extraction electrode 31, and is used as a lithium deposition-type negative electrode layer (negative electrode current collector 3 on which deposition layer 13 is deposited as the negative electrode layer). A slurry composed of a Li2S-P2S5-based sulfide solid electrolyte containing lithium metal (or lithium alloy), a binder (SBR: styrene butadiene rubber), and a solvent is then prepared on the stainless steel foil. The slurry is then coated on the stainless steel foil and dried, after which it is roll-pressed under the desired linear pressure and temperature control, and cut (punched) to a predetermined size to form a negative electrode layer (negative electrode current collector 3) on which a solid electrolyte layer 12 is disposed.

[0029] (3) Arrangement of elastic body 4 Kapton (registered trademark) or PTFE is prepared as the material for the elastic body 4, and the material is processed into a frame shape so that the positive electrode layer 11 is disposed inside, to form the elastic body 4. A member in which the elastic body 4 is disposed between the positive electrode current collector 2 and the negative electrode current collector 3 is assembled, and an elastic adhesive 42 (e.g., a thermosetting resin) is injected by underfilling between the positive electrode current collector 2 and the elastic body 4 and between the negative electrode current collector 3 and the elastic body 4. The elastic adhesive 42 is then cured at a curing temperature of 100 to 150°C for a curing time of 1 to 2 hours.

[0030] (4) Heat compression The above-mentioned members are compressed for 1 to 2 hours to form the unit cell 9. At this time, the members are heated at 100 to 150° C. to ensure the adhesive strength of the elastic adhesive 42.

[0031] (5) Tab welding, etc. In the formed single cell 9, a positive electrode tab 22 (thickness 200 to 400 μm) is attached to the tip of the extraction electrode 21, a negative electrode tab 32 (thickness 200 to 400 μm) is attached to the tip of the extraction electrode 31, and the single cell 9 is laminated and vacuum sealed with a laminate layer 5 to complete the single cell 9.

[0032] [Comparative example cell 9] Fig. 5 is a cross-sectional view of a cell 9 included in an all-solid-state battery 100 of a comparative example, with the left side of the dashed dotted line before charging and the right side after charging. Fig. 6 is a schematic diagram of when a crack 121 occurs in a solid electrolyte layer 12. Fig. 7 is a diagram showing the relationship between stress applied to the solid electrolyte layer 12 and the crack 121 that occurs in the solid electrolyte layer 12.

[0033] As described above, it is known that lithium is deposited on the negative electrode side when the cell 9 is charged. In this case, lithium is deposited on the solid electrolyte layer 12 side and appears as a deposit layer 13 in the power generating element part 1, and the power generating element part 1 expands in the thickness direction by the amount of the deposit layer 13 (right side of Figure 5).

[0034] The comparative example shown in FIG. 5 has the same structure as that of Patent Document 1. In the comparative example, the power generating element 1 and the elastic body 4 are in contact (bonded). In the comparative example, the power generating element 1 expands and contracts in the thickness direction when charging and discharging are repeated, and the elastic body 4 expands and contracts in the thickness direction accordingly. If the Young's modulus (modulus of longitudinal elasticity) of the elastic body 4 differs from that of the solid electrolyte layer 12 of the power generating element 1, the magnitude of expansion and contraction of the power generating element 1 differs from that of the elastic body 4. This may cause stress (especially tensile stress) to be applied to the side surface of the solid electrolyte layer 12, which may damage the solid electrolyte layer 12 in the form of, for example, cracks 121.

[0035] The inventors of the present application used comparative examples to study the stress that occurs during charging and the cracks 121 that may occur in the solid electrolyte layer 12. First, the thickness of the elastic body 4 (and the power generating element 1) when the cell 9 is at a 0% charge level is taken as L + ΔL, and the stress is studied when the thickness of the elastic body 4 when the cell 9 is at a 100% charge level is L + ΔL. A cell 9 was prepared in which the thickness of the elastic body 4 when the cell 9 is at a 0% charge level was 128.6 μm. It was confirmed that the thickness of the elastic body 4 increased by 21.5 μm when the cell 9 was charged. The open-circuit voltage of the cell 9 after charging was 4.25 V. In this case, the strain ε applied to the elastic body 4 was 21.5 / 128.6 = 0.168.

[0036] As shown in Figure 6, it is assumed that the thickness of the power generating element part 1 is equal to the thickness of the elastic body 4, and the increase ΔL is due to the generation of the precipitate layer 13, and the change in thickness of the solid electrolyte layer 12 and the positive electrode layer 11 of the power generating element part 1 is ignored.

[0037] Then, the strain stress σ that the solid electrolyte layer 12 connected (bonded) to the elastic body 4 receives from the elastic body 4 is σ=0.168×23=3.853 Gpa, assuming that the Young's modulus of the solid electrolyte (argyoridite) is 23 Gpa.

[0038] On the other hand, when PTFE is used as the elastic body 4, its Young's modulus is 0.5 Gpa, so the strain stress (tensile stress) σ that the elastic body 4 receives from the power generation element 1 is σ = 0.168 × 0.5 = 0.084 Gpa. When Kapton (registered trademark) is used as the elastic body 4, its Young's modulus is 3.3 Gpa, so the strain stress σ that the elastic body 4 receives from the power generation element 1 is σ = 0.168 × 3.3 = 0.554 Gpa.

[0039] In either case, when the strain stress applied to the solid electrolyte layer 12 is greater than the strain stress applied to the elastic body 4, a crack 121 (cleavage) occurs in the solid electrolyte layer 12.

[0040] Solid electrolytes are materials with low toughness, like ceramics and glass, and the fracture surface (cleavage surface) of such materials is flat with almost no evidence of plastic deformation. To understand the mechanism by which the crack 121 propagates without plastic deformation, it is necessary to consider the local stress increase ahead of the tip of the crack 121.

[0041] According to the theory of continuum elasticity, stress concentration occurs near the tip of a sharp crack121, and the local stress is σ Local =σ(1+(a / (2r)) 1 / 2 ) and is represented by the curve shown in Figure 7, where σ is the average tensile stress applied to the entire material, a is the length of the crack 121, and r is the distance from the tip of the crack 121.

[0042] As shown in Figure 7, σLocal rises sharply near the tip of the crack 121, but materials such as ceramics and glass have high yield strengths and do not easily undergo plastic deformation, so the tensile stress near the tip of the crack 121 exceeds the ideal strength and breaks the interatomic bonds within the material. If this severing of interatomic bonds occurs continuously, the material cleaves. Note that with repeated charge and discharge, the crack 121 extends in various directions and reaches the negative electrode layer (precipitation layer 13) and the positive electrode layer 11. If lithium metal (lithium dendrite) enters the crack 121, there is a risk of a short circuit between the negative electrode layer and the positive electrode layer 11 via the lithium metal.

[0043] FIG. 4 is a cross-sectional view of the cell 9 included in the all-solid-state battery 100 of the first embodiment, with the left side showing the state before charging and the right side showing the state after charging.

[0044] On the other hand, as shown in FIG. 4 , in the all-solid-state battery 100 (single cell 9) of this embodiment, the elastic body 4 has a lower Young's modulus than the solid electrolyte layer 12. This allows the elastic body 4 (and the elastic adhesive 42) to expand and contract in accordance with the expansion and contraction of the power generation element 1 during charge and discharge. Here, the elastic body 4 (and the elastic adhesive 42) expands in the thickness direction by the thickness of the deposition layer 13. Therefore, the power generation element 1, the positive electrode current collector 2, and the negative electrode current collector 3 do not deform in any direction other than the thickness direction, thereby suppressing deterioration over time due to repeated charge and discharge. Furthermore, when the power generation element 1 expands (and contracts), the solid electrolyte layer 12 is separated from the elastic body 4, so it is not subjected to tensile stress from the elastic body 4. This reduces damage (cracks 121) to the solid electrolyte layer 12. Additionally, short-circuiting between the positive electrode layer 11 and the negative electrode layer, which may occur when lithium metal precipitates during charge and penetrates into the cracks 121, can also be suppressed.

[0045] [Effects of the first embodiment] According to the all-solid-state battery 100 (single cell 9) of the first embodiment, a power generation element 1 is disposed between a pair of current collectors (positive electrode current collector 2, negative electrode current collector 3), and is formed by laminating a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer (precipitation layer 13) containing a lithium alloy or lithium metal. In the all-solid-state battery 100, further, an elastic body 4 is disposed so as to cover the outer periphery of the power generation element 1. The elastic body 4 is formed of a material having a lower Young's modulus than the solid electrolyte layer 12, and is disposed at a distance from the power generation element 1.

[0046] Furthermore, according to the manufacturing method of the all-solid-state battery 100 (single cell 9) of the first embodiment, in the manufacturing method of the all-solid-state battery 100, a power generation element 1 is disposed between a pair of current collectors (positive electrode current collector 2, negative electrode current collector 3), and the power generation element 1 is formed by laminating a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer (precipitation layer 13) containing a lithium alloy or lithium metal, and the elastic body 4 is disposed so as to cover the outer periphery of the power generation element 1. In this manufacturing method of the all-solid-state battery 100, the elastic body 4 is formed from a material having a lower Young's modulus than the solid electrolyte layer 12, and is disposed at a distance from the power generation element 1.

[0047] With the above-described configuration and method, the elastic body 4 has a lower Young's modulus than the solid electrolyte layer 12, so that the elastic body 4 can expand and contract in accordance with the expansion and contraction of the power generation element 1 during charge and discharge. At this time, since the solid electrolyte layer 12 is separated from the elastic body 4, it is not subjected to stress (especially tensile stress) from the elastic body 4, and damage (cracks 121) to the solid electrolyte layer 12 can be reduced. In addition to the above, short circuits between the positive electrode layer 11 and the negative electrode layer caused by lithium metal precipitated during charge entering the cracks 121 can also be suppressed.

[0048] In the first embodiment, an elastic adhesive 42 is disposed between the elastic body 4 and the current collectors (positive electrode current collector 2, negative electrode current collector 3). This allows the elastic body 4 and the current collectors (positive electrode current collector 2, negative electrode current collector 3) to be stably fixed together. It also allows the stress generated when the power generating element 1 is deformed to be alleviated (absorbed). By using the elastic adhesive 42 in this way, the elastic body 4 and the current collectors (positive electrode current collector 2, negative electrode current collector 3) can be fixed together while expanding and contracting in accordance with the expansion and contraction of the power generating element 1 during charge and discharge.

[0049] In the first embodiment, the elastic adhesive 42 is an acrylic-modified silicone resin-based elastic adhesive or a two-component mixed curing type epoxy-modified silicone-based elastic adhesive. This results in a material with a low Young's modulus (longitudinal elastic modulus), allowing it to expand and contract in accordance with the expansion and contraction of the power generating element 1 during charge and discharge. Furthermore, even when the power generating element 1 expands during charge and discharge, it can expand and contract together with the elastic body 4 while fixing the elastic body 4 and the current collector. In addition, because it is a highly versatile adhesive material, it can be applied to the elastic body 4 and the current collectors (positive electrode current collector 2, negative electrode current collector 3) at low cost.

[0050] In the first embodiment, the Young's modulus of the elastic body 4 is 5 GPa or less. By using an elastic body 4 with a Young's modulus of 5 GPa or less, such as Kapton (registered trademark) or PTFE, the elastic body 4 can expand and contract sufficiently in accordance with the expansion and contraction of the power generation element unit 1 during charging and discharging, thereby suppressing the concentration of stress on the power generation element unit 1 and the occurrence of cracks 121 (cleavage).

[0051] In the first embodiment, the solid electrolyte layer 12 is made of a sulfide-based solid electrolyte material. Since the sulfide-based solid electrolyte is a material with high lithium ion conductivity, the internal resistance is small, resulting in an all-solid-state battery 100 (cell 9) with high efficiency in gunfire.

[0052] [Second embodiment] Fig. 8 is a cross-sectional view of a cell 9 included in an all-solid-state battery 100 of the second embodiment, with the left side of the dashed dotted line showing the state before charging and the right side showing the state after charging. Fig. 8 is a cross-sectional view of the cell 9 viewed from the same perspective as Fig. 1(b), and the cell 9 of the second embodiment has a similar configuration to that of the first embodiment. Note that the positive electrode current collector 2 and the negative electrode current collector 3 are not shown in Fig. 8.

[0053] The cell 9 of the second embodiment has a configuration in which the outer periphery of the positive electrode layer 11 is covered with the solid electrolyte layer 12. This reduces the risk of leakage of the positive electrode layer 11 and short-circuiting with the negative electrode layer.

[0054] In the second embodiment, when the battery is charged, a deposit layer 13 (negative electrode layer) appears on the negative electrode side, the elastic body 4 (and the elastic adhesive 42) expands by the thickness of the deposit layer 13, and the thickness of the cell 9 also increases.

[0055] [Third embodiment] Fig. 9 is a cross-sectional view of the all-solid-state battery 100 of the third embodiment. Fig. 10 is a cross-sectional view of the all-solid-state battery 100 of the third embodiment when it is being charged.

[0056] The all-solid-state battery 100 of the third embodiment is obtained by preparing a plurality of (ten in the figure) unit cells 9 before sealing with the laminate layer 5 of the second embodiment (or the first embodiment), stacking the cells 9 while alternately inverting them so that the positive electrode layers 11 (positive electrode current collectors 2) face each other or the negative electrode layers (negative electrode current collectors 3) face each other in adjacent unit cells 9, sealing the stack of unit cells 9 obtained by stacking with the laminate layer 5, and pressing the sealed stack using a restraining jig 6.

[0057] Additionally, the positive electrode tabs 22 at the ends of the extraction electrodes 21 are connected (welded) in a stacked state. Similarly, the negative electrode tabs 32 at the ends of the extraction electrodes 31 are also connected (welded) in a stacked state. That is, in the third embodiment, all of the cells 9 are connected in parallel. Here, the positive electrode tabs 22 and the negative electrode tabs 32 are disposed at central positions in the thickness direction.

[0058] In the all-solid-state battery 100 of the third embodiment, when the battery is charged, the entire laminate expands in the thickness direction, but the positional relationship between the positive electrode tab 22 and the negative electrode tab 32 and the adjacent unit cells 9 in the thickness direction hardly changes before and after charging the all-solid-state battery 100. Therefore, with respect to the unit cells 9, no stress is generated that pulls the power generating element unit 1 toward the positive electrode tab 22 via the extraction electrode 21, and no stress is generated that pulls the power generating element unit 1 toward the negative electrode tab 32 via the extraction electrode 31.

[0059] Meanwhile, the positional relationship between the two cells 9 adjacent to the restraining jig 6 and the positive electrode tab 22 and negative electrode tab 32 changes significantly when the all-solid-state battery 100 is charged. Therefore, for the two cells 9 adjacent to the restraining jig 6, a strong stress is generated that pulls the power generating element unit 1 toward the positive electrode tab 22 via the extraction electrode 21, and a strong stress is generated that pulls the power generating element unit 1 toward the negative electrode tab 32 via the extraction electrode 31.

[0060] However, in this embodiment, the elastic body 4a of the cell 9 adjacent to the restraining jig 6 is made of a material having a higher Young's modulus than the elastic bodies 4 of the other cells 9. For example, Kapton (registered trademark) (3.3 Gpa) is used as the elastic body 4a adjacent to the restraining jig 6, and for example, PTFE (0.5 Gpa) is used as the other elastic bodies 4.

[0061] The elastic body 4a with a high Young's modulus can reduce displacement not only in response to stress in the thickness direction of the cell 9 but also in response to stress in the planar direction. Therefore, the elastic body 4a can suppress the stress that pulls the power generating element unit 1 toward the positive electrode tab 22 via the extraction electrode 21 and the stress that pulls the power generating element unit 1 toward the negative electrode tab 32 via the extraction electrode 31. Therefore, the stress that pulls the power generating element unit 1 toward the positive electrode tab 22 via the extraction electrode 21 and the stress that pulls the power generating element unit 1 toward the negative electrode tab 32 via the extraction electrode 31 can be reduced.

[0062] As a result, the tensile stress generated during charging and discharging can be reduced for the power generating element 1 of the cell 9 adjacent to the restraining jig 6, thereby suppressing damage to the power generating element 1, particularly breakage of the outer corners 122.

[0063] [Fourth embodiment] FIG. 11 is a cross-sectional view of the all-solid-state battery 100 according to the fourth embodiment.

[0064] The all-solid-state battery 100 of the fourth embodiment is obtained by preparing a plurality (ten in the figure) of unit cells 9 before sealing with the laminate layer 5 of the first embodiment (or the second embodiment), stacking the cells 9 while alternately inverting them so that the positive electrode layers 11 (positive electrode current collectors 2) face each other or the negative electrode layers (negative electrode current collectors 3) face each other in adjacent unit cells 9, sealing the stack of unit cells 9 obtained by stacking with the laminate layer 5, and pressing the sealed stack using a restraining jig 6. Note that the laminate layer 5, extraction electrode 31, and negative electrode tab 32 that appear on the left side of the unit cells 9 in the figure are omitted from the illustration.

[0065] Furthermore, the positive electrode tabs 22 at the tips of the extraction electrodes 21 extending from the positive electrode current collector 2 of each cell 9 are stacked and connected, and the positive electrode tabs 22 are positioned closer to the restraining jig 6 shown in the lower part of Fig. 11. Although not shown, the negative electrode tabs 32 at the tips of the extraction electrodes 31 extending from the negative electrode current collector 3 of each cell 9 are stacked and connected, and the negative electrode tabs 32 are positioned closer to the restraining jig 6 shown in the lower part of Fig. 11. Thus, in the fourth embodiment as well, all of the cells 9 are connected in parallel.

[0066] In the all-solid-state battery 100 of the fourth embodiment, when charging is performed, the entire laminate expands in the thickness direction, but the positional relationship between the adjacent cells 9 in the thickness direction at the positive electrode tab 22 and the negative electrode tab 32, i.e., the cell 9 adjacent to the restraining jig 6 illustrated on the lower side of Fig. 11, remains almost unchanged before and after charging the all-solid-state battery 100. Therefore, with respect to the cell 9, no stress is generated that pulls the power generating element unit 1 toward the positive electrode tab 22 via the extraction electrode 21, and no stress is generated that pulls the power generating element unit 1 toward the negative electrode tab 32 via the extraction electrode 31.

[0067] On the other hand, in the unit cells 9 that are separated from the positive electrode tab 22 and the negative electrode tab 32 in the thickness direction, particularly the unit cells 9 adjacent to the restraining jig 6 illustrated in the upper part of Fig. 11, the positional relationship between the positive electrode tab 22 and the negative electrode tab 32 changes significantly when the all-solid-state battery 100 is charged. Therefore, in the unit cells 9, a strong stress is generated that pulls the power generating element unit 1 toward the positive electrode tab 22 via the extraction electrode 21, and a strong stress is generated that pulls the power generating element unit 1 toward the negative electrode tab 32 via the extraction electrode 31.

[0068] However, in the fourth embodiment, the elastic body 4a of the cell 9 adjacent to the restraining jig 6 shown in the upper part of Fig. 11 is made of a material having a higher Young's modulus than the elastic bodies 4 of the other cells 9. For example, Kapton (registered trademark) (3.3 Gpa) is used for the elastic body 4a adjacent to the restraining jig 6 on the upper side of Fig. 11, and for example, PTFE (0.5 Gpa) is used for the other elastic bodies 4.

[0069] For the same reasons as in the third embodiment, in the fourth embodiment, the tensile stress generated during charging and discharging can be reduced for the power generating element portion 1 of the single battery 9 adjacent to the restraining jig 6 shown in the upper part of Figure 11, thereby suppressing damage to the power generating element portion 1, particularly breakage of the outer corners 111.

[0070] Furthermore, in the fourth embodiment, the entire all-solid-state battery 100 is heated when the positive electrode tab 22 and the negative electrode tab 32 are welded, respectively, and the heat causes the all-solid-state battery 100 to expand in the thickness direction. Even in this case, the positional relationship in the thickness direction between the cell 9 adjacent to the restraining jig 6 illustrated in the upper part of Fig. 11 and the positive electrode tab 22 and the negative electrode tab 32 changes significantly. However, by using an elastic body 4a with a high Young's modulus as the elastic body 4 of the cell 9 as described above, it is possible to reduce the tensile stress generated when the positive electrode tab 22 and the negative electrode tab 32 are welded, and to suppress damage to the power generation element unit 1, in particular breakage of the outer circumferential corners 111.

[0071] According to the all-solid-state batteries 100 of the third and fourth embodiments, a plurality of unit cells 9 each including a pair of current collectors (positive electrode current collector 2, negative electrode current collector 3), a power generating element portion 1, and an elastic body 4 are stacked, the unit cells 9 are pressed in the thickness direction by a restraining jig 6, and extraction electrodes (extraction electrodes 21, 31) extending from the current collectors (positive electrode current collector 2, negative electrode current collector 3) are joined by tabs (positive electrode tab 22, negative electrode tab 32). In the all-solid-state battery 100 formed by this, of the elastic bodies 4, the Young's modulus of the elastic body 4a of the unit cell 9 closest to the restraining jig 6, or the elastic body 4a of the unit cell 9 separated from the tabs (positive electrode tab 22, negative electrode tab 32) in the thickness direction (particularly, the elastic body 4a of the unit cell 9 closest to the restraining jig 6) is higher than the Young's modulus of the elastic body 4 of the unit cell 9 adjacent to the tabs (positive electrode tab 22, negative electrode tab 32) in the thickness direction.

[0072] This reduces the tensile stress that may be applied to the power generating element 1 of the cell 9 that is separated from the tabs (positive electrode tab 22, negative electrode tab 32) in the thickness direction during charging and discharging, thereby suppressing damage to the power generating element 1, particularly breakage of the outer circumferential corners 122 (corner 111). Furthermore, the tensile stress that occurs during welding of the tabs (positive electrode tab 22, negative electrode tab 32) to the power generating element 1 can be reduced, thereby suppressing damage to the power generating element 1, particularly breakage of the outer circumferential corners 111.

[0073] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. Furthermore, the above embodiments can be combined as appropriate. [Explanation of symbols]

[0074] 100 solid state battery 1 Power generation element 11 Positive electrode layer 12 Solid electrolyte 13 Precipitated layer 2 Positive electrode current collector 3 Negative electrode current collector 4 Elastic Body 9 D cells

Claims

1. An all-solid-state battery in which a power generating element part is disposed between a pair of current collectors, the power generating element part being formed by laminating a positive electrode layer, a solid electrolyte layer, and a negative electrode layer containing a lithium alloy or lithium metal, and an elastic body is further disposed so as to cover the outer periphery of the power generating element part, the elastic body is formed of a material having a lower Young's modulus than the solid electrolyte layer, and is disposed apart from the positive electrode layer, the solid electrolyte layer, and the negative electrode layer, and a gap is formed between the power generation element unit consisting of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer and the elastic body.

2. The all-solid-state battery according to claim 1 , wherein an elastic adhesive is disposed between the elastic body and the current collector.

3. 3. The all-solid-state battery according to claim 2, wherein the elastic adhesive is an acrylic-modified silicone resin-based elastic adhesive or a two-part mixed curing type epoxy-modified silicone-based elastic adhesive.

4. The all-solid-state battery according to claim 1 , wherein the Young's modulus of the elastic body is 5 GPa or less.

5. 5. The all-solid-state battery according to claim 1, wherein the solid electrolyte layer is made of a sulfide-based solid electrolyte material.

6. In an all-solid-state battery formed by stacking a plurality of unit cells each including a pair of the current collectors, the power generating element portion, and the elastic body, pressing the unit cells in a thickness direction with a restraining jig, and connecting extraction electrodes extending from the current collectors with tabs, 6. The all-solid-state battery according to claim 1, wherein the Young's modulus of the elastic body of the unit cell that is closest to the restraining jig is higher than the Young's modulus of the elastic body of the unit cell that is adjacent to the tab in the thickness direction.

7. A method for manufacturing an all-solid-state battery, comprising: disposing a power generating element unit between a pair of current collectors, the power generating element unit being formed by laminating a positive electrode layer, a solid electrolyte layer, and a negative electrode layer containing a lithium alloy or lithium metal; and further disposing an elastic body so as to cover the outer periphery of the power generating element unit; a power generating element section including the positive electrode layer, the solid electrolyte layer, and the negative electrode layer; a power generating element section including the positive electrode layer, the solid electrolyte layer, and the negative electrode layer; a power generating element section including the positive electrode layer, the solid electrolyte layer, and the negative electrode layer;

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