All-solid-state batteries

Abstract

Provided is an all-solid-state battery with which it is possible to sufficiently ensure an electrical contact between an external can and a power generation element, and an electrical contact between a sealing can and the power generation element, and it is possible to prevent damage to a positive electrode layer or a negative electrode layer. This all-solid-state battery 1 comprises: an external can 2 having a bottom part 21 and a cylindrical side wall part 22; a negative electrode can 3 having a flat surface part 31 and a circumferential wall part 32; power generation elements 4 disposed between the external can 2 and a sealing can 3; a gasket 6 disposed between the cylindrical side wall part 22 and the circumferential wall part 32; and restorable conductive sheets 5. The bottom part 21 of the external can 2 has formed thereon a recessed part 211 that is depressed outward. The restorable conductive sheets 5 are respectively disposed between the power generation element 4 and the inner bottom surface of the recessed part 211, and between the power generation element 4 and the flat surface part 31 of the sealing can 3.

Description

[Technical Field]

[0001] The present disclosure relates to all-solid-state batteries. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 11-144761 discloses a lithium-ion secondary battery in which a positive electrode and a negative electrode are arranged opposite each other with a separator interposed therebetween, and the battery is housed in a battery case made up of a positive electrode can and a negative electrode can, and the positive electrode can and negative electrode can are crimped together via a gasket (Patent Document 1). In the lithium-ion secondary battery, an elastic body coated with a conductor is disposed between the positive electrode and the positive electrode can and between the negative electrode and the negative electrode can. This ensures sufficient contact area between the positive electrode and the positive electrode can and between the negative electrode and the negative electrode can, and reduces stress when crimping the positive electrode can and negative electrode can, preventing cracking of the positive electrode and negative electrode.

[0003] Japanese Patent Application Laid-Open Publication No. 2003-151511 discloses a flat nonaqueous electrolyte battery including a positive electrode can, a negative electrode can, and a positive electrode material, a negative electrode material, and a separator housed in both cans, with a gasket disposed between the periphery of the positive electrode can and the periphery of the negative electrode can. The flat nonaqueous electrolyte battery has a sealing wall that contacts the gasket on the periphery of the bottom wall of the positive electrode can, and the positive electrode material is housed in a recess located radially inward from the sealing wall. This prevents the sealing wall from being affected by expansion and deformation of the bottom wall of the recess in high-temperature environments. Furthermore, the ratio of the inside diameter D1 of the housing portion on the top wall of the negative electrode can to the inside diameter D2 of the recess is set to D2 / D1 = 1.01 to 1.2, thereby preventing the periphery of the positive electrode material from climbing over the opening edge of the recess and causing damage during the assembly process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-144761 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-151511 Summary of the Invention

[0005] However, the lithium-ion secondary battery of Patent Document 1 uses an elastic body whose surface is coated with a conductor. In other words, the conductor having electrical conductivity is arranged only around the periphery of the elastic body. Therefore, the elastic body of Patent Document 1 acts as a resistance component that inhibits electrical conductivity, thereby increasing the internal resistance of the battery.

[0006] The flat nonaqueous electrolyte battery of Patent Document 2 improves sealing performance by providing a recess in the bottom wall of the positive electrode can radially inward from the sealing wall. However, the flat nonaqueous electrolyte battery of Patent Document 2 is not an all-solid-state battery, and is not intended to accommodate a power generating element formed by stacking a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. Therefore, no material is provided to absorb the pressure generated when the positive electrode can and the sealing can are crimped together, and if a power generating element were to be accommodated in the battery, there is a risk of damage such as cracking in the power generating element.

[0007] Therefore, the present disclosure provides a method for electrical contact between the outer can and the power generating element, and an electrical contact between the sealing can and the power generating element. Either one of The object of the present invention is to provide an all-solid-state battery capable of sufficiently securing a positive electrode layer or a negative electrode layer and preventing damage to the positive electrode layer or the negative electrode layer.

[0008] In order to solve the above problems, the present disclosure is configured as follows. That is, the all-solid-state battery according to the present disclosure may include an outer can having a bottom including an outwardly recessed recess and a cylindrical side wall. The all-solid-state battery may include a sealed can having a flat surface and a peripheral wall covering the opening of the outer can. The all-solid-state battery may include a power generating element disposed between the inner bottom surface of the recess of the outer can and the flat surface of the sealed can, the power generating element including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The all-solid-state battery may include a gasket crimped between the cylindrical side wall of the outer can and the peripheral wall of the sealed can. The all-solid-state battery may include at least one of a first resilient conductive sheet disposed between the inner bottom surface of the recess and the power generating element, and a second resilient conductive sheet disposed between the flat surface of the sealed can and the power generating element.

[0009] In the all-solid-state battery according to the present disclosure, electrical contact between the exterior can and the power generating element, and electrical contact between the sealing can and the power generating element are Either one of This ensures sufficient strength, and damage to the positive electrode layer or the negative electrode layer can be prevented. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing the structure of an all-solid-state battery according to this embodiment. [Figure 2] 2A to 2C are cross-sectional views illustrating a manufacturing process of the all-solid-state battery shown in FIG. [Figure 3] 3A to 3C are cross-sectional views illustrating a manufacturing process of the all-solid-state battery shown in FIG. [Figure 4] 4A to 4C are cross-sectional views illustrating a manufacturing process of the all-solid-state battery shown in FIG. [Figure 5] FIG. 5 is a cross-sectional view showing the structure of an all-solid-state battery according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] The all-solid-state battery according to this embodiment may include an outer can having a bottom including an outwardly recessed recess and a cylindrical side wall. The all-solid-state battery may include a sealed can having a flat surface and a peripheral wall, covering the opening of the outer can. The all-solid-state battery may include a power generating element disposed between the inner bottom surface of the recess of the outer can and the flat surface of the sealed can, the power generating element including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The all-solid-state battery may include a gasket crimped between the cylindrical side wall of the outer can and the peripheral wall of the sealed can. The all-solid-state battery may include a first restorable conductive sheet disposed between the power generating element and at least one of the inner bottom surface of the recess and the flat surface of the sealed can.

[0012] The first restorable conductive sheet, due to its restorability, provides electrical continuity between the exterior can and the power generating element, and electrical continuity between the sealing can and the power generating element. Either The positive electrode layer can be kept in a good condition and can also function as a buffer material, thereby mitigating the pressure generated when the outer can and the sealing can are crimped together. or This prevents damage to the negative electrode layer. Furthermore, when the first resilient conductive sheet is disposed between the inner bottom surface of the recess and the power generating element, it is positioned within the recess, preventing the first resilient conductive sheet from shifting position and being pinched between the bottom of the exterior can and the gasket when the exterior can and the sealing can are crimped together. As a result, deterioration of the sealing performance of the all-solid-state battery can be suppressed.

[0013] The first resilient conductive sheet may be disposed between the inner bottom surface of the recess and the power-generating element. The depth of the recess may be greater than the thickness of the first resilient conductive sheet. That is, the first resilient conductive sheet has a thickness smaller than the depth of the recess. This more appropriately prevents the first resilient conductive sheet from being pinched between the bottom of the outer can and the gasket when the outer can and the sealed can are crimped together.

[0014] The first resilient conductive sheet may be disposed between the inner bottom surface of the recess and the power-generating element. The all-solid-state battery may further include a second resilient conductive sheet disposed between the flat surface of the sealing can and the power-generating element. This allows for good electrical continuity between the outer can and the power-generating element, and between the sealing can and the power-generating element, and also acts as a buffer, thereby reducing the pressure generated when the outer can and the sealing can are crimped together, thereby preventing damage to the positive electrode layer and the negative electrode layer. Furthermore, because the first resilient conductive sheet is disposed between the inner bottom surface of the recess and the power-generating element, it is possible to prevent the first resilient conductive sheet from shifting position and being pinched between the bottom of the outer can and the gasket when the outer can and the sealing can are crimped together. As a result, deterioration of the sealing performance of the all-solid-state battery can be suppressed.

[0015] The depth of the recess may be smaller than the height from the inner bottom surface of the recess to the upper end of the outer circumferential surface of the solid electrolyte layer, thereby preventing contact between the bottom of the outer can and the negative electrode layer and causing a short circuit.

[0016] The first and second resilient conductive sheets may be graphite sheets.

[0017] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to Figures 1 to 4. First, as shown in Figure 1, an all-solid-state battery 1 is composed of an outer can 2, a sealing can 3, a power-generating element 4, a restorable conductive sheet 5 arranged between the outer can 2 and the power-generating element 4, a restorable conductive sheet 5 arranged between the sealing can 3 and the power-generating element 4, and a gasket 6. In this embodiment, the all-solid-state battery 1 is a flat battery.

[0018] The outer can 2 has a circular bottom 21 and a cylindrical side wall 22 formed continuously from the outer periphery of the bottom 21. The cylindrical side wall 22 is provided so as to extend substantially perpendicular to the bottom 21 in a vertical cross-sectional view. The outer can 2 is made of a metal material such as stainless steel.

[0019] The bottom 21 of the exterior can 2 has a recess 211. The recess 211 is formed integrally with the exterior can 2 by press working. The recess 211 is recessed in the axial direction outward (downward in the figure) from the bottom 21 to the all-solid-state battery 1. The recess 211 houses a restorable conductive sheet 5. The recess 211 has a depth d. As shown in FIG. 1 , the depth d of the recess 211 is the depth from the inner surface of the bottom 21 to the inner bottom surface of the recess 211. The depth d and inner diameter d1 of the recess 211 will be described in detail later.

[0020] The sealing can 3 has a circular flat portion 31 and a cylindrical peripheral wall portion 32 formed continuously from the outer periphery of the flat portion 31. The opening of the sealing can 3 faces the opening of the outer can 2. The sealing can 3 is made of a metal material such as stainless steel.

[0021] After the power generating element 4 and the restorable conductive sheet 5 are accommodated in the internal space of the outer can 2 and the sealable can 3, the outer can 2 and the sealable can 3 are crimped together with a gasket 6 interposed between the cylindrical side wall 22 of the outer can 2 and the peripheral wall 32 of the sealable can 3. Specifically, the outer can 2 and the sealable can 3 are arranged with their openings facing each other, the peripheral wall 32 of the sealable can 3 is inserted inside the cylindrical side wall 22 of the outer can 2, and then the outer can 2 and the sealable can 3 are crimped together with the gasket 6 interposed between the cylindrical side wall 22 and the peripheral wall 32. As a result, the internal space formed by the outer can 2 and the sealable can 3 is sealed. The configurations, materials, shapes, etc. of the outer can 2, the sealable can 3, and the gasket 6 are not particularly limited.

[0022] The power generating element 4 includes a positive electrode layer 41, a negative electrode layer 42, and a solid electrolyte layer 43. The solid electrolyte layer 43 is disposed between the positive electrode layer 41 and the negative electrode layer 42. The power generating element 4 is stacked in the order of the positive electrode layer 41, the solid electrolyte layer 43, and the negative electrode layer 42 from the bottom 21 side (bottom in the figure) of the outer can 2. The power generating element 4 is formed in a cylindrical shape. The power generating element 4 is disposed on the inner bottom surface of the recess 211 of the outer can 2 via a restorable conductive sheet 5. Therefore, the outer can 2 functions as a positive electrode can. Furthermore, the power generating element 4 is in contact with the inner surface of the flat portion 31 of the sealing can 3 via the restorable conductive sheet 5. Therefore, the sealing can 3 functions as a negative electrode can. The shape of the power generating element 4 is not limited to a cylindrical shape, and can be variously modified, such as a rectangular parallelepiped shape or a polygonal prism shape, depending on the shape of the all-solid-state battery 1.

[0023] The positive electrode layer 41 is made of LiNi particles having an average particle size of 3 μm, which is a positive electrode active material used in lithium ion secondary batteries. 0.6 Co 0.2 Mn 0.2 The positive electrode pellet is formed into a cylindrical shape by placing 180 mg of a positive electrode mixture containing O2, a sulfide solid electrolyte (Li6PS5Cl), and carbon nanotubes as a conductive additive in a mass ratio of 55:40:5 in a mold with a diameter of 10 mm. The positive electrode layer 41 is not particularly limited as long as it can function as the positive electrode layer of the power generating element 4. For example, the positive electrode layer 41 may be lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese composite oxide, olivine-type composite oxide, or an appropriate mixture of these. The size and shape of the positive electrode layer 41 are not limited to a cylindrical shape and can be variously changed depending on the size and shape of the all-solid-state battery 1.

[0024] The negative electrode layer 42 is made of LTO (Li4Ti5O 12The negative electrode pellet is a cylindrically shaped negative electrode pellet containing 300 mg of a negative electrode mixture containing lithium ion battery (Li6PS5Cl), a sulfide solid electrolyte (Li6PS5Cl), and carbon nanotubes in a weight ratio of 50:45:5. The negative electrode layer 42 is not particularly limited as long as it can function as the negative electrode layer of the power generating element 4. For example, it can be made of metallic lithium, a lithium alloy, graphite, a carbon material such as low-crystalline carbon, SiO, LTO (Li4Ti5O 12 , lithium titanate), etc., or an appropriate mixture of these. The size and shape of the negative electrode layer 42 are not limited to a cylindrical shape, and can be variously changed depending on the size and shape of the all-solid-state battery 1.

[0025] The solid electrolyte layer 43 is formed by molding 60 mg of a sulfide solid electrolyte (LiPSCl) into a cylindrical shape. The solid electrolyte layer 43 is not particularly limited, but may be a sulfur-based solid electrolyte such as an argyrodite-type solid electrolyte in terms of ion conductivity. When a sulfur-based solid electrolyte is used, it is preferable to coat the surface of the positive electrode active material with niobium oxide (LiNbO, etc.) to prevent reaction with the positive electrode active material. The solid electrolyte layer 43 may also be a hydride-based solid electrolyte, an oxide-based solid electrolyte, or the like. The size and shape of the solid electrolyte layer 43 are not limited to a cylindrical shape and can be variously changed depending on the size and shape of the all-solid-state battery 1.

[0026] The resilient conductive sheet 5 is a sheet made of a conductive material that generates a certain repulsive force when it attempts to restore its shape when compressed to a reduced thickness. The sheet constituting the resilient conductive sheet 5 is preferably made of an elastic material that is elastically deformable, such as conductive rubber made by uniformly mixing carbon black or metal powder with rubber to provide conductivity. Materials that do not completely return to their original shape when compression is stopped, but partially restore their thickness at a predetermined rate, such as graphite sheets, are also preferably used. The resilient conductive sheets 5 are disposed between the recess 211 of the outer can 2 and the positive electrode layer 41 of the power-generating element 4, and between the flat portion 31 of the sealing can 3 and the negative electrode layer 42 of the power-generating element 4. That is, the resilient conductive sheets 5 are disposed on both the upper and lower surfaces of the power-generating element 4. The planar shape of the resilient conductive sheet 5 is formed to be substantially similar to the planar shape of the internal space of the all-solid-state battery 1. Therefore, the resilient conductive sheet 5 is formed to be substantially circular in plan view. The area of ​​the upper surface of the restorable conductive sheet 5 on the outer can 2 side may be the same as the area of ​​the lower surface of the positive electrode layer 41 of the power generating element 4, or may be slightly different from the area of ​​the lower surface of the positive electrode layer 41 of the power generating element 4. The area of ​​the lower surface of the restorable conductive sheet 5 on the sealing can 3 side may be the same as the area of ​​the upper surface of the negative electrode layer 42 of the power generating element 4, or may be slightly different from the area of ​​the upper surface of the negative electrode layer 42 of the power generating element 4. The upper surface of the restorable conductive sheet 5 on the outer can 2 side preferably covers the lower surface of the positive electrode layer 41, and the lower surface of the restorable conductive sheet 5 on the sealing can 3 side preferably covers the upper surface of the negative electrode layer 42. The restorable conductive sheet 5 is pressed together with the power generating element 4 by crimping during battery assembly, and the battery assembly is completed in a state where the restorable conductive sheet 5 is compressed in the thickness direction (the vertical direction in FIG. 1 ), and functions as a current collecting sheet. When the assembled all-solid-state battery 1 is charged and discharged, the power-generating element 4 repeatedly expands and contracts, but the restorable conductive sheet 5 is maintained in a compressed state, and therefore, by continuing to press the power-generating element 4 with a repulsive force, it is possible to continue to maintain good electrical continuity between the outer can 2 and the power-generating element 4, and between the sealing can 3 and the power-generating element 4.Furthermore, by disposing the restorable conductive sheet 5 between the recess 211 of the exterior can 2 and the positive electrode layer 41 of the power-generating element 4, there is no risk of the restorable conductive sheet 5 being misaligned and being pinched between the bottom 21 of the exterior can 2 and the gasket 6 when the exterior can 2 and the sealing can 3 are crimped together, thereby suppressing a decrease in sealing performance due to this. Furthermore, contact between the positive electrode layer 41 and the peripheral edge of the inner bottom surface of the recess 211 can be prevented, and damage to the positive electrode layer 41 can be prevented.

[0027] The shape of the restorable conductive sheet 5 is not limited to a substantially circular shape in plan view, and may be variously changed, such as an elliptical shape or a substantially polygonal shape in plan view, depending on the shape of the all-solid-state battery 1 in plan view. Furthermore, the restorable conductive sheet 5 does not have to be disposed between the power generating element 4 and both the inner bottom surface of the recess 211 of the outer can 2 and the flat surface 31 of the sealing can 3, but may be disposed only between the power generating element 4 and the inner bottom surface of the recess 211 of the outer can 2, or only between the power generating element 4 and the flat surface 31 of the sealing can 3, and the repulsive force continues to press the power generating element 4, thereby maintaining electrical continuity between the outer can 2 and the power generating element 4, and between the sealing can 3 and the power generating element 4. Either On the other hand, since the peripheral edge of the flat surface portion 31 of the sealing can 3 is easily deformed by the force applied during crimping, if the restorable conductive sheet 5 is placed at least on the side of the flat surface portion 31 of the sealing can 3, this acts as a buffer material and can prevent damage to the negative electrode layer 42.

[0028] The resilient conductive sheet 5 may be a graphite sheet, as described above. The graphite sheet is formed by rolling expanded graphite, and more specifically, is produced as follows. First, particles of acid-treated graphite, which is natural graphite that has been treated with an acid, are heated. The acid present between the layers of the acid-treated graphite then vaporizes and foams, causing it to expand. This expanded graphite (expanded graphite) is molded into a felt shape and further rolled using a rolling mill to form a sheet. The graphite sheet is produced by cutting out a circular shape from the expanded graphite sheet. As described above, expanded graphite is formed by vaporizing the acid and foaming the acid-treated graphite. Therefore, the graphite sheet is formed into a porous sheet. Therefore, the graphite sheet has excellent flexibility and resilience due to its porosity, in addition to the conductivity of graphite itself. As a result, the graphite sheet functions as a current collector and can suppress damage and deterioration of the conductivity of the power generating element 4, which expands and contracts during charging and discharging. The graphite sheet may be manufactured by any method other than the above. Also, the restorable conductive sheet 5 is not limited to a graphite sheet, and may be made of a conductive tape.

[0029] Here, the depth d and inner diameter d1 of the recess 211 will be described in detail. As shown in FIG. 1 , the depth d of the recess 211 is larger than the thickness t of the resilient conductive sheet 5. Furthermore, the inner diameter of the recess 211 is larger than the outer diameter of the resilient conductive sheet 5. In other words, the entire resilient conductive sheet 5 is accommodated in the internal space of the recess 211. This prevents the resilient conductive sheet 5 from being pinched between the bottom 21 of the outer can 2 and the gasket 6 when the outer can 2 and the sealing can 3 are crimped together. As a result, the current collection efficiency of the resilient conductive sheet 5 can be improved.

[0030] If the thickness t of the resilient conductive sheet 5 is too thick, the proportion of the power generating element 4 in the internal space of the all-solid-state battery 1 will decrease, resulting in a smaller battery capacity. Therefore, the ratio A(t / d) of the depth d of the recess 211 to the resilient conductive sheet 5 is preferably less than 1.0, preferably 0.9 or less, and more preferably 0.8 or less. On the other hand, if the resilient conductive sheet 5 is too thin, the effects of preventing damage and a decrease in conductivity when the power generating element 4 expands and contracts will decrease. Therefore, the ratio A(t / d) of the depth d of the recess 211 to the resilient conductive sheet 5 is preferably 0.5 or more, preferably 0.6 or more, and more preferably 0.7 or more.

[0031] More specifically, when the resilient conductive sheet 5 is a graphite sheet, the thickness t of the resilient conductive sheet 5 (graphite sheet) is preferably 0.05 mm or more, more preferably 0.07 mm or more, and is preferably 0.5 mm or less, more preferably 0.2 mm or less, from the viewpoints of improving the proportion of the power generating element 4 occupying the internal space of the all-solid-state battery 1, i.e., improving the battery capacity of the power generating element 4, and preventing damage and a decrease in conductivity when the power generating element 4 expands and contracts. Note that the thickness t of the resilient conductive sheet 5 (graphite sheet) is not limited to a graphite sheet, and can also be applied to a resilient conductive sheet 5 formed from other materials such as conductive tape.

[0032] The apparent density of the restorable conductive sheet 5 (graphite sheet) is 0.3 g / cm 3 More preferably, 0.7 g / cm 3 or more, 1.5 g / cm 3 Preferably, it is equal to or less than 1.3 g / cm 3 It is preferable to set the apparent density below 1 / 2. If the apparent density is too low, the resilient conductive sheet 5 (graphite sheet) becomes more susceptible to breakage, and if the apparent density is too high, flexibility decreases. Note that the apparent density of the resilient conductive sheet 5 (graphite sheet) is not limited to graphite sheets, and can also be applied to resilient conductive sheets 5 formed from other materials such as conductive tape.

[0033] Furthermore, the recovery rate of the recoverable conductive sheet 5 (graphite sheet) is preferably 7% or more. The recoverable conductive sheet 5 (graphite sheet) has such an appropriate recovery rate, so that the recoverable conductive sheet 5 (graphite sheet) applies an appropriate amount of pressure to the power-generating element 4. This allows good electrical continuity to be maintained between the inner bottom surface of the recess 211 of the outer can 2 and the power-generating element 4, and good electrical continuity to be maintained between the inner surface of the flat portion 31 of the sealed can 3 and the power-generating element 4. From the viewpoint of maintaining good electrical continuity, the recovery rate is more preferably 10% or more. On the other hand, from the viewpoint of reducing the pressure on the power-generating element 4 that occurs when the outer can 2 and the sealed can 3 are crimped together, the recovery rate is preferably 80% or less, more preferably 50% or less, and particularly preferably 30% or less. The recovery rate is expressed by the following formula, where t is the thickness of the recoverable conductive sheet 5 (graphite sheet), t1 is the thickness of the recoverable conductive sheet 5 (graphite sheet) when compressed with a predetermined pressure, and t2 is the thickness of the recoverable conductive sheet 5 (graphite sheet) when the pressure is removed. Furthermore, a recoverable conductive sheet 5 (graphite sheet) is considered to have recovery when its recovery rate is equal to or greater than a certain level. (t2-t1) / (t-t1)×100(%) The recovery rate can be measured by the method described in Japanese Industrial Standard JIS R3453 2001 (joint sheet). Note that the recovery rate of the recoverable conductive sheet 5 (graphite sheet) is not limited to graphite sheets, but can also be applied to recoverable conductive sheets 5 formed from other materials such as conductive tape.

[0034] Therefore, it is preferable that the apparent density or thickness of the resilient conductive sheet 5 (graphite sheet) be determined in a balanced manner, taking into consideration flexibility, resilience, and effective use of the internal space.

[0035] As described above, the restorable conductive sheet 5 (graphite sheet) has excellent conductivity and flexibility. Therefore, the restorable conductive sheet 5 (graphite sheet) can function as a current collector and can absorb expansion and contraction due to charge and discharge of the power generating element 4, or the pressing force when the outer can 2 and the sealing can 3 are crimped together. This makes it possible for the all-solid-state battery 1 to suppress deterioration of battery performance due to damage to the power generating element 4 or the formation of gaps.

[0036] Furthermore, as described above, the highly flexible restorable conductive sheet 5 (graphite sheet) has adequate restorability to expansion caused by charging of the power generating element 4 or compression caused by the pressing force when crimping the exterior can 2 and the sealing can 3. This allows the all-solid-state battery 1 to maintain good electrical continuity between the inner surface of the bottom 21 of the exterior can 2 and the power generating element 4, and to maintain good electrical continuity between the inner surface of the flat part 31 of the sealing can 3 and the power generating element 4, thereby maintaining battery performance.

[0037] As shown in FIG. 1 , the depth d of the recess 211 is smaller than the height h. The height h is the height from the inner bottom surface of the recess 211 to the upper end of the outer circumferential surface of the solid electrolyte layer 43. In other words, the height h is the total height of the positive electrode layer 41 and the solid electrolyte layer 43. This makes it possible to prevent the bottom 21 of the outer can 2 from coming into contact with the negative electrode layer 42 and causing a short circuit. Note that when the positions of the positive electrode layer 41 and the negative electrode layer 42 are interchanged, the height h is the total height of the negative electrode layer 42 and the solid electrolyte layer 43.

[0038] The outer diameter d2 of the restorable conductive sheet 5 is smaller than the inner diameter d1 of the recess 211 so that the restorable conductive sheet 5 can be accommodated within the recess 211. If the outer diameter d2 of the restorable conductive sheet 5 is too large relative to the inner diameter d1 of the recess 211, it becomes difficult to accommodate the restorable conductive sheet 5 within the recess 211. Therefore, the ratio C (d1 / d2) of the inner diameter d1 of the recess 211 to the outer diameter d2 of the restorable conductive sheet 5 is preferably 1.02 or greater, more preferably 1.05 or greater, and even more preferably 1.08 or greater. On the other hand, if the outer diameter d2 of the restorable conductive sheet 5 is too small relative to the inner diameter d1 of the recess 211, the contact area between the outer diameter d2 of the restorable conductive sheet 5 and the power-generating element 4 becomes smaller, resulting in a decrease in the current collection efficiency of the restorable conductive sheet 5. Therefore, the ratio C (d1 / d2) is preferably 1.15 or less, more preferably 1.12 or less, and even more preferably 1.09 or less. The inner diameter d1 of the recess 211 is smaller than the outer diameter of the positive electrode layer 41 of the power generating element 4. This is because the end of the power generating element 4 on the positive electrode layer 41 side is accommodated in the recess 211, as shown in FIG.

[0039] Next, a method for manufacturing the all-solid-state battery 1 will be described. As shown in Fig. 2, a restorable conductive sheet 5 is placed in the recess 211 of the outer can 2. Then, the power generating element 4 is placed on the upper surface of this restorable conductive sheet 5, and then another restorable conductive sheet 5 is placed on the upper surface of the power generating element 4.

[0040] Next, as shown in Fig. 3, a gasket 6 is formed on the peripheral edge of the peripheral wall portion 32 of the sealable can 3. The gasket 6 is formed from the inner surface of the peripheral wall portion 32, passing around the peripheral edge of the peripheral wall portion 32, and extending to the outside of the peripheral wall portion 32. There are no particular limitations on the method for forming the gasket 6, but injection molding or the like is commonly used.

[0041] Next, as shown in FIG. 4, the sealing can 3 is placed so as to cover the opening of the outer can 2. At this time, the gasket 6 comes into contact with the inner surface of the bottom 21 of the outer can 2 and therefore does not penetrate into the recess 211. On the other hand, the restorable conductive sheet 5 is housed in the recess 211 of the outer can 2, which prevents the restorable conductive sheet 5 from being pinched between the inner surface of the bottom 21 of the outer can 2 and the gasket 6. Finally, the tip of the gasket 6 formed on the outside of the peripheral wall 32 is pressed, together with the cylindrical side wall 22 of the outer can 2, toward the outer peripheral surface of the peripheral wall 32 of the sealing can 3. As a result, the outer can 2 and the sealing can 3 are crimped together, and the all-solid-state battery 1 shown in FIG. 1 is completed.

[0042] 1 assembled using a graphite sheet (resilient conductive sheet 5) can prevent damage to the positive electrode layer 41 and the negative electrode layer 42 due to the resilience of the graphite sheet. Furthermore, this all-solid-state battery 1 has excellent sealing properties because it can prevent the graphite sheet from being sandwiched between the inner surface of the bottom 21 of the outer can 2 and the gasket 6. Therefore, when the all-solid-state battery 1 is charged and discharged, a predetermined discharge capacity can be obtained.

[0043] Here, cycle tests were carried out on the all-solid-state battery 1 shown in FIG. 1, which uses a graphite sheet as the recoverable conductive sheet 5, and on an all-solid-state battery having the same configuration as the all-solid-state battery 1 shown in FIG. 1 except that the bottom of the outer can is flat and has no recesses. The recoverable conductive sheet 5 has a thickness of 0.1 mm and an apparent density of 1.2 g / cm. 3 A graphite sheet with a recovery rate of 12% was used. The former all-solid-state battery 1 can maintain good electrical continuity between the outer can 2 and the sealing can 3 and the power generating element 4 when the charge-discharge cycle is repeated, and therefore, even after 100 cycles, it was possible to maintain a discharge capacity of 95% or more of that before the charge-discharge cycle was repeated.

[0044] On the other hand, in the latter all-solid-state battery, the position of the graphite sheet was shifted in some of the test specimens, which reduced the sealing performance and allowed moisture from the air to get in, resulting in a deterioration in the battery characteristics. As a result, some of the latter all-solid-state batteries did not reach the specified discharge capacity.

[0045] In addition, a similar cycle test was also performed on an all-solid-state battery having the same configuration as the all-solid-state battery 1 shown in FIG. 1, except that a 1 mm thick, 97% porosity metal foam substrate (external can side: made of aluminum, sealing can side: made of copper) was used instead of the resilient conductive sheet 5 (graphite sheet). The foam substrate of this all-solid-state battery is a current collector that does not have substantial resilience, and therefore is unable to maintain good electrical continuity between the external can and sealing can and the power generating element. As a result, the discharge capacity of this all-solid-state battery after 100 cycles decreased to about 10% of that before repeated charge-discharge cycles.

[0046] (Variation) In the all-solid-state battery 1 of the above embodiment, the restorable conductive sheet 5 is provided between the power generating element 4 and the inner bottom surface of the recess 211 of the outer can 2, and the restorable conductive sheet 5 is provided between the power generating element 4 and the inner surface of the flat portion 31 of the sealing can 3, but the restorable conductive sheet 5 can also be provided only between the power generating element 4 and the inner surface of the flat portion 31 of the sealing can 3.

[0047] 5, the peripheral wall portion 32 of the sealing can 3 may be composed of a base end portion 32a, an expanded diameter portion 32b, and a step portion 32c. The base end portion 32a is provided so as to extend substantially perpendicular to the flat portion 31 in a vertical cross-sectional view. The expanded diameter portion 32b is provided in a stepped shape via the step portion 32c so that its diameter is larger than that of the base end portion 32a. In other words, the step portion 32c is provided between the base end portion 32a and the expanded diameter portion 32b. The open end of the cylindrical side wall portion 22 of the outer can 2 is bent toward the step portion 22c and crimped. This allows the outer can 2 and the sealing can 3 to be sufficiently crimped together, and the diameter of the flat portion 31 of the sealing can 3 can be made larger than that of the all-solid-state battery 1 of the above-mentioned embodiment. 5 can effectively utilize the internal space of the all-solid-state battery 1 when it has the same diameter as the all-solid-state battery 1 of the above-described embodiment, or can reduce the size of the all-solid-state battery 1 when a power generating element 4 having the same diameter as the all-solid-state battery 1 of the above-described embodiment is accommodated in the internal space. In the all-solid-state battery 1 shown in FIG. 5, the peripheral wall portion 32 of the sealing can 3 is bent at the opening end so that the expanded diameter portion 32b forms a double wall, but the expanded diameter portion 32b can also be formed as a straight wall without being bent, that is, the tip of the peripheral wall portion 32 can be formed so as to face the bottom portion 21 of the outer can 2.

[0048] Although the embodiments have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure. [Explanation of symbols]

[0049] 1 All-solid-state battery 2 outer can, 21 bottom, 211 recess, 22 cylindrical side wall 3 Sealing can, 31 Plane section, 32 Surrounding wall section 4 power generating element, 41 positive electrode layer, 42 negative electrode layer, 43 solid electrolyte layer 5. Resilient conductive sheet 6 gaskets

Claims

1. an outer can having a bottom portion including an outwardly recessed recess and a cylindrical side wall portion; a sealing can having a flat portion and a peripheral wall portion and covering an opening of the outer can; a power generating element disposed between the inner bottom surface of the recessed portion of the exterior can and the flat surface of the sealing can, the power generating element having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; a gasket that is crimped between the cylindrical side wall portion of the outer can and the peripheral wall portion of the sealed can; a first restorable conductive sheet disposed between the power generating element and at least one of an inner bottom surface of the recess and a flat surface of the sealing can, The all-solid-state battery, wherein the first resilient conductive sheet is a graphite sheet.

2. The all-solid-state battery according to claim 1, the first resilient conductive sheet is disposed between the inner bottom surface of the recess and the power generating element; a depth of the recess is greater than a thickness of the first resilient conductive sheet.

3. The all-solid-state battery according to claim 1 or 2, the first resilient conductive sheet is disposed between the inner bottom surface of the recess and the power generating element; The all-solid-state battery further comprises: a second restorable conductive sheet disposed between the flat surface of the sealing can and the power generating element; The all-solid-state battery, wherein the second resilient conductive sheet is a graphite sheet.

4. The all-solid-state battery according to any one of claims 1 to 3, a depth of the recess is smaller than a height from an inner bottom surface of the recess to an upper end of an outer peripheral surface of the solid electrolyte layer.

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