All-solid-state batteries

Abstract

To suppress overcharge with no special structure being disposed outside an outer package.SOLUTION: An all-solid-state battery comprises: a laminated body in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated; and an outer package configured to enclose and seal the laminated body and being capable of following deformation in a lamination direction of the laminated body. The all-solid-state battery further comprises an overcharge suppression part configured to be enclosed and sealed in the outer package together with the laminated body and be capable of short-circuiting a positive electrode collector of the positive electrode layer and a negative electrode collector of the negative electrode layer. The overcharge suppression part includes: a first conductor extending from one of the positive electrode collector and the negative electrode collector; and a second conductor extending from another of the positive electrode collector and the negative electrode collector and separated from the first conductor. The first conductor and the second conductor are conducted in accordance with a state change of the laminated body.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery. [Background technology]

[0002] In order to reduce CO2 emissions in light of climate-related disasters, the electrification of industrial machinery is being promoted, and research is being conducted on secondary batteries as an energy source for vehicles and other applications. Secondary batteries can expand and generate heat when overcharged. To address this issue, for example, secondary batteries with a structure that discharges when overcharged have been proposed. Patent Document 1 discloses a liquid secondary battery in which the electrode layers and other components are enclosed and sealed in an exterior housing, and which has a structure that shorts the positive and negative electrodes to the outside of the exterior housing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-110959 Summary of the Invention [Problem to be solved by the invention]

[0004] The discharge structure of Patent Document 1 is located outside the exterior body and is exposed, so care must be taken when handling it not to damage the discharge structure, and when using the secondary battery of Patent Document 1 as a battery pack, assembly, etc. may be time-consuming.

[0005] An object of the present invention is to provide an all-solid-state battery that can suppress overcharging without providing a special structure on the outside of an exterior body. [Means for solving the problem]

[0006] According to the present invention, a laminate formed by stacking a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; an exterior body that surrounds and seals the laminate and is capable of following deformation of the laminate in the stacking direction; An all-solid-state battery comprising: an overcharge prevention unit that is enclosed and sealed together with the laminate in the exterior body and that can short-circuit a positive electrode current collector of the positive electrode layer and a negative electrode current collector of the negative electrode layer; The overcharge prevention unit is a first conductor extending from one of the positive electrode current collector and the negative electrode current collector; a second conductor extending from the other of the positive electrode current collector and the negative electrode current collector and spaced apart from the first conductor, the first conductor includes a portion laminated on the laminate; The expansion of the laminate in the stacking direction brings the first conductor and the second conductor into contact with each other, thereby establishing electrical conduction therebetween. An all-solid-state battery characterized by the above structure is provided. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an all-solid-state battery that can suppress overcharging without providing a special structure on the outside of the exterior housing. [Brief explanation of the drawings]

[0008] [Figure 1] 1A is a plan view of an all-solid-state battery according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A. [Figure 2] 1A is a cross-sectional view taken along line BB in FIG. 1A, and FIG. 1B is a diagram showing the function of the overcharge prevention unit. [Figure 3] 10A and 10B are diagrams showing another example of the configuration of the overcharge prevention unit. [Figure 4] 10A and 10B are diagrams showing another example of the configuration of the overcharge prevention unit. [Figure 5] 1A is a diagram showing another example of the configuration of the overcharge prevention unit, and FIG. 1B is a diagram showing an example of the characteristics of an NTC thermistor. [Figure 6] 10A and 10B are diagrams showing other examples of the arrangement of the overcharge prevention unit. [Figure 7] 10A and 10B are diagrams showing another example of the configuration of the overcharge prevention unit. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be arbitrarily combined. Furthermore, the same reference numerals are used for the same or similar components, and redundant explanations will be omitted.

[0010] First Embodiment Fig. 1(A) is a plan view of an all-solid-state battery 1 according to one embodiment of the present invention, and (B) is a cross-sectional view taken along line AA in Fig. 1(A). In the figure, arrow X indicates the longitudinal direction of the all-solid-state battery 1 (or the direction in which the lead tabs extend), arrow Y indicates the width direction of the all-solid-state battery 1 (or the direction perpendicular to the direction in which the lead tabs extend), and arrow Z indicates the thickness direction of the all-solid-state battery 1 (the stacking direction of the laminate 2), with the X direction, Y direction, and Z direction being perpendicular to one another. Fig. 1(A) is a view of the all-solid-state battery 1 viewed in the Z direction.

[0011] The all-solid-state battery 1 includes a laminate 2 which is an electricity storage element, an exterior body 8 which surrounds and seals the laminate 2, lead tabs 3 and 4, current collecting tabs 5 and 6, and an overcharge prevention unit 7, and has the form of a battery cell suitable for an assembled battery.

[0012] The laminate 2 has a rectangular parallelepiped shape as a whole and has a two-layer structure of positive electrode layers 21A and 21B and two negative electrode layers 24A and 24B. However, the positive electrode layer and the negative electrode layer of the laminate 2 may be one layer, or three or more layers. A solid electrolyte layer 27 is provided between the positive electrode layer 21A and the negative electrode layer 24A, and between the positive electrode layer 21B and the negative electrode layer 24B.

[0013] The positive electrode layers 21A and 21B each include a positive electrode active material layer 22, and the two positive electrode layers 21A and 21B share a positive electrode current collector 23. The positive electrode current collector 23 is arranged in a layered form at the center of the stack 2 in the Z direction, and the positive electrode active material layers 22 are stacked on the front and back sides thereof.

[0014] The negative electrode layers 24A and 24B are disposed on one side of the positive electrode layers 21A and 24B in the Z direction, and are stacked such that the positive electrode layers 21A and 24B are sandwiched between the negative electrode layers 24A and 24B. However, a configuration opposite to the configuration of this embodiment, in which two positive electrode layers sandwich two negative electrode layers, may also be employed. The negative electrode layers 24A and 24B each include a negative electrode active material layer 25 and a negative electrode current collector 26. The two negative electrode current collectors 26 are each formed as a layer on the outermost layer of the laminate 2.

[0015] Examples of active materials constituting the positive electrode active material layer 22 include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium metal phosphate. Examples of active materials constituting the negative electrode active material layer 26 include lithium-based materials and silicon-based materials. Examples of lithium-based materials include Li metal and Li alloys. Examples of silicon-based materials include Si and SiO. Other active materials constituting the negative electrode active material layer 25 include carbon materials such as graphite, soft carbon, and hard carbon, as well as tin-based materials (Sn, SnO, etc.) and lithium titanate, which are materials with relatively large volume expansion.

[0016] The solid electrolyte layer 27 is made of, for example, a solid electrolyte having ion conductivity, and examples of such materials include a sulfide-based solid electrolyte material, an oxide-based solid electrolyte material, a nitride-based solid electrolyte material, and a halide-based solid electrolyte material. The positive electrode current collector 23 and the negative electrode current collector 26 are made of, for example, a metal foil, a metal sheet, or a metal plate made of aluminum, copper, SUS, or the like. The positive electrode active material layer 22, the negative electrode active material layer 25, and the solid electrolyte layer 27 may be formed by binding particles of the materials that make them up with an organic polymer compound binder.

[0017] When viewed in the Z direction, the exterior body 8 has a rectangular shape with four sides 8a to 8d, a cup-shaped recess 80 in the center, and a sealing portion 81 on the periphery. The exterior body 8 is formed by folding a single sheet of material in two, or by bonding two sheets of material together. The material is formed, for example, by covering the front and back surfaces of a metal layer with a resin layer (insulating layer), and the exterior body 8 has flexibility that allows it to follow the expansion and contraction of the laminate 2. The flexibility that allows it to follow the expansion and contraction of the laminate 2 can be obtained by the properties of the material of the exterior body 8 and the shape of the exterior body 8.

[0018] The recesses 80 are formed on both sides in the Z direction so as to accommodate the laminate 2, and a rectangular parallelepiped accommodation space is formed by this pair of recesses 80. This accommodation space is also referred to as the interior of the exterior body 8. The sealing portion 81 is formed by bonding the materials of the exterior body 8 together by adhesive bonding, welding, or the like. Of the four sides 8a to 8d, the opposing sides 8a and 8b are provided with strip-shaped lead tabs 3 and 4 that traverse the sealing portion 81, and the laminate 2 is located between the lead tabs 3 and 4. The laminate 2 can be charged or discharged by connecting the lead tabs 3 and 4 to a charger or an electrical load.

[0019] One end of the lead tab 3 is located outside the exterior body 8, and the other end is located inside the exterior body 8. The other end of the lead tab 3 is connected to the positive electrode current collector 23 inside the exterior body 8 via a current collecting tab 5, and the lead tab 3 forms a tab for the positive electrode. The lead tab 3 and the current collecting tab 5 are formed, for example, from a conductive metal sheet or metal plate.

[0020] One end of the lead tab 4 is located outside the exterior body 8, and the other end is located inside the exterior body 8. The other end of the lead tab 4 is connected to the negative electrode current collector 26 inside the exterior body 8 via a current collecting tab 6, and the lead tab 4 forms a tab for the negative electrode. The lead tab 4 and the current collecting tab 6 are formed, for example, from a conductive metal sheet or metal plate.

[0021] The overcharge prevention unit 7 is disposed inside the exterior body 8, and is disposed in particular by utilizing the empty space between the laminate 2 and the side 8a. Fig. 2(A) is a cross-sectional view of the overcharge prevention unit 7 taken along line BB in Fig. 1(A).

[0022] The overcharge prevention unit 7 short-circuits the positive electrode current collector 23 and the negative electrode current collector 26 due to a change in state of the laminate 2, causing self-discharge of the laminate 2 and suppressing overcharging of the laminate 2. In this embodiment, the state change of the laminate 2 is achieved by utilizing the expansion of the laminate 2 in the Z direction to short-circuit the positive electrode current collector 23 and the negative electrode current collector 26. The overcharge prevention unit 7 is provided independently of the lead tabs 3 and 4 and the current collecting tabs 5 and 6.

[0023] The overcharge prevention unit 7 includes a conductor 70 extending from the positive electrode current collector 23 and a conductor 72 extending from each negative electrode current collector 26. The conductors 70 and 72 are formed, for example, from conductive metal plates. The conductor 70 is formed integrally with the positive electrode current collector 23, or is prepared as a separate member from the positive electrode current collector 23 and joined to the positive electrode current collector 23. Similarly, each conductor 72 is formed integrally with the negative electrode current collector 26, or is prepared as a separate member from the negative electrode current collector 26 and joined to the negative electrode current collector 26.

[0024] The conductor 70 includes an extension portion 70a extending from an end of the positive electrode current collector 23 in a direction away from the laminate 2 in the X direction, and a pair of extension portions 70b bent 90 degrees from the extension portion 70a and extending in a direction away from the extension portion 70a in the Z direction. The conductor 70 further includes an extension portion 70c bent 90 degrees from each extension portion 70b and extending in a direction approaching the laminate 2 in the X direction, and an extension portion 70d bent 90 degrees from the extension portion 70c and extending in a direction approaching the extension portion 70a in the Z direction.

[0025] The extensions 70a to 70d have a C-shaped cross section (XZ cross section), and the conductor 70 has two C-shaped portions corresponding to the two conductors 72. The outer surfaces of the extensions 70b to 70d are covered with an insulating layer 71 made of an insulating material such as resin, which prevents conduction between the conductors 70 and 72 due to unintentional contact.

[0026] Each conductor 72 includes an extension portion 72a that extends obliquely from the end of the negative electrode current collector 26 toward the extension portion 70a, and an end portion 72b that is bent from the extension portion 72a and extends in the X direction away from the laminate 2. The end portion 72b is inserted between the extension portion 70a and the extension portion 70c. A support member 73 is provided between the extension portion 70a and the extension portion 70c so as to fill the gap therebetween. The support member 73 is formed, for example, from an elastically deformable resin, and supports the end portion 72b.

[0027] The tip of extension portion 70d and end portion 72b form electrical contact portions between conductors 70 and 72, respectively, and are positioned so that the tip of extension portion 70d faces end portion 72b, which has a flat surface.

[0028] The operation of the overcharge prevention unit 7 having such a configuration will be described with reference to Figures 2(A) and 2(B). When charging and discharging of the laminate 2 is performed properly, as shown in Figure 2(A), the extension portion 70d and the end portion 72b are separated and not in contact with each other, and there is no electrical continuity between the conductor 70 and the conductor 72. In other words, there is no short circuit between the positive electrode current collector 23 and the negative electrode current collector 26.

[0029] On the other hand, when the laminate 2 is charged and becomes overcharged, the laminate 2 expands in the Z direction, and the exterior body 8 follows this deformation. Due to this expansion, as shown in FIG. 2(B), the conductor 72 is displaced outward in the Z direction as indicated by the solid arrow in FIG. 2(B), resulting in contact between the tip of the extension portion 70d and the end portion 72b. Because the end portion 72b has a flat surface, when the laminate 2 expands, the tip of the extension portion 70d more reliably contacts the end portion 72b. Note that the example in FIG. 2(B) illustrates a case where the negative electrode layer 24A expands.

[0030] The contact between the tip of the extension portion 70d and the end portion 72b establishes electrical continuity between the conductor 70 and the conductor 72. As a result, the positive electrode current collector 23 and the negative electrode current collector 26 are short-circuited, causing self-discharge (the dashed arrow in FIG. 2(B) illustrates the direction of current flow). As a result, overcharging of the laminate 2 is suppressed.

[0031] When charging of the laminate 2 ends and power is discharged to the electrical load, the expanded negative electrode layer 24A contracts to its original size. This causes the overcharge prevention unit 7 to return to the state shown in FIG. 2(A), and the extension portion 70d and the end portion 72b are again separated and no longer in contact with each other. This results in no electrical conduction between the conductor 70 and the conductor 72, and no short circuit between the positive electrode current collector 23 and the negative electrode current collector 26.

[0032] That is, in the overcharge prevention unit 7, the conductors 70 and 72 reversibly come into contact with each other due to the expansion of the laminate 2 in the Z direction, and come into a non-contact state when the laminate 2 contracts. Therefore, even if the laminate 2 temporarily falls into an overcharged state, the laminate 2 can be used continuously.

[0033] As described above, in this embodiment, the overcharge prevention unit 7 is disposed inside the exterior body 8, making it possible to provide an all-solid-state battery that can prevent overcharge without providing a special structure on the exterior body. The overcharge prevention unit 7 prevents overcharge by contact between the conductor 70 and the conductor 72 when the laminate 2 expands. Unlike liquid-based secondary batteries, there is no liquid inside the exterior body 8 of the all-solid-state battery 1. Therefore, the contact and separation between the conductor 70 and the conductor 72 inside the exterior body 8 can be utilized to more reliably short-circuit and release the short circuit between the positive electrode current collector 23 and the negative electrode current collector 26.

[0034] Furthermore, end 72b forming the electrical contact portion is arranged so as to be surrounded by extensions 70a to 70c, and contact and separation between end 72b and extension 72d are performed in a narrow area. By limiting the area of ​​the electrical contact portion, conductors 70 and 72 can be more stably contacted and separated.

[0035] Furthermore, since the conductors 72 are provided corresponding to the negative electrode layers 24A and 24B, even if the degree of expansion of the negative electrode layers 24A and 24B differs, the negative electrode layer 24A and the positive electrode layer 21A, and the negative electrode layer 24B and the positive electrode layer 21B can be individually short-circuited. Conversely, the positive and negative electrode layers that are not overcharged are not short-circuited. Furthermore, in this embodiment, the negative electrode layers 24A and 24B are located outside the positive electrode layers 21A and 21B in the Z direction, which is particularly effective when the negative electrode active material layer 25 is made of a material that expands relatively greatly during overcharge, such as a lithium-based material or a silicon-based material.

[0036] Second Embodiment In the overcharge prevention unit 7 of the first embodiment, the conductors 70 and 72 reversibly come into contact with each other as the laminate 2 expands in the Z direction, and come into a non-contact state when the laminate 2 contracts. Repeated loads are applied to the extensions 70a to 70d due to the reversible contact with the end 72b. This embodiment provides a structure that reduces fatigue of the extensions 70a to 70d.

[0037] An example is shown in Figure 3(A). In the example of Figure 3(A), the portion corresponding to the extended portion 70d in the first embodiment is composed of an inclined portion 70e and a flat portion 70f. The inclined portion 70e is inclined in a direction approaching the end portion 72b from the extended portion 70c side. The flat portion 70f extends from the end portion of the inclined portion 70e (the end portion on the end portion 72b side) and forms a flat surface that functions as an electrical contact portion that comes into contact with the end portion 72b.

[0038] 3(A), when the conductor 72 is displaced and comes into contact with the flat portion 71f due to expansion of the laminate 2, the inclined portion 70e is likely to elastically deform in a direction that changes the inclination angle. When the conductor 72 comes into contact with the conductor 70, the load that the conductor 70 receives is absorbed by the inclined portion 70e, so that stress can be prevented from acting on the entire conductor 70.

[0039] Fig. 3(B) shows another example. In the example of Fig. 3(B), the portion corresponding to the extension portion 70d of the first embodiment is composed of an inclined portion 70g and a flat portion 70h. The inclined portion 70g is inclined in a direction approaching the end portion 72b from the extension portion 70c side. The flat portion 70h extends from the end portion of the inclined portion 70g (the end portion on the end portion 72b side) and functions as an electrical contact portion that comes into contact with the end portion 72b.

[0040] The support member 73 has a portion 73a that follows the sloped portion 70g. In the illustrated example, the portion 73a is an inclined portion that follows the slope of the sloped portion 70g, but it may be an arc-shaped portion (R-shaped portion) that follows the sloped portion 70g.

[0041] In the example of FIG. 3(B), when the expansion of the laminate 2 displaces the conductor 72 and brings it into contact with the flat portion 71h, the inclined portion 70g is more likely to elastically deform in a direction that changes its inclination angle. When the conductor 72 and the conductor 70 come into contact, the load applied to the conductor 70 is absorbed by the inclined portion 70g, preventing stress from acting on the entire conductor 70. Elastic deformation of the inclined portion 70g may cause the inclined portion 70g and the portion 73a of the support member 73 to come into contact with each other. However, because the portion 73a is formed along the inclined portion 70g, it is possible to prevent large stresses from acting between the inclined portion 70g and the support member 73 when the inclined portion 70g and the portion 73a of the support member 73 come into contact with each other. This prevents wear and plastic deformation not only of the inclined portion 70g but also of the support member 73.

[0042] Third Embodiment The overcharge prevention unit 7 of the first embodiment brings the conductor 70 and the conductor 72 into contact by utilizing the expansion of the laminate 2 as a state change of the laminate 2, but it may also utilize heat generated by the laminate 2. Figure 4(A) is a cross-sectional view showing the structure of the overcharge prevention unit 7A of this embodiment, and corresponds to the cross-sectional view taken along line BB in Figure 1(A).

[0043] The overcharge prevention unit 7A has conductors 70 and 72, and the structure of the conductor 72 is the same as that of the conductor 72 in the first embodiment. The conductor 70 is composed only of the extension portion 70a in the first embodiment, and does not have the extension portions 70b to 70d. In this embodiment, the extension portion 70a functions as an electrical contact portion that comes into contact with the end portion 72b.

[0044] A thermal melting material 74 is interposed between each extension portion 70a and each end portion 72b. The thermal melting material 74 is an insulating resin material such as PE, PVC, PS, PP, or PC. The laminate 2 generates heat upon overcharge, but the melting point of the thermal melting material 74 is lower than the heat generation temperature at which the laminate 2 is damaged, and is lower than the melting point of the organic polymer compound binder that binds together the particles of the material that make up the positive electrode active material layer 22, the negative electrode active material layer 25, and the solid electrolyte layer 27. The melting point of the thermal melting material 74 is also lower than the melting points of the resin layers included in the all-solid-state battery 1, such as the resin layer of the exterior body 8.

[0045] The overcharge prevention unit 7A includes a biasing member 75. The biasing member 75 biases the conductor 70 and the conductor 72 in a direction in which they come into contact at the portion where the thermal melt material 74 is located. The biasing member 75 is made of, for example, a spring material, and in the illustrated example, has a shape that sandwiches the two end portions 72b in the Z direction. The biasing member 75 may be entirely covered with an insulating layer.

[0046] The operation of the overcharge prevention unit 7A having such a configuration will be described with reference to Figures 4(A) and 4(B). When charging and discharging of the laminate 2 is performed properly, the extension portion 70a and the end portion 72b are not in contact with each other because the thermally meltable material 74 is interposed between them as shown in Figure 4(A). This means that the conductors 70 and 72 are not electrically connected. In other words, the positive electrode current collector 23 and the negative electrode current collector 26 are not short-circuited.

[0047] On the other hand, when the laminate 2 is charged and overcharged, the laminate 2 expands and generates heat, and the exterior body 8 follows this deformation. This heat causes the thermal melting material 74 to melt, and the biasing member 75, indicated by the solid arrow in FIG. 4(B), biases the end 72b, bringing it into contact with the extension 70a. The contact between the extension 70a and the end 72b establishes electrical continuity between the conductor 70 and the conductor 72. As a result, the positive electrode current collector 23 and the negative electrode current collector 26 are short-circuited, causing self-discharge (the dashed arrow in FIG. 4(B) illustrates the direction of current flow). As a result, overcharging of the laminate 2 is suppressed.

[0048] Even when charging of the laminate 2 is completed and the temperature of the laminate 2 drops, the contact state between the extension portion 70a and the end portion 72b is maintained, and the all-solid-state battery 1 becomes unusable thereafter. In this embodiment, heat generation in the laminate 2 causes irreversible contact between the conductor 70 and the conductor 72. By using, as the thermal melt material 74, a material having a melting point temperature corresponding to the temperature at which continued use of the laminate 2 becomes difficult, it is possible to prevent continued use of the all-solid-state battery 1 that has deteriorated due to overcharging.

[0049] Although the present embodiment uses the biasing member 75, it is also possible to employ a configuration that does not use the biasing member 75. In this case, the conductor 72 is made of a spring material, and the conductor 72 itself only needs to have elasticity in the direction in which the end 72b contacts the extension portion 70a.

[0050] <Fourth embodiment> Like the third embodiment, this embodiment also utilizes heat generation from the laminate 2, but utilizes a change in electrical resistance due to temperature to establish electrical continuity between the conductors 70 and 72. Figure 5(A) is a cross-sectional view showing the structure of the overcharge prevention unit 7B of this embodiment, and corresponds to the cross-sectional view taken along line BB in Figure 1(A).

[0051] The overcharge prevention unit 7B has conductors 70 and 72, and the structure of the conductor 72 is the same as that of the conductor 72 in the first embodiment. The conductor 70 is composed only of the extension portion 70a in the first embodiment, and does not have the extension portions 70b to 70d.

[0052] An NTC thermistor 76 is interposed between the extension portion 70a and each end portion 72b. The resistance of the NTC thermistor 76 changes with temperature, and in particular, the resistance decreases as the temperature increases. As for the temperature-resistance characteristics, it is desirable for the NTC thermistor 76 to have a significantly large resistance corresponding to the normal temperature of the laminate 2, and a significantly small resistance corresponding to the heat generated by overcharging the laminate 2.

[0053] 5(B) shows an example of the temperature-resistance characteristics of the NTC thermistor 76. A temperature equal to or higher than temperature T is set as the temperature during overcharge. At temperatures equal to or higher than temperature T, the NTC is substantially in a conductive state. The resistance of the NTC thermistor 76 at temperature T is equal to the resistance of the solid electrolyte layer 76, for example.

[0054] The operation of the overcharge prevention unit 7B having such a configuration will be described. When charging and discharging of the laminate 2 is performed appropriately, the NTC thermistor 76 has a predetermined resistance. Because a large resistance exists between the extension portion 70a and the end portion 72b, there is substantially no conduction between the conductor 70 and the conductor 72. In other words, there is no short circuit between the positive electrode current collector 23 and the negative electrode current collector 26.

[0055] On the other hand, when the laminate 2 is charged and overcharged, the laminate 2 expands and generates heat, and the exterior body 8 follows this deformation. This heat generation reduces the resistance of the NTC thermistor 76. As a result, electrical continuity is established between the extension portion 70a and the end portion 72b. The positive electrode current collector 23 and the negative electrode current collector 26 are short-circuited, causing self-discharge (the dashed arrow in FIG. 5(A) illustrates the direction of current flow). As a result, overcharging of the laminate 2 is suppressed.

[0056] When charging of the laminate 2 is completed and the temperature of the laminate 2 drops, the resistance of the NTC thermistor 76 increases, so that the conductors 70 and 72 are not substantially electrically connected, and the positive electrode current collector 23 and the negative electrode current collector 26 return to a state where they are not short-circuited.

[0057] That is, in the overcharge prevention unit 7, the conductors 70 and 72 are reversibly brought into conduction due to heat generation in the laminate 2, and are brought into a non-conductive state when the temperature of the laminate 2 drops. Therefore, even if the laminate 2 temporarily falls into an overcharged state, the laminate 2 can be used continuously.

[0058] Fifth Embodiment In the first embodiment, one overcharge prevention unit 7 is disposed in one location. However, multiple overcharge prevention units 7 may be disposed in multiple locations. FIG. 6(A) is a plan view of an all-solid-state battery 1 showing such an example. In the illustrated example, two overcharge prevention units 7 are disposed inside the exterior housing 8 between the laminate 2 and the side 8a, spaced apart in the Y direction. The two overcharge prevention units 7 are provided independently of the lead tabs 3 and 4 and the current collecting tabs 5 and 6, and are disposed at positions sandwiching the current collecting tab 5 in the Y direction. Providing multiple overcharge prevention units 7 more reliably suppresses overcharge of the laminate 2. Furthermore, by disposing the overcharge prevention units 7 at different locations in the Y direction, even if the laminate 2 expands unevenly due to overcharge, the overcharge prevention units 7 at the corresponding locations short-circuit the conductors 70 and 72, thereby suppressing overcharge of the laminate 2.

[0059] In the example of Fig. 6(A), the overcharge prevention unit 7 is disposed between the laminate 2 and side 8a, but an overcharge prevention unit with a similar function to the overcharge prevention unit 7 may be disposed between the laminate 2 and side 8b. Also, an overcharge prevention unit may be disposed between the laminate 2 and side 8a and between the laminate 2 and side 8b. In the example of Fig. 6(A), multiple overcharge prevention units 7 are disposed at multiple locations, but multiple overcharge prevention units 7A and overcharge prevention units 7B may be disposed at multiple locations.

[0060] Moreover, different types of overcharge prevention units may be arranged in multiple locations. FIG. 6(B) shows one example. In the illustrated example, two types of overcharge prevention units, 7 and 7A, are arranged inside the exterior body 8, between the laminate 2 and the side 8a, spaced apart in the Y direction. Generally, the state of the laminate 2 changes during overcharge, first causing expansion, followed by high-temperature heat generation. When heat generation occurs, the battery's lifespan is often over, but continued use is often possible at the expansion stage.

[0061] In the configuration example of FIG. 6(B), during the expansion stage, which is the first stage of overcharging, the overcharge prevention unit 7 prevents overcharging of the laminate 2. As described above, the overcharge prevention unit 7 is structured to reversibly short-circuit the positive electrode current collector 23 and the negative electrode current collector 26, allowing the all-solid-state battery 1 to continue to be used. On the other hand, during the heat generation stage, which is the second stage of overcharging, the overcharge prevention unit 7A prevents overcharging of the laminate 2. As described above, the overcharge prevention unit 7A is structured to irreversibly short-circuit the positive electrode current collector 23 and the negative electrode current collector 26, allowing the all-solid-state battery 1 to be subsequently rendered unusable.

[0062] Sixth Embodiment The overcharge prevention units 7 and 7A of the first and third embodiments may be combined to form a single overcharge prevention unit. That is, the two overcharge prevention units 7 and 7A in FIG. 6(B) may be configured as a single overcharge prevention unit. FIG. 7(A) is a cross-sectional view showing the structure of an overcharge prevention unit 7C of this embodiment, and corresponds to the cross-sectional view taken along line BB in FIG. 1(A). FIG. 7(B) is a cross-sectional view taken along line CC in FIG. 7(A).

[0063] Overcharge prevention unit 7C has a structure in which extension portions 70b to 70d of overcharge prevention unit 7 and biasing member 75 of overcharge prevention unit 7A are arranged in the Y direction, and has heat-melting material 77 that integrates support member 73 of overcharge prevention unit 7 and heat-melting material 74 of overcharge prevention unit 7A. Heat-melting material 77 has portion 77a that functions as support member 73 of overcharge prevention unit 7 and portion 77b that functions as heat-melting material 74 of overcharge prevention unit 7A, and is made of the same material as heat-melting material 74.

[0064] In the expansion stage, which is the first stage of overcharging, the overcharge prevention unit 7C having such a configuration causes the extension portion 70d and the end portion 72b to come into contact with each other due to displacement of the conductor 72 caused by expansion, thereby reversibly short-circuiting the positive electrode current collector 23 and the negative electrode current collector 26, thereby preventing overcharging of the laminate 2. On the other hand, in the heat generation stage, which is the second stage of overcharging, melting of the thermally meltable material 77 causes the extension portion 70a and the end portion 72b to come into contact with each other, thereby irreversibly short-circuiting the positive electrode current collector 23 and the negative electrode current collector 26, thereby preventing overcharging of the laminate 2. The all-solid-state battery 1 can then be rendered unusable.

[0065] <Summary of the embodiment> The above-described embodiments disclose at least the following all-solid-state batteries.

[0066] 1. The all-solid-state battery of the above embodiment is a laminate (2) in which positive electrode layers (21A, 21B), a solid electrolyte layer (27), and negative electrode layers (24A, 24B) are laminated; an exterior body (8) that surrounds and seals the laminate (2) and can follow deformation of the laminate (2) in the stacking direction (Z); An all-solid-state battery (1) comprising: an overcharge prevention unit (7-7C) that is enclosed and sealed together with the laminate (2) in the exterior body (8) and that can short-circuit a positive electrode current collector (23) of the positive electrode layer (21A, 21B) and a negative electrode current collector (26) of the negative electrode layer (24A, 24B); The overcharge prevention unit (7-7C) a first conductor (70) extending from one of the positive electrode current collector (23) and the negative electrode current collector (26); a second conductor (72) extending from the other of the positive electrode current collector (23) and the negative electrode current collector (26) and spaced apart from the first conductor (70); The first conductor (70) and the second conductor (72) are brought into conduction by the change in state of the laminate (2). According to this embodiment, an all-solid-state battery capable of suppressing overcharging can be provided without providing a special structure on the exterior of the exterior body. Unlike liquid-based secondary batteries, the interior of the exterior body of the all-solid-state battery does not contain liquid. Therefore, a conductor can be used inside the exterior body to more reliably short-circuit and release the short circuit between the positive electrode current collector and the negative electrode current collector.

[0067] 2. In the above embodiment, As a result of the state change, the laminate (2) expands in the stacking direction (Z), causing the first conductor (70) and the second conductor (72) to come into contact with each other, thereby establishing electrical continuity therebetween. According to this embodiment, the positive electrode current collector and the negative electrode current collector can be short-circuited by utilizing the displacement of the conductor due to the expansion of the laminate.

[0068] 3. In the above embodiment, the overcharge prevention unit (7A) has a heat-melting material (74) interposed between the first conductor (70) and the second conductor (72), As a result of the change in state, the heat generated by the laminate (2) melts the thermally meltable material (74), bringing the first conductor (70) and the second conductor (72) into contact with each other and establishing electrical continuity therebetween. According to this embodiment, the positive electrode current collector and the negative electrode current collector can be short-circuited by utilizing the melting of the thermally meltable material due to the heat generated by the laminate.

[0069] 4. In the above embodiment (FIGS. 6(B) and 7(A)), the overcharge prevention unit (7, 7A, 7C) has a heat-melting material (74, 77) interposed between the first conductor (70) and the second conductor, As a result of the state change, the laminate (2) expands in the stacking direction (Z), causing the first conductor (70) and the second conductor (72) to reversibly come into contact with each other and become conductive therebetween; As a result of the state change, the heat generated by the laminate (2) melts the thermally meltable materials (74, 77), causing the first conductor (70) and the second conductor (72) to come into irreversible contact with each other, thereby establishing electrical continuity. According to this embodiment, if the overcharge stage is the expansion stage, the conductors are short-circuited to allow continued use, and if the overcharge stage is the heat generation stage, the conductors are short-circuited to prevent continued use.

[0070] 5. In the above embodiment, the overcharge prevention unit (7B) has an NTC thermistor (76) interposed between the first conductor (70) and the second conductor (72); As a result of the state change, the resistance value of the NTC thermistor (76) decreases due to heat generation from the laminate (2), and the first conductor (70) and the second conductor (72) become conductive. According to this embodiment, the positive electrode current collector and the negative electrode current collector can be short-circuited by utilizing a change in resistance of the NTC thermistor due to heat generation by the laminate.

[0071] 6. In the above embodiment, The first conductor (70) has first electrical contact portions (70d, 70f, 70h), the second conductor (72) has a second electrical contact portion (72b) that comes into contact with the first electrical contact portions (70d, 70f, 70h) due to the expansion; The first electrical contact portion (70f) and the second electrical contact portion (72b) have flat surfaces. According to this embodiment, when the laminate expands, the electrical contact portions can be brought into more reliable contact with each other, thereby establishing electrical continuity between the conductors.

[0072] 7. In the above embodiment, The first conductor (70) has first electrical contact portions (70d, 70f, 70h), the second conductor (72) has a second electrical contact portion (72b) that comes into contact with the first electrical contact portions (70d, 70f, 70h) due to the expansion; The first conductor (70) has inclined portions (70e, 70g) inclined in a direction approaching the second electrical contact portion (72b), The first electrical contact portions (70f, 70h) are provided at the ends of the inclined portions (70e, 70g) on ​​the side of the second electrical contact portion (72b). According to this embodiment, the electrical contact portions can be repeatedly brought into contact with and separated from each other by the elastic deformation of the inclined portion.

[0073] 8. In the above embodiment, The first conductor (70) a first extending portion (70a) extending in a direction away from the laminate (2); a second extension portion (70b) bent from the first extension portion (70a) and extending in one direction of the stacking direction (Z); a third extension portion (70c) bent from the second extension portion (70b) and extending in a direction approaching the stack (2); and fourth extension portions (70e, 70f, 70g, 70h) bent from the third extension portion (70c) and extending in the other direction of the stacking direction (Z), The second conductor (72) has an end (72b) that is inserted between the first extension portion (70a) and the third extension portion (70c). According to this embodiment, stable operation is possible by limiting the contact areas when the laminated body expands.

[0074] 9. In the above embodiment, The overcharge prevention unit (7) a support member (73) that is provided to fill the gap between the first extension portion (70a) and the third extension portion (70c) and supports the end portion (72b); the fourth extension portions (70g, 70h) are inclined in a direction approaching the stack (2) from the third extension portion (70c) in the other direction, The support member (73) has a portion (73a) that follows the slope of the fourth extension portion (70g, 70h). According to this embodiment, it is possible to prevent a large stress from acting between the inclined portion 70 and the support member when the inclined portion and the portion of the support member come into contact with each other again after they have separated from each other.

[0075] 10. In the above embodiment, The overcharge prevention units (7A, 7C) include biasing members (75) that bias the first conductor (70) and the second conductor (72) in a direction in which they come into contact with each other at the locations where the thermally fusible materials (73, 77) are arranged. According to this embodiment, when the thermal melting material melts, the conductors can be brought into contact with each other more reliably.

[0076] 11. In the all-solid-state battery of the above embodiment, a first lead tab (3); a second lead tab (4), The laminate (2) is disposed between the first lead tab (3) and the second lead tab (4), The exterior body (8) has a rectangular shape having four sides (8a-8d) when viewed in the stacking direction (Z), The overcharge prevention section (7-7C) is located between the laminate (2) and the side (8a, 8b) of the four sides (8a-8d) on which the first lead tab (3) or the second lead tab (4) is provided. According to this embodiment, the overcharge prevention unit can be disposed by utilizing the empty space inside the exterior body.

[0077] 12. In the above embodiment, The hot melt materials (73, 77) have a melting point lower than that of the binder contained in the positive electrode layers (21A, 21B), the negative electrode layers (24A, 24B), or the solid electrolyte layer (27). According to this embodiment, overcharging can be suppressed before the laminate is damaged.

[0078] 13. In the above embodiment, The negative electrode layers (24A, 24B) contain a lithium-based material, a silicon-based material, or a tin-based material as a negative electrode active material. According to this embodiment, overcharging can be prevented in an all-solid-state battery that uses, as the negative electrode active material, a lithium-based material, a silicon-based material, or a tin-based material that expands relatively greatly during overcharging.

[0079] 14. In the above embodiment, The positive electrode layers (21A, 21B) are Two positive electrode active material layers (22) in the stacking direction (Z), a common positive electrode current collector (23) between the two positive electrode active material layers (22), The negative electrode layers (24A, 24B) are a first negative electrode layer (24A) on the outer side of the positive electrode layer (21A, 21B) in one direction of the stacking direction; a second negative electrode layer (24B) on the outer side of the positive electrode layer (21A, 21B) in the other direction of the stacking direction; Including, The negative electrode current collector (26) is a first negative electrode current collector (26) included in the first negative electrode layer (24A) and positioned as the outermost layer in one direction in the stacking direction of the stack; a second negative electrode current collector (26) that is included in the second negative electrode layer (24B) and is located in the outermost layer in the other direction in the stacking direction of the stack, the first conductor (70) extends from the positive electrode current collector (23), The second conductor (72) includes a conductor (72) extending from the first negative electrode current collector (26) and a conductor (72) extending from the second negative electrode current collector (26). According to this embodiment, overcharging can be prevented for each layer.

[0080] 15. In the above embodiment The first conductor (70) has first electrical contact portions (70d, 70f, 70h), the second conductor (72) has a second electrical contact portion that comes into contact with the first electrical contact portion due to the expansion; The first conductor includes a portion that is covered with an insulating layer (71). According to this embodiment, it is possible to prevent unintentional contact between the first conductor and the second conductor.

[0081] 16. The all-solid-state battery of the above embodiment is The lead tabs (3, 4) and the current collecting tabs (5, 6) are provided. The overcharge prevention portion (7, 7A, 7B) is provided independently of the lead tab and the current collecting tab. According to this embodiment, the overcharge prevention section can prevent physical effects such as damage to the lead tabs and the current collecting tabs.

[0082] Although the embodiments of the invention have been described above, the invention is not limited to the above-described embodiments, and various modifications and variations are possible within the scope of the gist of the invention. [Explanation of symbols]

[0083] 1 all-solid-state battery, 2 laminated body, 7 overcharge prevention unit, 8 exterior body

Claims

1. a laminate formed by stacking a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; an exterior body that surrounds and seals the laminate and is capable of following deformation of the laminate in the stacking direction; An all-solid-state battery comprising: an overcharge prevention unit that is enclosed and sealed together with the laminate in the exterior body and that can short-circuit a positive electrode current collector of the positive electrode layer and a negative electrode current collector of the negative electrode layer; The overcharge prevention unit is a first conductor extending from one of the positive electrode current collector and the negative electrode current collector; a second conductor extending from the other of the positive electrode current collector and the negative electrode current collector and spaced apart from the first conductor, the first conductor includes a portion laminated on the laminate; The expansion of the laminate in the stacking direction brings the first conductor and the second conductor into contact with each other, thereby establishing electrical conduction therebetween. An all-solid-state battery characterized by:

2. a laminate formed by stacking a positive electrode layer, a solid electrolyte layer, and a negative electrode layer; an exterior body that surrounds and seals the laminate and is capable of following deformation of the laminate in the stacking direction; An all-solid-state battery comprising: an overcharge prevention unit that is enclosed and sealed together with the laminate in the exterior body and that can short-circuit a positive electrode current collector of the positive electrode layer and a negative electrode current collector of the negative electrode layer; The overcharge prevention unit is a first conductor extending from one of the positive electrode current collector and the negative electrode current collector; a second conductor extending from the other of the positive electrode current collector and the negative electrode current collector and spaced apart from the first conductor, the first conductor includes a first portion laminated on the laminate; the second conductor includes a second portion laminated on the laminate; the first portion is located outward of the second portion in the stacking direction of the stack, The expansion of the laminate in the stacking direction brings the first conductor and the second conductor into contact with each other, thereby establishing electrical conduction therebetween. An all-solid-state battery characterized by:

3. The all-solid-state battery according to claim 1 or 2, the overcharge prevention unit has a heat-melting material interposed between the first conductor and the second conductor, expansion of the laminate in the lamination direction causes the first conductor and the second conductor to reversibly contact each other and become conductive therebetween; The heat generated by the laminate melts the thermal melting material, causing the first conductor and the second conductor to come into irreversible contact with each other, thereby establishing electrical continuity therebetween. An all-solid-state battery characterized by:

4. The all-solid-state battery according to claim 1 or 2, the first conductor has a first electrical contact portion; the second conductor has a second electrical contact portion that comes into contact with the first electrical contact portion due to the expansion; the first electrical contact portion and the second electrical contact portion have flat surfaces; An all-solid-state battery characterized by:

5. The all-solid-state battery according to claim 1 or 2, the first conductor has a first electrical contact portion; the second conductor has a second electrical contact portion that comes into contact with the first electrical contact portion due to the expansion; the first conductor has an inclined portion inclined in a direction approaching the second electrical contact portion, the first electrical contact portion is provided at an end of the inclined portion on the side of the second electrical contact portion; An all-solid-state battery characterized by:

6. The all-solid-state battery according to claim 1 or 2, The first conductor is a first extension portion extending in a direction away from the stack; a second extension portion bent from the first extension portion and extending in one direction of the stacking direction; a third extension portion bent from the second extension portion and extending in a direction approaching the stack; a fourth extension portion bent from the third extension portion and extending in another direction of the stacking direction, the second conductor has an end portion inserted between the first extension portion and the third extension portion; An all-solid-state battery characterized by:

7. The all-solid-state battery according to claim 6, The overcharge prevention unit is a support member that is provided to fill a gap between the first extension portion and the third extension portion and supports the end portion, the fourth extension portion is inclined in a direction approaching the stacked body in the other direction from the third extension portion, the support member has a portion that follows the slope of the fourth extension portion, An all-solid-state battery characterized by:

8. The all-solid-state battery according to claim 3, the overcharge prevention unit includes a biasing member that biases the first conductor and the second conductor in a direction in which they come into contact with each other at a location where the thermal melting material is disposed; An all-solid-state battery characterized by:

9. The all-solid-state battery according to claim 1 or 2, a first lead tab; a second lead tab; the laminate is disposed between the first lead tab and the second lead tab; The exterior body has a rectangular shape having four sides when viewed in the stacking direction, the overcharge prevention unit is located between the laminate and one of the four sides on which the first lead tab or the second lead tab is provided. An all-solid-state battery characterized by:

10. The all-solid-state battery according to claim 3, the hot-melt material has a melting point lower than that of a binder contained in the positive electrode layer, the negative electrode layer, or the solid electrolyte layer; An all-solid-state battery characterized by:

11. The all-solid-state battery according to claim 1 or 2, The negative electrode layer contains a lithium-based material, a silicon-based material, or a tin-based material as a negative electrode active material. An all-solid-state battery characterized by:

12. The all-solid-state battery according to claim 1 or 2, The positive electrode layer is two positive electrode active material layers in the stacking direction; a common positive electrode current collector between the two positive electrode active material layers, The negative electrode layer is a first negative electrode layer located outside the positive electrode layer in one direction of the stacking direction; a second negative electrode layer on the outer side of the positive electrode layer in the other direction of the stacking direction; Including, The negative electrode current collector is a first negative electrode current collector included in the first negative electrode layer and positioned as an outermost layer in the one direction in the stacking direction of the laminate; a second negative electrode current collector included in the second negative electrode layer and positioned as an outermost layer in the other direction in the stacking direction of the laminate, the first conductor extends from the positive electrode current collector, the second conductor includes a conductor extending from the first negative electrode current collector and a conductor extending from the second negative electrode current collector; An all-solid-state battery characterized by:

13. The all-solid-state battery according to claim 1 or 2, the first conductor has a first electrical contact portion; the second conductor has a second electrical contact portion that comes into contact with the first electrical contact portion due to the expansion; the first conductor includes a portion covered with an insulating layer; An all-solid-state battery characterized by:

14. The all-solid-state battery according to claim 1 or 2, A lead tab and a current collecting tab are provided, the overcharge prevention portion is provided independently of the lead tab and the current collecting tab; An all-solid-state battery characterized by:

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