All-solid battery and battery module

Abstract

To provide an all-solid battery with small pressure variations.SOLUTION: An all-solid battery includes a plurality of electrode stacks, each 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, and elastic sheets disposed between the electrode stacks, and some of the plurality of electrode stacks directly contact adjacent electrode stacks, and the Young's modulus of the elastic sheets is 30 MPa or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In recent years, research and development into secondary batteries that contribute to energy efficiency has been conducted to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. Among secondary batteries, all-solid-state batteries, which are composed of multiple electrode stacks each consisting of a positive electrode, a solid electrolyte, and a negative electrode, are considered promising.

[0003] In all-solid-state batteries, in order to prevent performance degradation and defects such as short circuits caused by deposition of metals and the like on the electrodes, a configuration is widely adopted in which multiple secondary batteries are stacked in the thickness direction of the electrodes and the stack of all-solid-state batteries is pressurized (constrained) in the thickness direction to suppress local deposition and the like (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-67647 Summary of the Invention [Problem to be solved by the invention]

[0005] In technology related to all-solid-state batteries, it is desirable to apply uniform pressure to the all-solid-state battery. Patent Document 2 describes a technology in which elastic pads compressible in the thickness direction are placed between electrode laminates to absorb thickness variations of the electrodes. However, in all-solid-state batteries in which many thin electrode laminates are stacked, the increase in the overall thickness of the battery due to the components that absorb the thickness variations of the electrodes cannot be ignored. Therefore, it is desirable to suppress the increase in the thickness of the all-solid-state battery while minimizing the variation in pressure acting on the all-solid-state battery.

[0006] The present invention has been made in view of the above-described circumstances, and aims to provide an all-solid-state battery and a battery module that suppress an increase in thickness and reduce variations in pressure acting on an electrode stack, thereby contributing to energy efficiency. [Means for solving the problem]

[0007] (1) The present invention provides an all-solid-state battery comprising: a plurality of electrode laminates each 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; and an elastic sheet disposed between the electrode laminates, wherein some of the plurality of electrode laminates directly contact adjacent electrode laminates; and the Young's modulus of the elastic sheet is 30 MPa or less.

[0008] In the all-solid-state battery (1), by using a small number of elastic sheets with a relatively small Young's modulus, it is possible to suppress an increase in thickness while suppressing variations in pressure acting on all electrode laminates.

[0009] (2) The all-solid-state battery according to (1), wherein the number of the elastic sheets is two or more and less than half the number of the electrode stacks.

[0010] According to the all-solid-state battery of (2), the thickness of the entire all-solid-state battery can be significantly reduced while sufficiently suppressing variations in the pressure acting on the electrode laminate.

[0011] (3) The all-solid-state battery according to (1) or (2), wherein the Young's modulus of the elastic sheet is 15 MPa or more and 20 MPa or less.

[0012] According to the all-solid-state battery of (3), the variation in pressure acting on the electrode laminate can be more reliably suppressed.

[0013] (4) A battery module comprising: a plurality of stacked all-solid-state batteries according to any one of claims (1) to (3); and a pressure mechanism that applies a confining pressure to constrain the all-solid-state batteries in a thickness direction, wherein the confining pressure applied by the pressure mechanism is 3.0 MPa or less.

[0014] According to the battery module of (4), the pressure acting on the electrode laminate can be optimized, so that a decrease in performance of the all-solid-state battery due to local deposition of metals or the like can be prevented.

[0015] (5) The battery module according to (4), wherein the restraining pressure applied by the pressurizing mechanism is 0.5 MPa or more and 2.0 MPa or less.

[0016] (5) The battery module can more reliably prevent the performance of the all-solid-state battery from deteriorating. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an all-solid-state battery and a battery module in which an increase in thickness is suppressed and the variation in pressure acting on an electrode stack is small. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view of an all-solid-state battery according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the configuration of the all-solid-state battery of FIG. [Figure 3] 2 is a schematic plan view showing the configuration of a battery module including the all-solid-state battery of FIG. 1. [Figure 4] 10 is a graph showing the variation in pressure when an elastic sheet having a Young's modulus of 18.5 MPa is used and the restraining pressure is set to 1.0 MPa. [Figure 5] 10 is a graph showing the variation in pressure when an elastic sheet having a Young's modulus of 18.5 MPa is used and the restraining pressure is set to 3.0 MPa. [Figure 6] 10 is a graph showing the variation in pressure when an elastic sheet having a Young's modulus of 29.4 MPa is used and the restraining pressure is set to 1.0 MPa. [Figure 7] 10 is a graph showing the variation in pressure when an elastic sheet having a Young's modulus of 29.4 MPa is used and the restraining pressure is set to 3.0 MPa. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are merely examples of the present invention, and the present invention is not limited to the following.

[0020] [All-solid battery] Fig. 1 is a perspective view of an all-solid-state battery (all-solid-state battery cell) 1 according to one embodiment of the present invention. Fig. 2 is a schematic cross-sectional view showing the configuration of the all-solid-state battery 1. Note that in Fig. 1, each component is exaggerated for clarity, and in Fig. 2 in particular, the thickness of each component is exaggerated, but the actual thickness of each component is sufficiently small compared to its planar dimensions.

[0021] The all-solid-state battery 1 includes a plurality of electrode laminates 10, an elastic sheet 20 disposed between the electrode laminates 10, an outer casing 30 that houses the electrode laminates 10 and the elastic sheet 20, and a positive electrode tab 41 and a negative electrode tab 42 that extend from the plurality of electrode laminates 10 to the outside of the outer casing 30.

[0022] The number of electrode laminates 10 in the all-solid-state battery 1 is, for example, preferably 3 to 10, more preferably 4 to 7. Increasing the number of electrode laminates 10 can increase the output current, but if the number of electrode laminates 10 is too large, the thickness of the all-solid-state battery 1 will be excessively large. Furthermore, in the all-solid-state battery 1, at least some of the electrode laminates 10 directly abut against adjacent electrode laminates 10 without an elastic sheet 20 therebetween. In the illustrated embodiment, the number of electrode laminates 10 is five, and an elastic sheet 20 is interposed between the first and second electrode laminates 10 from the top, and between the third and fourth electrode laminates 10 from the top, while the second and third electrode laminates 10, and the fourth and fifth electrode laminates 10 from the top directly abut against each other.

[0023] The electrode stack 10 includes one positive electrode layer 11, two negative electrode layers 12 arranged opposite each other with the positive electrode layer 11 interposed therebetween, and two solid electrolyte layers 13 arranged between the positive electrode layer 11 and the negative electrode layer 12, respectively.

[0024] The positive electrode layer 11 has a positive electrode current collector 111 and two positive electrode active material layers 112 laminated on both surfaces of the positive electrode current collector 111. The positive electrode current collector 111 is connected to a positive electrode tab 41.

[0025] The positive electrode current collector 111 is not particularly limited in material or shape as long as it has the function of collecting current from the positive electrode layer 11. Examples of materials for the positive electrode current collector 111 include aluminum, aluminum alloys, stainless steel, nickel, iron, and titanium, and among these, aluminum, aluminum alloys, and stainless steel are preferred. Examples of the shape of the positive electrode current collector 111 include foil, plate, mesh, nonwoven fabric, and foam.

[0026] The positive electrode active material layer 112 contains at least one type of positive electrode active material. There are no particular limitations on the positive electrode active material, and any material that is used in the positive electrode layer of a general all-solid-state battery can be used. As the positive electrode active material, for example, a layered active material containing lithium, a spinel-type active material, an olivine-type active material, etc. can be used. Specific examples of the positive electrode active material include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), LiNi p Mn q Co r O2(p+q+r=1), LiNi p Al q Co r O2 (p+q+r=1), lithium manganese oxide (LiMn2O4), Li 1+x Mn 2-x-y Examples include heteroelement-substituted Li-Mn spinel represented by MO4 (x+y=2, M=at least one selected from Al, Mg, Co, Fe, Ni, and Zn), lithium titanate (oxide containing Li and Ti), and lithium metal phosphate (LiMPO4, M=at least one selected from Fe, Mn, Co, and Ni).

[0027] The positive electrode active material layer 112 may optionally contain a solid electrolyte from the viewpoint of improving lithium ion conductivity. It may also optionally contain a conductive additive to improve conductivity. Furthermore, it may also optionally contain a binder from the viewpoint of exhibiting flexibility, etc. There are no particular limitations on the solid electrolyte, conductive additive, and binder, and those used in the positive electrode layer of a general all-solid-state battery may be used.

[0028] Each negative electrode layer 12 has a negative electrode current collector 121 and a negative electrode active material layer 122 laminated on the surface of the negative electrode current collector 121 facing the solid electrolyte layer 13. The negative electrode current collector 121 is connected to a negative electrode tab 42.

[0029] The material and shape of the negative electrode current collector 121 are not particularly limited as long as it has the function of collecting current from the negative electrode layer 12. Examples of materials for the negative electrode current collector 121 include nickel, copper, and stainless steel. Examples of shapes of the negative electrode current collector 121 include foil, plate, mesh, nonwoven fabric, and foam.

[0030] The negative electrode active material layer 122 is not particularly limited, and can be made of a material that can be used as a negative electrode active material for a solid-state battery. The negative electrode active material layer 122 preferably contains lithium metal as the negative electrode active material. In addition to simple lithium metal, the lithium metal can be, for example, an alloy of lithium with Mg, Si, Au, Ag, In, Ge, Sn, Pb, Al, Zn, or the like. The negative electrode active material layer 122 may be made by forming a layer of a metal that can be alloyed with lithium, and then alloying at least the surface with lithium. In addition to the above, the negative electrode active material layer 122 can also be made of silicon-based active materials such as Si and Si alloys, lithium titanate (Li4Ti5O 12 The electrode may be composed of lithium transition metal oxides such as TiO2, Nb2O3 and WO3, metal sulfides, metal nitrides, carbon materials such as graphite, soft carbon and hard carbon, metallic indium, etc.

[0031] In addition to the above, the negative electrode active material layer 122 may contain, for example, a solid electrolyte, a conductive additive, a binder, etc. Examples of the solid electrolyte include the same solid electrolyte contained in the solid electrolyte layer 13 described below. Examples of the conductive additive include carbon black, natural graphite, carbon fiber, and carbon nanotubes. Examples of the binder include a nitrile polymer, a polyester polymer, an acrylic acid polymer, a cellulose polymer, a styrene polymer, a styrene-butadiene polymer, a vinyl acetate polymer, a urethane polymer, and a fluoroethylene polymer.

[0032] The solid electrolyte layer 13 is disposed between the positive electrode active material layer 112 and the negative electrode current collector 121. The solid electrolyte layer 13 may have a configuration including a first solid electrolyte layer 131 laminated on the positive electrode active material layer 112 and a second solid electrolyte layer 132 laminated on the negative electrode active material layer 122. The first solid electrolyte layer 131 may be pressure-bonded to the positive electrode layer 11, and the second solid electrolyte layer 132 may be pressure-bonded to the negative electrode layer 12. The outer circumferential edge of the first solid electrolyte layer 131 is preferably larger in size than the outer circumferential edge of the positive electrode layer 11 in a plan view.

[0033] The first solid electrolyte layer 131 may be a substrate-containing body including a porous substrate and a first solid electrolyte composition filled in the pores of the porous substrate. The second solid electrolyte layer 132 may be a substrate-free body including a second solid electrolyte composition containing a solid electrolyte and not including a substrate. The porous substrate included in the first solid electrolyte layer 131 may be, for example, a nonwoven fabric or a woven fabric. By pressing the first solid electrolyte layer 131 and the second solid electrolyte layer 132 together and pressing the second solid electrolyte layer 132 against pinholes formed in the first solid electrolyte layer 131, the pinholes can be filled with the second solid electrolyte composition.

[0034] The thickness of the first solid electrolyte layer 131 of the solid electrolyte layer 13 may be the same as or different from the thickness of the second solid electrolyte layer 132. The thickness of the second solid electrolyte layer 132 may be thicker than the thickness of the first solid electrolyte layer 131, for example.

[0035] The first solid electrolyte composition of the first solid electrolyte layer 131 and the second solid electrolyte composition of the second solid electrolyte layer 132 may contain a solid electrolyte and a binder. The solid electrolytes of the first solid electrolyte composition and the second solid electrolyte composition may be the same or different. The first solid electrolyte composition may contain two or more solid electrolytes with different average particle sizes. For example, the first solid electrolyte composition may contain a fine solid electrolyte having an average particle size of 0.1 μm or more and less than 0.5 μm and a coarse solid electrolyte having an average particle size of 1.0 μm or more and 10.0 μm or less. The ratio of the fine solid electrolyte to the coarse solid electrolyte may be in the range of 1:9 to 9:1 by mass. The fine solid electrolyte has the effect of improving the bonding between the first solid electrolyte layer 131 and the positive electrode layer 11. The coarse solid electrolyte has the effect of improving the filling of the solid electrolyte composition in the first solid electrolyte layer 131. The average particle size of the solid electrolyte of the second solid electrolyte composition may be, for example, in the range of 1.0 μm or more and 10.0 μm or less. The average particle size of the solid electrolyte in the first solid electrolyte composition may be smaller than the average particle size of the solid electrolyte in the second solid electrolyte composition, where the average particle size is a value measured by a laser diffraction scattering method.

[0036] The solid electrolytes of the first solid electrolyte composition and the second solid electrolyte composition are not particularly limited as long as they have lithium ion conductivity, and examples thereof include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes.

[0037] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, etc. The sulfide solid electrolyte may have an argyrodite-type crystal structure.

[0038] Examples of oxide solid electrolytes include NASICON-type oxides, garnet-type oxides, and perovskite-type oxides. Examples of NASICON-type oxides include oxides containing Li, Al, Ti, P, and O (e.g., Li 1.5 Al 0.5 Ti 1.5Examples of garnet-type oxides include oxides containing Li, La, Zr, and O (e.g., LiLaZrO 12 Examples of perovskite oxides include oxides containing Li, La, Ti, and O (for example, LiLaTiO3).

[0039] The binders of the first solid electrolyte composition and the second solid electrolyte composition may be the same or different. There are no particular limitations on the type of binder, and binders used in solid electrolyte layers of general all-solid-state batteries can be used. The binder content of the first solid electrolyte composition can be set, for example, in consideration of the adhesion between the first solid electrolyte composition and the porous substrate, and the overall strength and ionic conductivity of the first solid electrolyte layer 131. The binder content of the second solid electrolyte composition can be set, for example, in consideration of the adhesion to the first solid electrolyte layer 131 and the overall ionic conductivity of the second solid electrolyte layer 132. The binder content of the first solid electrolyte composition may be higher than the binder content of the second solid electrolyte composition. The binder content of the first solid electrolyte composition may be, for example, in the range of 1.5 to 10 times the binder content of the second solid electrolyte composition.

[0040] When the all-solid-state battery 1 is pressed in the thickness direction, the elastic sheet 20 distributes the force acting on the electrode laminate 10 in the planar direction, thereby preventing the pressure acting on the electrode laminate 10 from becoming locally excessive. The elastic sheet 20 is disposed only between some of all combinations of two adjacent electrode laminates 10. In other words, where N is the number of electrode laminates 10, the number of elastic sheets 20 is 1 or more and (N-2) or less, and preferably 2 or more and less than half (N / 2) the number of electrode laminates 10. In this way, by reducing the number of elastic sheets 20, an increase in the thickness of the all-solid-state battery 1 can be suppressed.

[0041] The Young's modulus of the elastic sheet 20 is 30 MPa or less, preferably 1 MPa to 30 MPa, and more preferably 15 MPa to 20 MPa. By setting the Young's modulus of the elastic sheet 20 within a certain range, the force restraining the all-solid-state battery 1 in the thickness direction can be appropriately distributed, and the pressure acting on the electrode stack 10 can be appropriately equalized. The Young's modulus of the elastic sheet 20 is measured according to JIS-K7127 (1999).

[0042] The thickness of the elastic sheet 20 is preferably 15 μm or more and 200 μm or less, and more preferably 20 μm or more and 100 μm or less. By setting the thickness of the elastic sheet 20 within a certain range, pressure can be appropriately distributed and the thickness of the electrode stack 10 can be prevented from increasing unnecessarily.

[0043] The elastic sheet 20 can be made of a resin such as polyethylene or polypropylene. As a specific example, the elastic sheet 20 has a specific gravity of 0.91 to 0.92 g / cm. 3 A film made of soft polyethylene, which has a Young's modulus of 100%, can be used. The elastic sheet 20 may also be formed from a porous material with minute pores to obtain an appropriate Young's modulus. Specifically, the elastic sheet 20 may be a porous resin sheet used as a separator in a secondary battery.

[0044] The exterior body 30 can be made of a material such as a laminate film. The laminate film can be a three-layer film having an inner resin layer, a metal layer, and an outer resin layer stacked in this order from the inside. The outer resin layer can be, for example, a polyamide (nylon) layer or a polyethylene terephthalate (PET) layer, the metal layer can be, for example, an aluminum layer, and the inner resin layer can be, for example, a polyethylene layer or a polypropylene layer.

[0045] The material of the positive electrode tab 41 may be the same as or different from the material of the positive electrode current collector 111. The positive electrode tab 41 may be formed integrally with the positive electrode current collector 111. In this embodiment, the positive electrode tab 41 is formed by extending the positive electrode current collector 111 of each electrode stack 10 into a strip shape and stacking these extended portions.

[0046] The material of the negative electrode tab 42 may be the same as or different from the material of the negative electrode current collector 121. The negative electrode tab 42 is formed by extending the negative electrode current collector 121 of each electrode laminate 10 into a strip shape and stacking these extended portions.

[0047] [Battery module] 3 is a schematic plan view showing the configuration of a battery module M according to one embodiment of the present invention, which includes the above-described all-solid-state battery 1. The battery module M includes a plurality of all-solid-state batteries 1 stacked in the thickness direction, and a pressurizing mechanism P that pressurizes the plurality of all-solid-state batteries 1 in the thickness direction.

[0048] The pressure mechanism P applies pressure to restrain the all-solid-state battery 1 in the thickness direction so as to limit expansion of the all-solid-state battery 1 and suppress performance degradation due to expansion of the all-solid-state battery 1. The pressure mechanism P may be any mechanism that can appropriately pressurize the all-solid-state battery 1, and may be configured to pressurize the all-solid-state battery 1 using, for example, an elastic body such as a spring or foam rubber, or may be configured to pressurize the all-solid-state battery 1 using, for example, a screw or the like.

[0049] The confining pressure applied by the pressurizing mechanism P is set to 3.0 MPa or less, preferably 0.1 MPa or more and 3.0 MPa or less, and more preferably 0.5 MPa or more and 2.0 MPa or less. By setting the confining pressure applied by the pressurizing mechanism P within this range, it is possible to appropriately suppress performance degradation due to expansion of the all-solid-state battery 1. The confining pressure is a value obtained by dividing the force applied to the all-solid-state battery by the area of ​​the negative electrode.

[0050] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. [Example]

[0051] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the contents of the following examples.

[0052] As in the above-described embodiment, five electrode stacks were stacked, each consisting of one positive electrode layer sandwiched between two solid electrolyte layers and two negative electrode layers, and an elastic sheet was sandwiched between the first and second electrode stacks, and between the third and fourth electrode stacks, to fabricate an all-solid-state battery. The elastic sheets had a thickness of 70 μm, a Young's modulus of 18.5 MPa, and a specific gravity of 0.91 to 0.92 g / cm. 3 The prototypes were made using a soft polyethylene sheet of this material and a lithium-ion battery separator with a thickness of 20 μm and a Young's modulus of 29.4 MPa. The prototypes also included 0, 2, and 12 (or 8) total elastic sheets.

[0053] These all-solid-state batteries were subjected to confining pressures of 1.0 MPa and 3.0 MPa using a pressure mechanism, and the variations in pressure acting on the upper (outer) negative electrode of the first electrode stack and the upper negative electrode of the third electrode stack were measured. To measure the variations in pressure, a 12 x 44 grid was set on the negative electrode, the pressure acting on each grid was measured, and the standard deviation was calculated as a value indicating the variations in pressure, which was then normalized as a percentage of the confining pressure.

[0054] Figure 4 shows the pressure variation when an elastic sheet with a Young's modulus of 18.5 MPa is used and the confining pressure is set to 1.0 MPa, Figure 5 shows the pressure variation when an elastic sheet with a Young's modulus of 18.5 MPa is used and the confining pressure is set to 3.0 MPa, Figure 6 shows the pressure variation when an elastic sheet with a Young's modulus of 29.4 MPa is used and the confining pressure is set to 1.0 MPa, and Figure 7 shows the pressure variation when an elastic sheet with a Young's modulus of 29.4 MPa is used and the confining pressure is set to 3.0 MPa.

[0055] In both cases, when there were two elastic sheets, the pressure variation was smaller than when there were no elastic sheets, and it was confirmed that even when there were 12 elastic sheets, the pressure variation was almost the same as when there were two elastic sheets. [Explanation of symbols]

[0056] 1 All-solid-state battery 10 Electrode laminate 11 Positive electrode layer 111 Positive electrode current collector 112 Cathode active material layer 12 negative electrode layer 121 Negative electrode current collector 122 Negative electrode active material layer 13 Solid electrolyte layer 131 First solid electrolyte layer 132 Second solid electrolyte layer 20 Elastic Sheet 30 Exterior body 41 Positive electrode tab 42 tabs M Battery Module P pressure mechanism

Claims

1. a plurality of electrode stacks each 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; and an elastic sheet disposed between the electrode stacks; some of the plurality of electrode stacks directly contact the adjacent electrode stacks; The elastic sheet has a Young's modulus of 30 MPa or less.

2. The all-solid-state battery according to claim 1 , wherein the number of the elastic sheets is two or more and less than half the number of the electrode laminates.

3. 3. The all-solid-state battery according to claim 1, wherein the elastic sheet has a Young's modulus of 15 MPa or more and 20 MPa or less.

4. a pressure mechanism that applies a constraining pressure to constrain the all-solid-state batteries in a thickness direction; The battery module, wherein the restraining pressure applied by the pressurizing mechanism is 3.0 MPa or less.

5. The battery module according to claim 4 , wherein the pressure applied by the pressure mechanism is 0.5 MPa or more and 2.0 MPa or less.

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