Battery module

Abstract

To provide a battery module that has high energy density, can prevent bending of a current collecting part of a battery cell, and can prevent deterioration and short-circuit due to the bending of the current collecting part of the battery cell.SOLUTION: A battery module 1 comprises: a plurality of battery cells 10 laminated in one direction; restraining bodies 20 restraining the plurality of battery cells 10 in a lamination direction; bus bars 30 connecting the battery cells 10 to each other; and bus bar holders 40 holding the bus bars 30. The bus bar holder 40 has a first expanding and contracting part 41 that follows the displacement in the lamination direction of the battery cell 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery module. [Background technology]

[0002] Conventionally, when stacking battery cells that expand and contract (for example, batteries that use lithium metal for the negative electrode) to form a battery module, it is known to place elastic members or springs between adjacent battery cells to absorb the expansion and contraction of the battery cells in order to secure the tab leads of the battery cells. It is also known to use expandable bus bars connecting adjacent battery cells (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-207442 Summary of the Invention [Problem to be solved by the invention]

[0004] However, placing elastic members or springs between adjacent battery cells takes up space within the battery module, reducing the overall energy density of the battery module and increasing its mass. Furthermore, even if elastic members or springs are placed between adjacent battery cells, the amount of expansion and contraction varies from battery cell to battery cell. This variation can cause stress in the tab leads of the battery cells, leading to deterioration and short circuits due to bending of the current collectors of the battery cells. Furthermore, the expansion and contraction of the busbars alone cannot prevent bending of the current collectors of the battery cells because the busbar holders that define the gaps between the busbars are fixed.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide a battery module that has a high energy density, suppresses bending of the current collecting parts of the battery cells, and can suppress deterioration and short circuits due to bending of the current collecting parts of the battery cells, thereby contributing to stabilizing battery performance, improving quality control in the manufacturing process, and ultimately improving energy efficiency. [Means for solving the problem]

[0006] [1] A plurality of battery cells stacked in one direction; a restraining body that restrains the plurality of battery cells in a stacking direction; a bus bar that connects the battery cells to each other; a bus bar holder that holds the bus bar, the bus bar holder has a first expansion / contraction portion that follows displacement of the battery cells in the stacking direction.

[0007] In the present invention, the busbar holder has a first expandable portion that follows the displacement of the multiple battery cells in the stacking direction, and there are no components that occupy space within the battery module, so the energy density of the entire battery module does not decrease and the mass of the battery module is prevented from increasing. Furthermore, as the battery cells expand and contract, the first expandable portion of the busbar holder expands and contracts to follow the displacement of the multiple battery cells in the stacking direction, so the first expandable portion can absorb the expansion and contraction of the battery cells and prevent deterioration and short circuits due to bending of the current collectors of the battery cells.

[0008] [2] The battery module according to [1], wherein an elastic member is disposed between the restraining body and the battery cell, or between the battery cells.

[0009] In the present invention, an elastic member is placed between the restraint and the battery cell, or between the battery cells, so that the elastic member can absorb the expansion and contraction of the battery cell, thereby suppressing deterioration and short circuits caused by bending of the collector parts of the battery cell.

[0010] [3] The battery module according to [1] or [2], wherein the bus bar has a second expansion / contraction section that follows the displacement of the battery cells in the stacking direction.

[0011] In the present invention, as the battery cells expand and contract, the second expandable portion of the busbar expands and contracts in accordance with the displacement of the multiple battery cells in the stacking direction, so that the second expandable portion can absorb the expansion and contraction of the battery cells and suppress deterioration and short circuits caused by bending of the battery cell collector parts.

[0012] [4] The battery module according to any one of [1] to [3], wherein the bus bar holder has rails that allow the bus bar to move in the stacking direction of the battery cells.

[0013] In the present invention, the bus bar holder has rails that allow the bus bar to move in the stacking direction of the battery cells, so that the bus bar can move along the rails as the battery cells expand and contract, thereby suppressing deterioration and short circuits caused by bending of the collector parts of the battery cells.

[0014] [5] The battery module according to any one of [1] to [4], wherein the negative electrode constituting the battery cell includes a material containing lithium metal or silicon.

[0015] In the present invention, even if the negative electrode constituting the battery cell contains a material containing lithium metal or silicon, as the battery cell expands and contracts, the first expandable portion of the busbar holder expands and contracts in accordance with the displacement of the multiple battery cells in the stacking direction, so that the first expandable portion can absorb the expansion and contraction of the battery cell and suppress deterioration and short circuits caused by bending of the battery cell's current collector.

[0016] [6] The battery module according to any one of [1] to [5], wherein the battery cells are solid-state batteries.

[0017] Even if the battery cells are solid-state batteries, the present invention allows for weight reduction because there are no components that occupy space within the battery module. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a battery module that has a high energy density, that can suppress bending of the current collector parts of the battery cells, and that can suppress deterioration and short circuits due to bending of the current collector parts of the battery cells. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram showing the configuration of a battery module according to a first embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing the configuration of a battery module according to a first embodiment of the present invention. [Figure 3] FIG. 4 is a schematic diagram showing the configuration of a battery module according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of a battery module according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a schematic diagram showing the configuration of a battery module according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a schematic diagram showing the configuration of a battery module according to a third embodiment of the present invention. [Figure 7] FIG. 10 is a schematic diagram showing the configuration of a battery module according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, a battery module according to one embodiment of the present invention will be described with reference to the drawings.

[0021] [Battery module] (First embodiment) 1 and 2 are schematic diagrams showing the configuration of a battery module according to a first embodiment of the present invention. Note that the drawings used in the following description may show characteristic parts enlarged for convenience in order to make the characteristics easier to understand, and the dimensional ratios of each component are not limited to those shown. As shown in FIGS. 1 and 2, a battery module 1 of this embodiment includes a plurality of battery cells 10, a restraining body 20, a bus bar 30, and a bus bar holder 40.

[0022] The multiple battery cells 10 are stacked in one direction (the horizontal direction in FIG. 1). The restraints 20 restrain the multiple battery cells 10 from both sides in the stacking direction (both sides in the horizontal direction in FIG. 1). The bus bars 30 connect adjacent battery cells 10 in the stacking direction of the multiple battery cells 10. The bus bar holders 40 are provided to extend in the stacking direction of the multiple battery cells 10, and hold the bus bars 30 from both sides in the longitudinal direction of the bus bars 30 (the direction perpendicular to the stacking direction of the multiple battery cells 10).

[0023] The bus bar holder 40 has a first expandable portion 41 that follows the displacement of the battery cells 10 in the stacking direction.

[0024] In the battery module 1 according to this embodiment, it is preferable that an elastic member 50 is disposed between the restraint 20 and the battery cells 10. This allows the elastic member 50 to absorb the expansion and contraction of the battery cells 10, and suppresses deterioration and short circuits caused by bending of the current collector parts of the battery cells 10.

[0025] "Battery cell" The battery cell in this embodiment has a positive electrode, a negative electrode, an electrolyte layer, and an exterior film. The battery cell is not particularly limited, but is preferably a solid-state battery. Even if the battery cell 10 is a solid-state battery, there is no component that occupies space within the battery module 1, making it possible to reduce the weight.

[0026] (positive electrode) The positive electrode is formed by laminating a first current collector layer and a first active material layer containing at least a positive electrode active material. In this embodiment, the positive electrode has the first current collector layer and the first active material layer formed on both main surfaces of the first current collector layer.

[0027] The first current collector layer is preferably made of at least one material with high electrical conductivity. Examples of highly conductive materials include metals or alloys containing at least one of silver (Ag), palladium (Pd), gold (Au), platinum (Pt), aluminum (Al), chromium (Cr), and nickel (Ni), as well as non-metals such as carbon (C). Considering both high conductivity and manufacturing costs, aluminum, nickel, and stainless steel are preferred. Furthermore, aluminum is less likely to react with the positive electrode active material and electrolyte. Therefore, using aluminum for the first current collector layer can reduce the internal resistance of the battery.

[0028] The first current collector layer may be in the form of, for example, a foil, a plate, a mesh, a nonwoven fabric, a foam, etc. In order to improve adhesion to the first active material layer, carbon or the like may be disposed on the surface of the first current collector layer, or the surface may be roughened.

[0029] The first active material layer contains a positive electrode active material that donates and receives lithium ions and electrons. The positive electrode active material is not particularly limited as long as it is a material that can reversibly release and absorb lithium ions and transport electrons, and known positive electrode active materials that can be used for the positive electrode of lithium ion batteries can be used. For example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), solid solution oxide (Li2MnO3-LiMO2 (M = Co, Ni, etc.)), lithium-manganese-nickel-cobalt oxide (LiNi x Mn y Co z O2, x+y+z=1), composite oxides such as olivine-type lithium phosphate (LiFePO4); conductive polymers such as polyaniline and polypyrrole; sulfides such as Li2S, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, and Li-Mo-S compounds; mixtures of sulfur and carbon; etc. The positive electrode active material may be composed of one kind of the above materials alone, or may be composed of two or more kinds.

[0030] The first active material layer contains an electrolyte that transfers lithium ions to and from the positive electrode active material. The electrolyte is not particularly limited as long as it has lithium ion conductivity, and materials commonly used in lithium ion batteries can be used. Examples of the electrolyte include inorganic solid electrolytes such as sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, and lithium-containing salts, polymer-based solid electrolytes such as polyethylene oxide, and gel-based solid electrolytes containing lithium-containing salts and lithium-ion conductive ionic liquids. Among these, sulfide solid electrolyte materials are preferred from the viewpoints of high lithium ion conductivity, good structural formability by pressing, and good interfacial bonding. The electrolyte may be composed of one kind of the above materials alone or two or more kinds of them. The electrolyte contained in the first active material layer may be the same material as the electrolyte contained in the second active material layer or the solid electrolyte layer, or may be a different material.

[0031] The first active material layer may contain a conductive additive to improve the conductivity of the positive electrode. The conductive additive may be any conductive additive generally used in lithium-ion batteries. Examples of the conductive additive include carbon black such as acetylene black and Ketjen black; carbon fiber; vapor-grown carbon fiber; graphite powder; and carbon materials such as carbon nanotubes. The conductive additive may be composed of one or more of the above materials.

[0032] The first active material layer may also contain a binder that functions to bind the positive electrode active materials together and between the positive electrode active material and the first current collector layer.

[0033] The first active material layer may be formed on both main surfaces of the first current collector layer, or on only one main surface of the first current collector layer. When the positive electrode is a single-sided coated electrode, a laminated positive electrode formed by stacking two positive electrodes with their current collector surfaces facing each other may be used as a double-sided coated electrode. When the first current collector layer has a three-dimensional porous structure such as a mesh, nonwoven fabric, or foam, the first current collector layer may be provided integrally with the first active material layer.

[0034] The first current collector layers are assembled at one end in the width direction of the all-solid-state battery. The first active material layer is in contact with the electrolyte layer and may contain sulfides contained in the electrolyte layer.

[0035] (Negative electrode) The negative electrode is formed by laminating a second current collector layer and a second active material layer containing at least a negative electrode active material. In this embodiment, the negative electrode has the second current collector layer and second active material layers formed on both main surfaces of the second current collector layer and containing a negative electrode active material and an electrolyte.

[0036] The second current collector layer contains at least copper (Cu). Like the first current collector layer, the second current collector layer may contain a material other than copper that has high conductivity. Examples of highly conductive materials other than copper include metals or alloys containing at least one of silver (Ag), palladium (Pd), gold (Au), platinum (Pt), chromium (Cr), and nickel (Ni), or non-metals such as carbon (C). Considering not only high conductivity but also manufacturing costs, nickel or stainless steel is preferred as the material other than copper. Furthermore, stainless steel is less likely to react with the positive electrode active material, negative electrode active material, and electrolyte. Therefore, using stainless steel for the second current collector layer can reduce battery manufacturing costs.

[0037] The second current collector layer may be in the form of, for example, a foil, a plate, a mesh, a nonwoven fabric, a foam, etc. In order to improve adhesion to the second active material layer, carbon or the like may be disposed on the surface of the second current collector layer, or the surface may be roughened.

[0038] The second active material layer contains a negative electrode active material that donates and accepts lithium ions and electrons. The negative electrode active material is not particularly limited as long as it is a material that can reversibly absorb and release lithium ions and transport electrons, and known negative electrode active materials that can be used for the negative electrode of a lithium ion battery can be used. Examples of such materials include carbonaceous materials such as natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; alloy-based materials mainly composed of tin, tin alloys, silicon, silicon alloys, gallium, gallium alloys, indium, indium alloys, aluminum, and aluminum alloys; conductive polymers such as polyacene, polyacetylene, and polypyrrole; metallic lithium; lithium titanium composite oxides (e.g., Li4Ti5O 12 These negative electrode active materials may be composed of one kind of the above materials alone, or two or more kinds of them.

[0039] The second active material layer contains an electrolyte that transfers lithium ions to and from the negative electrode active material. The electrolyte is not particularly limited as long as it has lithium ion conductivity, and materials generally used in lithium ion batteries can be used. Examples of the electrolyte include inorganic solid electrolytes such as sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, and lithium-containing salts, polymer-based solid electrolytes such as polyethylene oxide, and gel-based solid electrolytes containing lithium-containing salts and lithium-ion conductive ionic liquids. The electrolyte may be composed of one or more of the above materials. The electrolyte contained in the second active material layer may be the same as or different from the electrolyte contained in the first active material layer or the solid electrolyte layer.

[0040] The second active material layer may contain a conductive additive, a binder, etc. These materials are not particularly limited, and may be, for example, the same materials as those used in the first active material layer described above.

[0041] The second active material layer may be formed on both main surfaces of the second current collector layer, or on only one main surface of the second current collector layer. When the second current collector layer has a three-dimensional porous structure such as a mesh, nonwoven fabric, or foam, the second current collector layer may be provided integrally with the second active material layer.

[0042] The negative electrode may contain a material containing lithium metal or silicon. As shown in Figures 1 and 2, as the battery cells 10 expand and contract, the first expandable portion 41 of the bus bar holder 40 expands and contracts in accordance with the displacement of the battery cells 10 in the stacking direction. This allows the first expandable portion 41 to absorb the expansion and contraction of the battery cells 10 and suppress deterioration and short circuits caused by bending of the current collectors of the battery cells 10.

[0043] (electrolyte layer) The electrolyte layer is disposed between the first active material layer and the second active material layer.

[0044] The electrolyte is not particularly limited as long as it has lithium ion conductivity and insulating properties, and materials generally used in lithium ion batteries can be used. Examples include inorganic solid electrolytes such as sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, and lithium-containing salts, polymer-based solid electrolytes such as polyethylene oxide, and gel-based electrolytes containing lithium-containing salts and lithium ion-conductive ionic liquids. Among these, sulfide solid electrolyte materials are preferred from the viewpoints of high lithium ion conductivity, structural formability by pressing, and interfacial bonding. The form of the electrolyte material is not particularly limited, but may be, for example, in the form of particles.

[0045] The electrolyte layer may contain an adhesive to impart mechanical strength and flexibility.

[0046] The electrolyte layer may be in the form of a sheet having a porous substrate and a solid electrolyte supported on the porous substrate. The form of the porous substrate is not particularly limited, and examples thereof include woven fabric, nonwoven fabric, mesh cloth, porous membrane, expanded sheet, and punched sheet. Among these forms, nonwoven fabric is preferred from the viewpoint of handleability, which allows for a higher loading of solid electrolyte.

[0047] The porous substrate is preferably made of an insulating material, which can improve the insulation of the electrolyte layer. Examples of insulating materials include resin materials such as nylon, polyester, polyethylene, polypropylene, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyvinylidene chloride, polyvinyl chloride, polyurethane, vinylon, polybenzimidazole, polyimide, polyphenylene sulfite, polyether ether ketone, cellulose, and acrylic resin; natural fibers such as hemp, wood pulp, and cotton linter; and glass.

[0048] (exterior film) The exterior film accommodates an electrode stack including a positive electrode, a negative electrode, and an electrolyte layer, and includes, for example, a sealant resin layer, a metal layer, and an outer resin layer.

[0049] According to the battery module 1 of this embodiment, the bus bar holder 40 has the first expandable portion 41 that follows the displacement of the battery cells 10 in the stacking direction, and therefore there are no components that occupy space within the battery module 1, so there is no decrease in the energy density of the entire battery module 1 and it is possible to prevent the mass of the battery module 1 from increasing. Furthermore, as shown in Figures 1 and 2, as the battery cells 10 expand and contract, the first expandable portion 41 of the bus bar holder 40 expands and contracts to follow the displacement of the multiple battery cells 10 in the stacking direction, so that the first expandable portion 41 can absorb the expansion and contraction of the battery cells 10 and prevent deterioration and short circuits caused by bending of the current collectors of the battery cells 10.

[0050] (Second embodiment) 3 and 4 are schematic diagrams showing the configuration of a battery module according to a second embodiment of the present invention. In Fig. 3 and Fig. 4, the same components as those in the battery module shown in Fig. 1 and Fig. 2 are denoted by the same reference numerals, and the description thereof will be omitted.

[0051] As shown in FIGS. 3 and 4, the battery module 100 of this embodiment includes a plurality of battery cells 10, a restraining body 20, a bus bar 30, and a bus bar holder 40.

[0052] In the battery module 100 of this embodiment, elastic members 50 are arranged between the restraint body 20 and the battery cells 10, and elastic members 110 are arranged between the battery cells 10. As a result, as shown in Figures 3 and 4, the elastic members 50 and 110 can absorb the expansion and contraction of the battery cells 10, and deterioration and short circuits caused by bending of the current collector parts of the battery cells 10 can be suppressed.

[0053] (Third embodiment) Figures 5 and 6 are schematic diagrams showing the configuration of a battery module according to a second embodiment of the present invention. In Figures 5 and 6, the same components as those in the battery module shown in Figures 1 and 2 are denoted by the same reference numerals, and their description will be omitted.

[0054] As shown in FIGS. 5 and 6, the battery module 200 of this embodiment includes a plurality of battery cells 10, a restraining body 20, a bus bar 30, a bus bar holder 40, and an elastic member 50.

[0055] In the battery module 200 according to this embodiment, the bus bar holder 40 has a first expandable portion 41 that follows the displacement of the battery cells 10 in the stacking direction, and the bus bar 30 has a second expandable portion 31 that follows the displacement of the battery cells 10 in the stacking direction. As a result, as shown in Figures 5 and 6 , the first expandable portion 41 of the bus bar holder 40 and the second expandable portion 31 of the bus bar 30 expand and contract in accordance with the displacement of the multiple battery cells 10 in the stacking direction as the battery cells 10 expand and contract. This allows the first expandable portion 41 and the second expandable portion 31 to absorb the expansion and contraction of the battery cells 10, thereby suppressing deterioration and short circuits caused by bending of the current collectors of the battery cells 10.

[0056] (Fourth embodiment) Fig. 7 is a schematic diagram showing the configuration of a battery module according to a fourth embodiment of the present invention. In Fig. 7, the same components as those in the battery modules shown in Figs. 1 and 2 are denoted by the same reference numerals, and the description thereof will be omitted.

[0057] As shown in FIG. 7, the battery module 300 of this embodiment includes a plurality of battery cells (not shown), a restraining body (not shown), a bus bar 30, and a bus bar holder 40.

[0058] In the battery module 300 according to this embodiment, the bus bar holder 40 has rails 42 along which the bus bars 30 can move in the stacking direction of the battery cells 10. This allows the bus bars 30 to move along the rails 42 in accordance with the expansion and contraction of the battery cells 10, thereby suppressing deterioration and short circuits due to bending of the current collecting parts of the battery cells 10.

[0059] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims. [Explanation of symbols]

[0060] 1,100,200,300 battery modules 20 restraint body 30 Busbar 31 Second expansion section 40 Busbar holder 41 First expansion section 42 Rail 50,110 Elastic member

Claims

1. A plurality of battery cells stacked in one direction; a restraining body that restrains the plurality of battery cells in a stacking direction; a bus bar that connects the battery cells to each other; a bus bar holder that holds the bus bar, the bus bar holder has a first expandable portion that follows displacement of the battery cells in the stacking direction, the bus bar has a second expandable portion that follows displacement of the battery cells in the stacking direction; The bus bars and the bus bar holders are alternately connected to each other in the battery module.

2. The battery module according to claim 1 , wherein an elastic member is disposed between the restraining body and the battery cell, or between the battery cells.

3. The battery module according to claim 1 , wherein the bus bar holder has rails that allow the bus bars to move in the stacking direction of the battery cells.

4. The battery module according to claim 1 , wherein the negative electrodes constituting the battery cells include a material containing lithium metal or silicon.

5. The battery module according to claim 1 , wherein the battery cells are solid-state batteries.

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