Battery module and spacer used for battery module

Abstract

To reduce leakage of an electrolyte from an electrode body in a battery in a battery module.SOLUTION: A battery module 100 comprises a plurality of batteries disposed side by side in a predetermined direction, a binding member 110 which binds the plurality of batteries in the predetermined direction, and a spacer 120 which is disposed between adjacent batteries in the plurality of batteries. The plurality of batteries include: a case 10 having a pair of opposed long side faces in the predetermined direction of arrangement; an electrode body which is stored in the case 10; and an electrolyte. The spacer 120 is disposed between opposed side faces of the adjacent batteries. On a surface of the spacer 120, an uneven pattern is provided for making the electrolyte in the battery harder to flow from a central part to the outside of the battery than in a case where the electrolyte flows from the outside to the central part when pressed against the opposed side faces of the adjacent batteries.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a battery module and a spacer used in the battery module. [Background technology]

[0002] When a battery is repeatedly charged and discharged, the internal electrode body expands. This expansion of the electrode body can cause the electrolyte impregnated in the electrode body to be pushed out. For example, Japanese Patent Application Laid-Open No. 2022-128030 discloses a pair of secondary batteries arranged adjacent to each other and a spacer arranged between the secondary batteries. This spacer ensures an appropriate restraining force of the electrode body by the case, thereby suppressing the discharge of electrolyte caused by repeated charging and discharging.

[0003] Furthermore, Japanese Patent Application Laid-Open Publication No. 2017-126430 discloses a spacer having a wavy cross-sectional shape in which protrusions protruding toward a first battery cell and protrusions protruding toward a second battery cell are alternately repeated. The wavy cross-sectional shape of the spacer is formed by the first to sixth protrusions, and the fifth and sixth protrusions come into contact with the battery cell when the battery cell expands. This spacer allows a certain load or more to be applied to the battery cell.

[0004] Japanese Patent Application Laid-Open Publication No. 2018-32581 discloses a battery pack in which multiple rectangular battery cells and multiple spacers are alternately stacked in the thickness direction. Multiple comb-shaped ribs are formed on the surface of the spacers and contact the battery cells. The gaps between the ribs function as flow paths for the refrigerant. Furthermore, ribs are provided to press down on both ends and the top of the battery cells in the width direction, preventing electrolyte leakage from the electrode assembly. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-128030 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-126430 [Patent Document 3] Japanese Patent Application Publication No. 2018-32581 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, when a battery swells, the center of the wide side of the case is most likely to swell. In the technology described in JP 2022-128030 A, when a load is applied from the spacer to the secondary battery, a biased confining pressure may occur at the center of the wide side of the case. This tends to concentrate the load near the center of the electrode assembly, causing the electrolyte to be expelled to the outside. In addition, in the technology described in JP 2017-126430 A, the electrode assembly is pressed along the wavy shape, so confining pressure is likely to be applied to the area where the battery cell and the protrusions are in contact. Furthermore, the confining pressure is weaker in the grooves that are not in contact with the protrusions, making it easier for the electrolyte to be pushed out along the grooves. In the technology described in JP 2018-32581 A, spacers are used to press both ends and the top of the battery cell in the width direction, thereby preventing electrolyte leakage. However, the grooves provided at both ends as flow paths for the refrigerant and the bottom are not restricted. Therefore, the electrolyte pushed out by the confining pressure is likely to escape into the grooves or the lower part, leaving room for improvement. If the electrolyte is pushed out from the electrode body, there is a risk of uneven liquid distribution inside the battery. Furthermore, when there is uneven liquid distribution, the concentration distribution of charge carriers inside the electrode body becomes uneven. As a result, there is a risk of a shortage of charge carriers inside the electrode body, which may lead to battery performance degradation (so-called high-rate degradation).

[0007] Therefore, the present disclosure has been made in consideration of these points, and aims to provide a battery module that does not hinder the intrusion of electrolyte from the outside to the inside of the electrode body and reduces leakage of electrolyte from the electrode body. [Means for solving the problem]

[0008] The battery module disclosed herein includes a plurality of batteries arranged in a predetermined direction, a restraining member that restrains the plurality of batteries in the predetermined direction, and a spacer disposed between adjacent batteries of the plurality of batteries. The plurality of batteries include a case having a pair of opposing side surfaces facing the predetermined arrangement direction, an electrode assembly housed in the case, and an electrolyte. The spacer is disposed between the opposing side surfaces of the adjacent batteries. The surface of the spacer is provided with an uneven pattern that, when pressed against the opposing side surfaces of the adjacent batteries, makes it more difficult for the electrolyte in the batteries to flow from the center to the outside than from the outside to the center.

[0009] In this battery module, when the battery expands, the uneven pattern on the spacer surface is pressed against the long side of the battery case. This transfers the uneven pattern to the electrode body inside the battery. This uneven pattern is designed to make it more difficult for the electrolyte to flow from the center of the battery to the outside than from the outside to the center. This reduces the amount of electrolyte pushed out of the electrode body due to the expansion of the electrode body. This effect reduces the occurrence of uneven electrolyte and suppresses uneven distribution of charge carrier concentration inside the electrode body. This makes the charge carriers uniform inside the electrode body and suppresses performance degradation of the battery cell (so-called high-rate degradation). [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a battery according to one embodiment disclosed herein. [Figure 2] FIG. 2 is a longitudinal cross-sectional view of a battery according to one embodiment disclosed herein. [Figure 3] FIG. 3 is an exploded view that schematically shows the configuration of a wound electrode body of a battery according to one embodiment disclosed herein. [Figure 4] FIG. 4 is a perspective view of a battery module according to one embodiment disclosed herein. [Figure 5]FIG. 5 is a cross-sectional view of a battery module according to one embodiment disclosed herein. [Figure 6] FIG. 6 is a schematic plan view of a spacer according to one embodiment disclosed herein. [Figure 7] FIG. 7 is an explanatory diagram for explaining the concave-convex pattern of a spacer according to one embodiment disclosed herein. [Figure 8] FIG. 8 is an explanatory diagram for explaining the concave-convex pattern of a spacer according to another embodiment. [Figure 9] FIG. 9 is an explanatory diagram for explaining the concave-convex pattern of a spacer according to another embodiment. [Figure 10] FIG. 10 is an explanatory diagram for explaining the concave-convex pattern of a spacer according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Terminology> A typical embodiment of a battery module according to the present disclosure will be described in detail below with reference to the drawings. Matters necessary for implementation other than those specifically mentioned in this specification (e.g., the general configuration and manufacturing process of a battery that do not characterize the present disclosure) can be understood as design matters of a person skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. In the following drawings, components and parts that perform the same function are denoted by the same reference numerals. Furthermore, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships.

[0012] In this specification, the term "battery" encompasses primary batteries, reusable storage batteries (secondary batteries), and storage elements in general. Examples of secondary batteries include lithium ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries. Hereinafter, this embodiment will be described using a lithium ion secondary battery, which is a typical battery, as an example. In addition, in this specification, the term "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as a charge carrier and achieves repeated charging and discharging by the transfer of charge associated with the lithium ions between the positive and negative electrodes.

[0013] In this specification, when a numerical range is described as "A to B (where A and B are any numerical values)," it means "A or more and B or less," and also encompasses the meanings of "greater than A and less than B," "greater than A and B or less," and "greater than A and less than B."

[0014] <Battery> A lithium-ion secondary battery 1 according to this embodiment includes a case 10, a wound electrode assembly 20 housed in the case 10, and an electrolyte. FIG. 1 is a perspective view of the lithium-ion secondary battery 1 according to one embodiment. FIG. 2 is a schematic longitudinal cross-sectional view of the lithium-ion secondary battery 1 taken along line II-II in FIG. 1. In FIG. 2, a portion of the wound electrode assembly 20 is shown in a see-through manner so that the configuration of the wound electrode assembly 20 can be seen. In the following description, the symbols L, R, U, and D in the drawings represent the left, right, top, and bottom of the lithium-ion secondary battery 1. The symbol T in the drawings represents the thickness direction of the lithium-ion secondary battery 1. However, these directions are merely provided for the sake of convenience and do not limit the installation form of the lithium-ion secondary battery 1 in any way.

[0015] <Case> The case 10 is a case that mainly houses the wound electrode assembly 20, an electrolyte (not shown), and the like. As shown in FIG. 1 , in the lithium-ion secondary battery 1 according to this embodiment, the case 10 has a hexahedral box shape. More specifically, the case 10 has a rectangular parallelepiped shape, and is a flattened square shape. The case 10 includes a case main body 11 that houses the wound electrode assembly 20 and the electrolyte (not shown), and a sealing plate (lid) 12 that seals the opening of the main body 11. The main body 11 and the sealing plate 12 are welded and sealed (hermetically sealed) by laser welding or the like.

[0016] The material of the case 10 is not particularly limited as long as it is the same as that used in conventional batteries of this type. For example, the material of the case 10 may be a lightweight metal material with good thermal conductivity, such as aluminum or an aluminum alloy. The thickness of the case 10 is not particularly limited as long as the effects of the technology of the present disclosure are achieved. From the viewpoint of improving the strength of the lithium-ion secondary battery 1, the lower limit of the thickness of the case 10 is preferably 0.2 mm or more, more preferably 0.3 mm or more, and even more preferably 0.4 mm or more. Furthermore, from the viewpoint of transferring the concave-convex pattern of the spacer 120 (described later) to the surface of the electrode assembly, the upper limit of the thickness of the case 10 may be 2 mm or less, preferably 1.5 mm or less, more preferably 1 mm or less, and even more preferably 0.8 mm or less. The configuration of the case 10 can also be modified. For example, a flexible laminate film may be used as the case.

[0017] The case 10 is provided with a safety valve 13 and a liquid inlet (not shown). The safety valve 13 is a thin-walled valve that is configured to release the internal pressure of the case 10 when the internal pressure rises above a predetermined level. The liquid inlet is a hole for injecting the electrolyte. The liquid inlet is no longer needed after the electrolyte is injected, and can be sealed by laser welding or the like. Alternatively, the liquid inlet can be sealed by attaching a plug. In this embodiment, the main body 11 of the case 10 is composed of a bottom wall 11a, a pair of long side surfaces 11b1 and 11b2 extending from the bottom wall 11a and facing each other, and a pair of short side surfaces 11c1 and 11c2. Here, the safety valve 13 and the liquid inlet are provided in the sealing plate 12.

[0018] A positive electrode external terminal 14 and a negative electrode external terminal 15 for external connection are provided in an exposed state on the outside of the case 10. These electrode terminals are electrically connected to a wound electrode body 20 housed in the case 10 via internal terminals 16 and 17. The external terminals 14 and 15 are made of metal. For example, aluminum or an alloy mainly containing aluminum can be used as the positive electrode external terminal 14. For example, copper or a copper alloy can be used as the negative electrode external terminal 15.

[0019] The internal terminals 16, 17 are made of metal. For example, aluminum or an aluminum alloy may be used as the positive electrode internal terminal 16 from the viewpoint of improving the bonding strength with the positive electrode tab 31c (or the portion 31a where the positive electrode active material layer is not formed). For example, copper or a copper alloy may be used as the negative electrode internal terminal 17 from the viewpoint of improving the bonding strength with the negative electrode tab 41c (or the portion 41a where the negative electrode active material layer is not formed).

[0020] In this embodiment, the external terminals 14, 15 are attached to the surface 60a (outside) of the sealing body 60 via a gasket 18. The internal terminals 16, 17 are attached to the back surface (inside) of the sealing plate 12 via an insulator 19. The materials of the gasket 18 and the insulator 19 are not particularly limited. Materials with excellent chemical resistance and weather resistance can be used for the gasket 18 and the insulator 19. For example, resins such as tetrafluoroethylene-polyfluoroalkyl vinyl ether copolymer (PFA), polyethylene (PE), polypropylene (PP), and polyphenylene sulfide (PPS) can be used for the gasket 18 and the insulator 19.

[0021] <Electrolyte> The electrolyte can be a non-aqueous electrolyte prepared by dissolving a supporting salt in a suitable non-aqueous solvent. Conventional non-aqueous electrolytes can be used without any particular limitations. Examples of non-aqueous solvents include carbonates, ethers, esters, sulfones, and lactones. Among these, carbonates are preferred from the viewpoint of improving battery performance. Examples of carbonates that can be used include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). These solvents can be used alone or in combination of two or more.

[0022] <Electrode body> The positive electrode 30 and the negative electrode 40 of the lithium ion secondary battery 1 according to this embodiment have active material layers 32, 42. The positive electrode 30 includes a positive electrode current collector foil 31 and a positive electrode active material layer 32. The negative electrode 40 includes a negative electrode current collector foil 41 and a negative electrode active material layer 42. Separators 50a, 50b are interposed between the positive electrode 30 and the negative electrode 40.

[0023] The electrode body has a laminated structure in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween. As shown in FIG. 3, in this embodiment, the electrode body is a wound electrode body 20 in which a rectangular positive electrode 30 and a negative electrode 40 are wound with rectangular separators 50a and 50b interposed therebetween. FIG. 3 is an exploded view schematically showing the configuration of the wound electrode body 20 according to this embodiment. FIG. 3 also shows a schematic diagram of a cell unit constituting the wound electrode body 20. In the following description, the symbols LR, T, and UD in the drawings represent the width direction, thickness direction, and height direction of the wound electrode body 20. As shown in FIGS. 1 and 2, the wound electrode body 20 is housed between a pair of opposing side surfaces (e.g., long side surface 11b1 and long side surface 11b2) of the case 10, with the positive electrode 30 and the negative electrode 40 laminated with separators 50a and 50b interposed therebetween. However, the electrode body is not limited to this, and may be a laminated electrode body in which positive electrodes and negative electrodes are alternately stacked with separators interposed therebetween. There is no particular limitation on the number of wound electrode bodies 20. The case 10 may house a plurality of electrode bodies (for example, a plurality of the above-mentioned cell units stacked in the thickness direction).

[0024] <Positive electrode and positive electrode active material layer> As shown in FIG. 3 , the positive electrode 30 includes a rectangular positive electrode current collector foil 31 and a positive electrode active material layer 32 formed on the surface of the positive electrode current collector foil 31. The positive electrode active material layer 32 contains a positive electrode active material that can reversibly store and release charge carriers (e.g., lithium ions), i.e., release charge carriers during charging and store charge carriers during discharging. The positive electrode active material layer 32 may be formed on one or both sides (both sides in this example) of the positive electrode current collector foil 31. As shown in FIGS. 2 and 3 , the positive electrode 30 may have a positive electrode active material layer-free portion 31a where the positive electrode active material layer 32 is not formed and the positive electrode current collector foil 31 is exposed. The positive electrode active material layer-free portion 31a is provided at one end of the wound electrode body 20. In this embodiment, a plurality of positive electrode tabs 31c are provided intermittently at predetermined positions along the longitudinal direction of the positive electrode 30 in the portion 31a where the positive electrode active material layer is not formed. Each of the positive electrode tabs 31c protrudes in the width direction of the wound electrode body 20. The positive electrode tabs 31c are provided at predetermined positions so that they are aligned in the wound state. A positive electrode internal terminal 16 can be joined to the positive electrode tabs 31c. Also, in this embodiment, a positive electrode protective layer 31b is provided on the edge of the positive electrode active material layer 32 on the positive electrode current collector foil 31 (more specifically, on the portion 31a where the positive electrode active material layer is not formed). The positive electrode protective layer 31b is a layer that protects the portion 31a where the positive electrode active material layer is not formed and may be a layer containing an inorganic filler (e.g., alumina, etc.).

[0025] The material of the positive electrode current collector foil 31 is not particularly limited and may be any known positive electrode current collector foil 31 used in batteries. The material of the positive electrode current collector foil 31 is, for example, aluminum or an aluminum alloy. The positive electrode active material of the positive electrode active material layer 32 may be a positive electrode active material used in the positive electrode of a general lithium ion secondary battery. Specifically, the positive electrode active material is a lithium composite metal oxide having a layered rock salt structure, a spinel structure, an olivine structure, or the like. Examples of lithium composite metal oxides include LiCoO2, LiNiO2, LiFeO2, and LiNi x Co y Mn 1-x-y O2(NCM), LiNi 0.5 Mn 1.5 O4, LiNi0.8 Co 0.15 Al 0.05 Examples of the positive electrode active material include LiCrO2 (NCA), LiCrMO4, LiMn2O4, and LiFePO4 (LFP). These positive electrode active materials may be used singly or in combination of two or more. Among these, NCM is preferred as the positive electrode active material from the viewpoint of improving the cycle characteristics of the battery. The positive electrode active material layer 32 may contain various additives such as a binder, a conductive additive, an inorganic filler, or a thickener.

[0026] <Negative electrode and negative electrode active material layer> As shown in FIG. 3 , the negative electrode 40 includes a rectangular negative electrode current collector foil 41 and a negative electrode active material layer 42 formed on the surface of the negative electrode current collector foil 41. The negative electrode active material layer 42 contains a negative electrode active material that can reversibly store and release charge carriers (e.g., lithium ions), i.e., that can store charge carriers during charging and release charge carriers during discharging. The negative electrode active material layer 42 may be formed on one or both sides (both sides in this example) of the negative electrode current collector foil 41. As shown in FIGS. 2 and 3 , the negative electrode 40 may have a negative electrode active material layer-free portion 41a where the negative electrode active material layer 42 is not formed and the negative electrode current collector foil 41 is exposed. The negative electrode active material layer-free portion 41a is provided at one end of the wound electrode body 20. In this embodiment, a plurality of negative electrode tabs 41c are provided intermittently at predetermined positions along the longitudinal direction of the negative electrode 40 in the negative electrode active material layer non-forming portion 41a. Each of the plurality of negative electrode tabs 41c protrudes in the width direction of the wound electrode body 20. The plurality of negative electrode tabs 41c are provided at predetermined positions so that they are aligned in a wound state. A negative electrode internal terminal 17 can be joined to the negative electrode tabs 41c.

[0027] The material of the negative electrode current collector foil 41 may be a known negative electrode current collector foil used in batteries, and is not particularly limited. The material of the negative electrode current collector foil 41 is, for example, copper or a copper alloy. The negative electrode active material of the negative electrode active material layer 42 may be a negative electrode active material used in the negative electrodes of general lithium-ion secondary batteries. Specific examples of the negative electrode active material include carbon materials such as soft carbon (easily graphitizable carbon), amorphous carbon materials, graphite, hard carbon (non-graphitizable carbon), and carbon nanotubes; metal oxide materials such as silicon oxide, titanium oxide, vanadium oxide, and lithium-titanium composite oxide; metal nitride materials such as lithium nitride and lithium-cobalt composite nitride; and silicon compounds. These negative electrode active materials may be used alone or in combination of two or more. Of these, graphite is preferred as the negative electrode active material 42 from the viewpoint of improving energy density. The negative electrode active material layer 42 may contain various additives such as a binder, a conductive additive, an inorganic filler, or a thickener.

[0028] <Separator> The separators 50a and 50b according to this embodiment are porous insulating sheets. However, the shape and dimensions of the separators 50a and 50b are not particularly limited and may be determined appropriately depending on the battery design. Typically, the separators 50a and 50b insulate the positive electrode 30 and the negative electrode 40, and therefore the dimensions of the separators 50a and 50b are larger than those of the positive electrode 30 and the negative electrode 40. The material of the separators 50a and 50b may be any known separator used in batteries and is not particularly limited. For example, resins such as polyolefins (e.g., polyethylene or polypropylene), polyesters, cellulose, or polyamides are preferably used as the material for the separator 50. Furthermore, the surfaces of the separators 50a and 50b may be provided with a heat-resistant layer as long as it does not significantly impair the effects of the technology disclosed herein.

[0029] As shown in FIG. 3, the width Ln of the negative electrode active material layer 42 is formed wider than, for example, the width Lp of the positive electrode active material layer 32. The widths Ls of the separators 50a and 50b are formed wider than the negative electrode active material layer 42. That is, as shown in FIG. 3, Lp < Ln < Ls. The positive electrode 30, the first separator 50a, the negative electrode 40, and the second separator 50b are aligned in the length direction and are stacked and wound in order. Here, the negative electrode active material layer 42 covers the positive electrode active material layer 32 with the separators 50a and 50b interposed therebetween. The negative electrode active material layer 42 is covered with the separators 50a and 50b. The positive electrode tab 31c of the positive electrode current collector foil 31 and the negative electrode tab 41c of the negative electrode current collector foil 41 are provided so as to protrude from the separators 50a and 50b in opposite directions in the width direction. The positive electrode protective layer 31b faces the edge of the negative electrode 40 on the side opposite to the side where the negative electrode tab 41c is provided via the separators 50a and 50b. As shown in FIG. 2, the wound electrode body 20 is in a flat state along a plane 21 including a winding axis WL (see FIG. 3) so as to be accommodated in the case 10. The wound electrode body 20 is accommodated such that the plane 21 abuts on the long side surface 11b1 or the long side surface 11b2 from the inside of the case 10. The positive electrode tab 31c protrudes from one of the laminated surfaces 22. Also, the negative electrode tab 41c protrudes from the other of the laminated surfaces 22. Along the winding axis WL, the positive electrode tab 31c is disposed on one side and the negative electrode tab 41c is disposed on the opposite side.

[0030] <Battery module> The battery module 100 disclosed herein includes a plurality of batteries (here, lithium-ion secondary batteries 1). The plurality of lithium-ion secondary batteries 1 are arranged in a predetermined direction. FIG. 4 is a perspective view of the battery module 100 according to one embodiment disclosed herein. In FIG. 4, the near side of the predetermined direction T is defined as the front (F), and the far side is defined as the rear (Rr). That is, the front of the battery module 100 is defined as F, and the rear is defined as Rr. Here, the predetermined direction T is the thickness direction T of the lithium-ion secondary batteries 1 (or the thickness direction T of the wound electrode body 20) and is also the stacking direction of the lithium-ion secondary batteries 1. In this specification, the term "battery module" refers to an assembly of batteries in which a plurality of batteries are arranged and electrically connected. In this embodiment, lithium-ion secondary batteries 1 are used as the batteries, but nickel-metal hydride batteries, etc. may also be used.

[0031] As shown in FIG. 4 , the battery module 100 includes a plurality of lithium-ion secondary batteries 1, a restraining member 110 that restrains the plurality of lithium-ion secondary batteries 1 in a predetermined direction T, and a spacer 120 disposed between adjacent lithium-ion secondary batteries 1. In this embodiment, the lithium-ion secondary batteries 1 are disposed such that the long side surface 11b1 of one lithium-ion secondary battery 1 and the long side surface 11b2 of the second lithium-ion secondary battery 1 alternately face each other. That is, the lithium-ion secondary batteries 1 are disposed such that the orientations of the lithium-ion secondary batteries 1 are alternated so that the positive electrode external terminals 14 and the negative electrode external terminals 15 are arranged alternately. In addition, the positive electrode external terminal 14 of one adjacent lithium-ion secondary battery 1 and the negative electrode external terminal 15 of the other adjacent lithium-ion secondary battery 1 are electrically connected to each other by a metal bus bar (not shown). However, this does not limit the arrangement or connection of the lithium-ion secondary batteries 1. The lithium-ion secondary batteries 1 may be connected in series or in parallel.

[0032] <Restraining member> The restraining member 110 restrains the plurality of lithium-ion secondary batteries 1 in a predetermined direction T. The restraining member 110 is configured to apply a predetermined restraining pressure to the plurality of lithium-ion secondary batteries 1 and the plurality of spacers 120 in the stacking direction of the electrode assembly. For example, as shown in FIG. 4 , the restraining member 110 is configured with a pair of end plates 112a and 112b, a pair of side plates 113a and 113b, and a bottom plate 111. Here, the plurality of lithium-ion secondary batteries 1 and the plurality of spacers 120 are housed inside the restraining member 110. The restraining member 110 may be a module case. However, the shape of the restraining member 110 is not limited to a box shape. For example, instead of the pair of side plates 113a and 113b, a bind bar or the like may be used to fasten the pair of end plates 112a and 112b. The restraining member 110 may also be a frame that restrains the plurality of lithium-ion secondary batteries 1 and the plurality of spacers 120.

[0033] The end plates 112a and 112b are disposed at the start and end points of the predetermined direction T, respectively. Here, as shown in FIG. 4 , the end plate 112a is disposed at the front F of the battery module 100. The end plate 112b is disposed at the rear Rr of the battery module 100. The side plates 113a and 113b support the short side surfaces 11c1 and 11c2 of the main body 11 of the lithium ion secondary battery 1 to arrange the lithium ion secondary batteries 1 along the predetermined direction T. In the restraint member 110, the pair of end plates 112a and 112b are bridged by the pair of side plates 113a and 113b. Here, the pair of end plates 112a and 112b and the pair of side plates 113a and 113b are connected by a plurality of screws 114. However, the method of connecting the end plates 112a and 112b and the side plates 113a and 113b is not limited to this. The end plates 112a, 112b and the side plates 113a, 113b can also be connected by adhesive, welding, or the like. In this embodiment, the plurality of lithium ion secondary batteries 1 and the plurality of spacers 120 are alternately arranged between the pair of end plates 112a, 112b (see FIG. 5). The plurality of lithium ion secondary batteries 1 and the plurality of spacers 120 are fixed between the pair of side plates 113a, 113b so as to be aligned along a predetermined direction T. This applies a restraining load to the plurality of lithium ion secondary batteries 1 and the plurality of spacers 120 from the predetermined direction T, thereby holding the battery module together. The bottom plate 111 is arranged so as to contact the bottom wall 11a of the main body 11 of the plurality of lithium ion secondary batteries 1.

[0034] The materials of the end plates 112a, 112b, the side plates 113a, 113b, and the bottom plate 111 are not particularly limited. These materials may be selected from metal, resin, and the like. From the viewpoints of the strength of the restraint member 110 and applying an appropriate load to the lithium-ion secondary battery 1 and the spacer 120, these materials are preferably metal. However, a portion of each member may be resin. Furthermore, the shapes of the end plates 112a, 112b, the side plates 113a, 113b, and the bottom plate 111 are not particularly limited as long as they do not significantly impair the effects of the technology of the present disclosure. In this embodiment, the end plates 112a, 112b, and the bottom plate 111 are rectangular and have a predetermined thickness (e.g., a thickness that allows multiple screws 114 to be driven in). Furthermore, the side plates 113a, 113b are formed thinner than the end plates 112a, 112b, and the bottom plate 111. 4, ribs 113c are provided at both ends of the pair of side plates 113a, 113b so as to protrude substantially perpendicularly and face each other. Here, these ribs 113c press down on the edges of the sealing plates 12 of the plurality of lithium ion secondary batteries 1 housed in the restraining member 110. In this way, the plurality of lithium ion secondary batteries 1 are held inside the restraining member 110.

[0035] The restraining member 110 restrains the plurality of lithium ion secondary batteries 1 and the plurality of spacers 120 while applying a predetermined restraining pressure. For example, the pair of end plates 112a, 112b are connected to the pair of side plates 113a, 113b by tightening the plurality of screws 114 so that the initial restraining pressure is approximately 0.05 MPa to 0.5 MPa before the batteries expand. The above initial restraining pressure can achieve a desirable restraining pressure (approximately 0.1 MPa to 2 MPa) after the batteries expand.

[0036] <Spacer> The spacers 120 are disposed between the opposing long side surfaces 11b1, 11b2 of the plurality of lithium ion secondary batteries 1 described above. Fig. 5 is a cross-sectional view of a battery module according to one embodiment disclosed herein. Fig. 5 is a cross-sectional view taken along line VV in Fig. 4, and schematically shows the arrangement of the lithium ion secondary batteries 1 and the spacers 120. As shown in Fig. 5, the plurality of lithium ion secondary batteries 1 and the plurality of spacers 120 are alternately disposed between a pair of end plates 112a, 112b.

[0037] The spacer 120 has the function of suppressing swelling of the lithium-ion secondary battery 1 while suppressing leakage of electrolyte from the wound electrode body 20 when a load is applied to the lithium-ion secondary battery 1. The spacer 120 also serves as a buffer material that protects the lithium-ion secondary battery 1 from shocks and vibrations from outside the battery module 100. The spacer 120 is also referred to as an inter-cell separator. The surface of the spacer 120 of the present disclosure is provided with an uneven pattern that, when pressed against the opposing long side surfaces 11b1, 11b2 of an adjacent lithium-ion secondary battery 1, makes it more difficult for electrolyte in the lithium-ion secondary battery 1 to flow from the center to the outside than from the outside to the center.

[0038] 6 is a schematic plan view of a spacer 120 according to one embodiment disclosed herein. In FIG. 6, a plan view seen from the long side surfaces 11b1 and 11b2 of the opposing lithium-ion secondary battery 1 is shown so that the shape of the surface of the spacer 120 can be seen. As shown in FIG. 6, the spacer 120 has a flat base portion 121. Furthermore, the spacer 120 is provided with a protrusion 122 that protrudes from the base portion 121 toward the long side surfaces 11b1 and 11b2 of the opposing lithium-ion secondary battery 1, and one or more recesses 123 formed by the protrusion 122.

[0039] The base portion 121 has a flat plate shape. The base portion 121 is, for example, rectangular. The base portion 121 is arranged between adjacent lithium ion secondary batteries 1. The base portion 121 prevents the lithium ion secondary batteries 1 from coming into direct contact with each other so that the side surfaces of the adjacent lithium ion secondary batteries 1 do not wear away. From the viewpoint of improving the energy density of the battery module 100, it is preferable that the thickness of the base portion 121 is equal to or thinner than the thickness of the protrusions 122.

[0040] The protrusions 122 are regions that abut against the side surfaces (long side surfaces 11b1 and 11b2) of the lithium-ion secondary battery 1. The protrusions 122 can apply a predetermined load to the portions that abut against the lithium-ion secondary battery 1. The protrusions 122 are formed to protrude substantially perpendicularly from the surface of the base portion 121 toward the long side surfaces 11b1 and 11b2 of the lithium-ion secondary battery 1. In this embodiment, as shown in FIG. 6 , multiple protrusions 122 are formed on the outer peripheral edge of one surface of the base portion 121. As a result, when the lithium-ion secondary battery 1 expands, the outer peripheral edge of the long side surface 11b1 or the long side surface 11b2 is pressed by the protrusions 122. In other words, a greater load is applied to the outer peripheral portion of the wound electrode body 20 in the lithium-ion secondary battery 1, preventing the impregnated electrolyte from leaking outward. Note that the protrusions 122 may be provided over the entire base portion 121 of the spacer 120.

[0041] The recesses 123 are grooves formed between the protrusions 122. Unlike the protrusions 122, the recesses 123 are also regions that do not abut against the long side surfaces 11b1 and 11b2 of the lithium-ion secondary battery 1. Therefore, the long side surface 11b1 or the long side surface 11b2 facing the recesses 123 is not pressed by the swelling of the lithium-ion secondary battery 1. Therefore, no load is applied to the wound electrode body 20 along the recesses 123. The recesses 123 can also be used as a flow path for flowing a refrigerant.

[0042] It is known that the electrode body inside a battery expands and contracts due to repeated charging and discharging, etc. This expansion of the electrode body can push out the electrolyte impregnated in the electrode body. It takes a certain amount of time for the pushed-out electrolyte to completely re-impregnate the electrode body. This causes uneven electrolyte (typically, uneven concentration distribution of charge carriers (e.g., lithium ions)) within the battery. As a result, there is a risk of a shortage of charge carriers inside the electrode body, which can lead to performance degradation of the battery cell (so-called high-rate degradation).

[0043] To prevent uneven battery liquid distribution, the inventors focused on spacers between batteries. The spacers are placed between batteries (or end plates, etc.). The spacers change thickness in response to battery swelling, thereby preventing the entire battery module from swelling. The expansion of the electrode assembly pushes the case from the inside, causing the battery to swell. When the battery swelling is small, the spacers can absorb the battery swelling by changing their thickness. Therefore, the electrolyte is less likely to be pushed out of the electrode assembly. Furthermore, when the electrode assembly contracts, the electrolyte is re-impregnated into the electrode assembly. However, battery swelling tends to gradually increase. Therefore, the reaction force from the battery spacers gradually increases, making it more difficult for the spacers to accommodate the battery swelling. This increases the force pressing against the battery, making it easier for the electrolyte to be pushed out of the electrode assembly and less likely to return to the electrode assembly. For example, with a conventional spacer with a flat surface, a uniform load is applied to the side of the battery case that abuts the spacer. In such a case, when the battery swells, the pressure tends to increase toward the center of the battery. Furthermore, the center of the expanded electrode body is also pressed strongly through the case. Therefore, the electrolyte is easily pushed out from the center of the electrode body and is difficult to return to the center. Furthermore, with a conventional spacer having striped recesses on its surface, the electrolyte is easily returned to the electrode body along the recesses, but the electrolyte is also easily pushed out along the recesses to the outside of the electrode body. The inventors provided a concave-convex pattern on the spacer 120 and adjusted the position where the pressure is applied to the side of the case 10 (more specifically, the flat surface of the electrode body).

[0044] The surface of the base portion 121 of the spacer 120 used in the battery module 100 disclosed herein is provided with an uneven pattern that, when pressed against the opposing long side surfaces 11b1 and 11b2 of an adjacent lithium-ion secondary battery 1, makes it more difficult for the electrolyte in the lithium-ion secondary battery 1 to flow from the center to the outside than from the outside to the center. The uneven pattern is formed by recesses 123 and protrusions 122. In this embodiment, the uneven pattern is provided on the surface (one side) of the spacer 120 facing the long side surface 11b1 (or long side surface 11b2) of the lithium-ion secondary battery 1. In this case, the uneven pattern is less likely to be reflected on the long side surface 11b2 (or long side surface 11b1) of the lithium-ion secondary battery 1 facing the opposite side to the one on which the uneven pattern is provided. In a preferred embodiment of the present disclosure, the uneven pattern is provided on both sides of the spacer 120. This makes it possible to more reliably reflect the uneven pattern on the lithium-ion secondary battery 1 facing the opposite side of the spacer 120.

[0045] FIG. 7 is an explanatory diagram illustrating the concave-convex pattern of a spacer according to one embodiment disclosed herein. FIG. 7 also schematically illustrates the flow of electrolyte when the long side surfaces 11b1 and 11b2 of the lithium-ion secondary battery 1 are pressed. Arrows A, B, and C in FIG. 7 indicate fluid flow. Arrow A indicates forward flow. Arrow B indicates reverse flow. Arrow C indicates the flow of fluid bounced back by the loop groove 123b. Note that in FIG. 7, the center of the spacer 120 is on the right side (forward direction P), and the flow approaches the outer edge of the spacer 120 toward the left side (reverse direction Q). Therefore, the shape of the recess 123 shown in FIG. 7 is formed so that the center of the long side surfaces 11b1 and 11b2 of the lithium-ion secondary battery 1 (more specifically, the wound electrode body 20) facing the spacer 120 is located on the left side. As shown in FIG. 7, the recess 123 is composed of a flow channel 123a and a loop groove 123b. The flow channel 123a is a channel through which fluid can flow without restriction in either the forward or reverse direction. Furthermore, fluid flowing in the loop groove 123b in the Q direction changes direction along the bound wall 122b (or by bouncing off). The loop groove 123b has the function of obstructing one direction of the flow in the flow channel 123a by turning back the flow of the fluid.

[0046] In this embodiment, the recess 123 is formed in a so-called Tesla valve shape. In this case, when the fluid flows in the Q direction in the figure (in other words, from the center to the outside of the electrode body), the fluid easily flows into the loop groove 123b. Therefore, the fluid that flows into the loop structure 123b collides with the inner wall (bound wall 123c) of the recess 123, circulates around the island protrusion 122a, and collides with the fluid flowing in the central flow channel 123a at the junction 124. Furthermore, when the fluid flows in the P direction in the figure (in other words, from the outside to the center of the electrode body), the fluid is less likely to flow into the loop groove 123b. As a result, the pressure loss in one direction (here, from the center to the outside of the wound electrode body 20) is significantly greater than the pressure loss in the other direction (here, from the outside to the center of the wound electrode body 20). Therefore, the electrolyte is less likely to flow from the center to the outside of the lithium-ion secondary battery 1 than when it flows from the outside to the center. Therefore, the electrolyte can be caused to flow preferentially toward the center of the wound electrode body 20. In other words, the electrolyte is prevented from flowing in the direction Q without being prevented from flowing in the direction P. In this specification, the term "Tesla valve" refers to a flow path pattern developed by Nikolaus Tesla.

[0047] A battery module 100 including the spacer 120 described above can reduce leakage of the electrolyte impregnated in the electrode assembly. The battery module 100 of the present disclosure includes a plurality of batteries arranged in a predetermined direction T, a restraining member 110 that restrains the plurality of batteries in the predetermined direction T, and a spacer 120 disposed between adjacent batteries among the plurality of batteries. The surface of the spacer 120 is provided with an uneven pattern. This uneven pattern is configured so that, when the spacer 120 is pressed against the long sides 11b1 and 11b2 of the battery, the electrolyte in the battery is less likely to flow from the center to the outside than from the outside to the center. Here, the spacer 120 is pressed against the long sides 11b1 and 11b2 of the main body 11 of the case 10 when the battery expands. As a result, the uneven pattern provided on the surface of the spacer 120 is transferred to the flat surface 21 of the electrode assembly (e.g., the wound electrode assembly 20) via the main body 11. Therefore, the electrolyte impregnated in the electrode body is more likely to flow along the uneven pattern transferred to the electrode body. Therefore, the electrolyte is less likely to flow from the center of the electrode body to the outside than from the outside to the center. Therefore, the impregnated electrolyte is prevented from being pushed outward from the electrode body. This prevents the electrolyte from penetrating from the outside to the inside of the electrode body and reduces leakage of the electrolyte from the inside to the outside of the electrode body. This effect reduces the occurrence of uneven electrolyte within the battery. This makes the charge carriers uniform within the electrode body, and suppresses battery performance degradation (so-called high-rate degradation).

[0048] The material of the spacer 120 is not particularly limited as long as it does not significantly impair the effects of the technology of the present disclosure. The spacer 120 may be made of metal or resin. However, from the viewpoint of safety, the spacer 120 preferably has insulating properties. Therefore, if the spacer 120 is made of metal, it is preferably coated with an insulating material. The spacer 120 is also preferably made of an elastic material. This can moderate the increase in the load applied by the spacer 120 when the battery swells due to charging and discharging. Therefore, from the viewpoint of more suitably achieving the above effects, the spacer 120 is preferably made of resin. Examples of materials for the spacer 120 include fluororesin, polyester resin, polyolefin resin, silicone resin, acrylic resin, chlorine resin, polysulfone (PSF), polystyrene (PS), polyimide, and polyamide resin. Furthermore, rubbers (thermosetting elastomers) can also be preferably used as the resin material for the spacer 120. Examples of fluororesins include polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer (ETFE), vinylidene fluoride (FKM), tetrafluoroethylene-propylene copolymer (FEPM), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (FFKM). Examples of polyolefin resins include PP, PE, and polymethylpentene (PMP). Examples of polyester resins include polyethylene terephthalate (PET). Examples of silicone resins include polydimethylsiloxane (PDMS). Examples of acrylic resins include polymethyl methacrylate (PMMA). Examples of chlorine resins include polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC). Examples of polyamide resins include nylon-6 and nylon-10.Examples of rubbers include natural rubber (NR), isoprene rubber (IR), styrene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), nitrile rubber (NBR), ethylene propylene rubber (EPDM), acrylic rubber (ACM), urethane rubber, silicone rubber, and epichlorohydrin rubber (ECO). Among these, PP is preferred as the material for the spacer 120 because it has a high compressive elastic modulus, making it easy to transfer the concave-convex pattern to the electrode body. The lower limit of the compressive elastic modulus of the spacer 120 may be 1 MPa or more, 10 MPa or more, preferably 20 MPa or more, more preferably 30 MPa or more, and even more preferably 40 MPa or more. The upper limit of the compressive elastic modulus of the spacer 120 may be 10 MPa or less, 20 MPa or less, preferably 30 MPa or less, more preferably 40 MPa or less, and even more preferably 50 MPa or less.

[0049] The thickness of the protrusions 122 is not particularly limited as long as it does not significantly impair the effects of the technology of the present disclosure. The protrusions 122 typically protrude by 1 mm or more from the surface of the spacer 120 toward the opposing long side surface 11b1 (or long side surface 11b2) of the lithium-ion secondary battery 1. The thickness of the protrusions 122 is preferably 2 mm or more, and more preferably 3 mm or more. This makes it easier to transfer the concave-convex pattern to the surface of the electrode assembly. From the viewpoint of the energy density of the battery module 100, the thickness of the protrusions 122 is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 5 mm or less. The thickness of the protrusions 122 is the depth of the recesses 123. The recesses 123 may be provided between the protrusions 122, or may be provided by cutting the base portion 121 or the protrusions 122.

[0050] The length and width of the recesses 123 are not particularly limited as long as they do not significantly impair the effects of the technology of the present disclosure. As shown in FIG. 6, multiple recesses 123 extend along the surface of the spacer 120 from the center of the spacer 120 to its outer edges. However, this is not limited to this, and the recesses 123 may be interrupted along the way. Alternatively, the recesses 123 may extend radially from the midpoint of the spacer 120. The width of the recesses 123 is the length of the recesses 123 in a direction perpendicular to the extension direction of the flow channel grooves 123a. Therefore, as shown in FIG. 7, the width W of the recesses 123 is the length sandwiched between the protrusions 122. The wider the width of the recesses 123, the easier it is to transfer the concave-convex pattern to the electrode body. The lower limit of the width of the recesses 123 is typically 1 mm or more, preferably 2 mm or more, more preferably 3 mm or more, and even more preferably 5 mm or more. Furthermore, the upper limit of the width of the recess 123 may be 20 mm or less, 15 mm or less, or 10 mm or less, from the viewpoint of fitting the layout of the groove pattern within the dimensions of the side surface of the battery.

[0051] As described above, the thinner the case 10, the easier it is to transfer the concave-convex pattern to the flat surface 21 of the wound electrode body 20 when the spacer 120 is pressed against the long side surfaces 11b1 and 11b2 of the lithium-ion battery 1. The greater the confining pressure of the confining member 110, the more strongly the spacer 120 is pressed against the long side surfaces 11b1 and 11b2, making it easier to transfer the concave-convex pattern. Furthermore, the higher the compressive elastic modulus of the spacer 120, the easier it is to transfer the concave-convex pattern. However, if the thickness of the case 10 is too small, the strength of the case 10 decreases. In this case, the case 10 or the confining member 110 becomes more susceptible to damage as the confining pressure increases or the compressive elastic modulus of the spacer 120 increases. When the case thickness is 0.1 mm to 0.9 mm and the compressive elastic modulus of the spacer 120 is 1 MPa to 20 MPa, the confining pressure is preferably 0.5 MPa to 2 MPa. When the thickness of the case is 1.0 mm or more, and the compressive elastic modulus of the spacer 120 is 20 MPa to 50 MPa, the confining pressure is preferably 0.1 MPa to 2 MPa. Furthermore, as the width W of the recess 123 increases, it becomes easier to transfer the concave-convex pattern to the plane 21 of the wound electrode body 20. When the width W of the recess 123 is 1 mm to 5 mm, the thickness of the case 10 is preferably 0.1 mm to 0.9 mm. Furthermore, when the width W of the recess 123 is 5 mm to 20 mm, the thickness of the case 10 is preferably 1 mm to 2 mm.

[0052] While the preferred embodiments of the present disclosure have been described above with reference to the accompanying drawings, such descriptions are not intended to be limiting and various modifications are possible.

[0053] <Other embodiments> FIG. 8 is an enlarged view of a main portion of a spacer according to another embodiment. FIG. 8 is a diagram illustrating an example of a concave-convex pattern. The concave-convex pattern shown in FIG. 8 is provided on the surface of the spacer, and when pressed against the opposing side surfaces of adjacent batteries, makes it more difficult for the electrolyte in the battery to flow from the center to the outside than from the outside to the center. In this embodiment, the concave-convex pattern is formed by recesses 223 and protrusions 222. As shown in FIG. 8, approximately V-shaped island protrusions 222a are provided between the recesses 223. When the electrolyte flows in the Q direction, it converges and accumulates at the side walls (bound walls 222b) of the island protrusions 222a, thereby obstructing the flow of the electrolyte. However, when the electrolyte flows in the P direction, it branches along the island protrusions 222a, so the flow of the electrolyte is not obstructed. The number of island protrusions 22a is not particularly limited.

[0054] FIG. 9 is an enlarged view of a main portion of a spacer according to another embodiment. FIG. 9 is a diagram illustrating an example of a concave-convex pattern. The concave-convex pattern shown in FIG. 9 is also provided on the surface of the spacer, making it more difficult for the electrolyte in the battery to flow from the center to the outside than from the outside to the center when pressed against the opposing side surfaces of an adjacent battery. In this embodiment, the concave-convex pattern is formed by recesses 323 and protrusions 322. As shown in FIG. 9, approximately C-shaped island protrusions 322a are provided between the recesses 323. When the electrolyte flows in the Q direction, it converges and accumulates at the side walls (bound walls 322b) of the island protrusions 322a, thereby impeding the flow of the electrolyte. However, when the electrolyte flows in the P direction, it branches off along the island protrusions 322a, so the flow of the electrolyte is not impeded. The number of island protrusions 322a is not particularly limited.

[0055] FIG. 10 is an enlarged view of a main portion of a spacer according to another embodiment. FIG. 10 is a diagram illustrating an example of a concave-convex pattern. The concave-convex pattern shown in FIG. 10 is also provided on the surface of the spacer, so that when the spacer is pressed against the opposing side surfaces of adjacent batteries, the electrolyte in the battery is less likely to flow from the center to the outside than from the outside to the center. In this embodiment, as shown in FIG. 10, the concave-convex pattern is formed by recesses 423, protrusions 422, and valves 422a. When the electrolyte flows in the Q direction, it collides with the side wall (bound wall 422b) of the valve 422a and turns back, thereby hindering the flow of the electrolyte. However, when the electrolyte flows in the P direction, it converges toward the center along the valve 422a, thereby facilitating the flow of the electrolyte. The number of valves 422a is not particularly limited.

[0056] Another aspect of the technology disclosed herein provides a spacer 120 disposed between adjacent batteries among a plurality of batteries. As described above, the surface of the spacer 120 is provided with a concave-convex pattern. The concave-convex pattern is configured such that, when pressed against an adjacent battery, electrolyte in the battery is less likely to flow from the center to the outside of the battery than from the outside to the center. This spacer 120 does not impede the intrusion of electrolyte from the outside to the inside of the electrode assembly, and can reduce leakage of electrolyte from the electrode assembly.

[0057] In the technology disclosed herein, each component and each process mentioned herein may be omitted or combined as appropriate, unless a particular problem arises. This specification also includes the disclosures described in the following sections.

[0058] Item 1: A battery module comprising: a plurality of batteries arranged in a predetermined direction; a restraining member that restrains the plurality of batteries in the predetermined direction; and a spacer arranged between adjacent batteries of the plurality of batteries, wherein the plurality of batteries comprise a case having a pair of opposing long sides facing the predetermined direction in which the batteries are arranged; an electrode body housed in the case; and an electrolyte; the spacer is arranged between the opposing long sides of the adjacent batteries, and the surface of the spacer is provided with an uneven pattern that, when pressed against the opposing long sides of the adjacent batteries, makes it more difficult for the electrolyte in the batteries to flow from the center to the outside than when it flows from the outside to the center.

[0059] Item 2: The battery module described in Item 1, wherein the spacer has a flat base portion, convex portions formed on the base portion, and concave portions formed between the convex portions, the concave-convex pattern is formed by the concave portions and the convex portions, and the concave portions obstruct one flow by turning back the flow of fluid.

[0060] Item 3: The battery module according to Item 1 or 2, wherein the concave-convex pattern has a Tesla bulb shape.

[0061] Item 4: The battery module according to any one of Items 1 to 3, wherein the case is made of aluminum or an alloy mainly containing aluminum.

[0062] Item 5: The battery module according to any one of Items 1 to 4, wherein the spacer is made of polypropylene.

[0063] Item 6: The battery module according to any one of Items 1 to 5, wherein the concave-convex pattern is provided on both sides of a spacer.

[0064] Item 7: A spacer to be placed in a battery, the surface of which is provided with an uneven pattern that makes it more difficult for electrolyte in the battery to flow from the center of the battery to the outside than from the outside to the center when the spacer is pressed against the battery. [Explanation of symbols]

[0065] 1. Lithium-ion secondary battery 10 cases 11 Main unit 11a Bottom wall 11b1, 11b2 long side 11c1, 11c2 short side 12 Sealing plate 13 Safety valve 14 Positive external terminal 15 Negative external terminal 16 Positive internal terminal 17 Negative internal terminal 18 Gasket 19 Insulator 20 Wound electrode body 21 plane 22 Laminated surface 30 positive electrode 31 Positive electrode current collector foil 31a Portion where positive electrode active material layer is not formed 31b Positive electrode protective layer 31c Positive electrode tab 32 Positive electrode active material layer 40 negative electrode 41 Negative electrode current collecting foil 41a Part where negative electrode active material layer is not formed 41c Negative electrode tab 42 Negative electrode active material layer 50a, 50b Separator 100 battery modules 110 Restraining member 111 Bottom Plate 112a, 112b end plates 113a, 113b side plates 113c Rib 114 Bis 120 spacer 121 Base 122 convex part 122a Island protrusion 122b Bound Wall 123 Recess 123a Flow channel 123b Loop groove 124 Confluence 220 Spacer 222 convex part 222a Island protrusion 222b Bound Wall 223 Recess 320 spacer 322 Convex part 322a Island protrusion 322b Boundary Wall 323 Recess 420 spacer 422 Convex part 422a Valve 423 Recess A arrow B arrow C arrow

Claims

1. A plurality of batteries arranged in a predetermined direction; a restraining member that restrains the plurality of batteries in the predetermined direction; a spacer disposed between adjacent batteries among the plurality of batteries; Equipped with The plurality of batteries a case having a pair of opposing side surfaces facing the aligned predetermined direction; an electrode assembly housed in the case and having a laminated structure in which a positive electrode and a negative electrode are laminated with a separator interposed between the pair of opposing side surfaces; an electrolyte solution contained in the case; Equipped with the spacer is disposed between opposing sides of the adjacent cells; The surface of the spacer is provided with an uneven pattern that makes it more difficult for the electrolyte in the battery to flow from the center to the outside than from the outside to the center when the spacer is pressed against the opposing side surfaces of the adjacent battery.

2. the spacer has a flat base portion, a convex portion formed on the base portion, and a concave portion formed between the convex portions, the concave-convex pattern is formed by the concave portions and the convex portions, The battery module according to claim 1 , wherein the recessed portion causes the fluid flow to turn back, thereby preventing one flow.

3. The battery module according to claim 2 , wherein the concave-convex pattern is in the shape of a Tesla bulb.

4. The battery module according to claim 1 , wherein the case is made of aluminum or an alloy mainly containing aluminum.

5. The battery module according to claim 1 , wherein the spacer is made of polypropylene.

6. The battery module according to claim 1 , wherein the concave-convex pattern is provided on both surfaces of a spacer.

7. A spacer disposed in a battery, The surface of the spacer is provided with an uneven pattern that makes it more difficult for the electrolyte in the battery to flow from the center of the battery to the outside than from the outside to the center when the spacer is pressed against the battery.

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