battery pack

Abstract

To provide a battery pack whose restraining load is unlikely to be reduced even when a charge state is low and that can stably apply a restraining load to a secondary battery.SOLUTION: The battery pack includes a plurality of rectangular secondary batteries 100, a porous elastic member 200 arranged between the rectangular secondary batteries 100, and a restraining mechanism for applying a restraining load to the rectangular secondary batteries 100 and the porous elastic member 200. The porous elastic member 200 has a gas flow path 250 extending inwardly from an outer peripheral edge OE in a state of being assembled on the battery pack.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Conventionally, battery packs formed by electrically connecting multiple secondary batteries (single cells) have been widely used in vehicle drive power sources and the like to achieve higher output. Related prior art documents include Patent Documents 1 and 2. For example, Patent Document 1 discloses a battery pack including multiple secondary batteries arranged in a predetermined arrangement direction, sheet-like heat conduction suppressing members with heat insulating material disposed between adjacent secondary batteries in the arrangement direction, and a restraining mechanism that applies a restraining load to the multiple secondary batteries and the heat conduction suppressing members in the arrangement direction.

[0003] In Patent Document 1, the heat insulating material of the heat conduction suppressing member has a structure in which a porous material such as silica xerogel is supported between the fibers of a fiber sheet. The porous material has multiple communication holes that communicate with the outside. Therefore, when the multiple secondary batteries are restrained in the arrangement direction by the restraint mechanism, the heat conduction suppressing member is crushed and compressed in the arrangement direction while expelling air from inside the porous material. In other words, it undergoes elastic deformation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 061894 [Patent Document 2] Utility Model Registration No. 3191519 Summary of the Invention [Problem to be solved by the invention]

[0005] When a battery pack is in use, each of the secondary batteries constituting the battery pack is charged and discharged. When a secondary battery is charged, the electrode body inside the battery case expands, increasing the thickness of the secondary batteries in the arrangement direction. As a result, the load on the porous material increases, and the porous material is further compressed in the arrangement direction. This compression of the porous material prevents the secondary battery from being subjected to an excessive restraint load exceeding a predetermined value.

[0006] On the other hand, when a secondary battery is discharged, the electrode body inside the battery case shrinks, reducing the thickness of the secondary battery in the arrangement direction. However, according to the inventors' investigations, even if the thickness of the secondary battery decreases with discharge, the thickness of the porous material in the arrangement direction does not return, making it difficult to restore the battery to its original size. As a result, the restraint load during discharge becomes smaller than the desired value, and the secondary battery may not be sufficiently compressed. This tendency is particularly noticeable when the SOC (State of Charge) is 15% or less.

[0007] The present invention has been made in consideration of the above circumstances, and its main object is to provide a battery pack in which a restraint load is unlikely to decrease even when the state of charge is low, and in which a restraint load can be stably applied to secondary batteries. [Means for solving the problem]

[0008] The present inventors conducted extensive research into the cause of the porous material not regaining its thickness in the arrangement direction during low SOC states, such as during discharge, and discovered a new reason: the porous material is not properly absorbing air. Specifically, in the configuration of Patent Document 1, the porous material is tightly sandwiched between the sides of the secondary battery, and the porous material is barely exposed to the outside air. To restore its original thickness, the porous material needs to absorb gas. However, when the portion exposed to the outside air is small, as described above, the amount of air absorbed is insufficient, and the thickness does not return to its original state even when the restraining load is relaxed. This led to the creation of the present invention.

[0009] The present invention discloses a battery pack including a plurality of prismatic secondary batteries arranged in a predetermined arrangement direction, a porous elastic member arranged between adjacent prismatic secondary batteries in the arrangement direction, and a restraining mechanism that applies a restraining load to the plurality of prismatic secondary batteries and the porous elastic member in the arrangement direction. The porous elastic member has a plurality of communication holes that communicate with the outside and is configured to be elastically deformable in the arrangement direction by taking in or exhausting gas. The battery pack satisfies at least one of the following two configurations: (1) the porous elastic member has a gas flow path extending inward from its outer periphery when assembled in the battery pack; and (2) another member is further provided between the prismatic secondary batteries and the porous elastic member, and the other member has a gas flow path extending inward from its outer periphery on at least the surface that contacts the porous elastic member when assembled in the battery pack.

[0010] In the present invention, a gas flow path leading to the porous elastic member is ensured even when the secondary battery is assembled into a battery pack and a restraint load is applied. As a result, when the secondary battery contracts due to discharge or the like, gas (typically air) around the battery pack passes through the gas flow path and is relatively more easily taken into the porous elastic member than in the configuration disclosed in, for example, Patent Document 1. As a result, the porous elastic member expands appropriately and is more likely to return to its original size (particularly the thickness in the arrangement direction). Therefore, even when the secondary battery contracts, the prismatic secondary battery can be stably kept pressed, and a decrease in the restraint load of the battery pack can be suppressed. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view schematically illustrating a battery pack according to an embodiment; [Figure 2] FIG. 2 is a perspective view schematically showing the secondary battery of FIG. [Figure 3] FIG. 3 is a schematic vertical cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 2 is a perspective view schematically showing an electrode assembly attached to a sealing plate. [Figure 5] FIG. 2 is a perspective view schematically showing one electrode body. [Figure 6] FIG. 2 is a schematic diagram showing the configuration of an electrode body. [Figure 7] FIG. 3 is a plan view schematically showing the positional relationship between a prismatic secondary battery and a porous elastic member. [Figure 8] 2 is a partially enlarged top view of the main part of the battery pack of FIG. 1, showing a schematic top view of the prismatic secondary battery and the porous elastic member. FIG. [Figure 9] FIG. 8 is a view corresponding to FIG. 7 according to a first modified example. [Figure 10] FIG. 8 is a view corresponding to FIG. 7 according to a second modified example. [Figure 11] 7 according to a third modified example, and FIG. 8B is a cross-sectional view taken along line (b)-(b) of FIG. [Figure 12] 8(A) is a plan view schematically showing the positional relationship between a prismatic secondary battery, a porous elastic member, and other members, and FIG. 8(B) is a view corresponding to FIG. 8 according to a fourth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, several preferred embodiments of the battery pack disclosed herein will be described with reference to the drawings as appropriate. Matters necessary for implementing the present invention other than those specifically mentioned in this specification (for example, the general configuration and manufacturing process of a prismatic secondary battery that do not characterize the present invention) can be understood as design matters for those skilled in the art based on prior art in the relevant field. The battery pack disclosed herein can be implemented based on the contents disclosed in this specification and common technical knowledge in the relevant field.

[0013] In the following drawings, the same reference numerals are used to designate components and parts that perform the same function, and redundant explanations may be omitted or simplified. In addition, in this specification, the expression "A to B" indicating a range means not less than A and not more than B, and also encompasses the meanings of "preferably larger than A" and "preferably smaller than B."

[0014] 1 is a perspective view schematically illustrating a battery pack 500 according to one embodiment. The battery pack 500 includes a plurality of prismatic secondary batteries 100, a plurality of porous elastic members 200, and a restraining mechanism 300. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z in the drawings represent the short side direction, the long side direction perpendicular to the short side direction, and the up-down direction of the prismatic secondary battery 100, respectively. The short side direction X is also the arrangement direction of the prismatic secondary batteries 100. However, these directions are merely used for convenience of explanation and do not limit the installation form of the battery pack 500 in any way.

[0015] The restraining mechanism 300 is configured to apply a specified restraining pressure to the multiple prismatic secondary batteries 100 and the multiple porous elastic members 200 in the arrangement direction X. Here, the restraining mechanism 300 is composed of a pair of end plates 310, a pair of side plates 320, and multiple screws 330. The pair of end plates 310 are aligned in the predetermined arrangement direction X. The pair of end plates 310 are arranged at both ends of the battery pack 500 in the arrangement direction X. The multiple prismatic secondary batteries 100 are arranged between the pair of end plates 310 along the arrangement direction X. The multiple porous elastic members 200 are each arranged between adjacent prismatic secondary batteries 100 in the arrangement direction X. The pair of end plates 310 sandwich the multiple prismatic secondary batteries 100 and the multiple porous elastic members 200 in the arrangement direction X.

[0016] The pair of side plates 320 bridge the pair of end plates 310. The pair of side plates 320 are fixed to the end plates 310 with a plurality of screws 330 so that the restraining load is, for example, approximately 10 to 15 kN. This applies a restraining load to the plurality of prismatic secondary batteries 100 and the plurality of porous elastic members 200 in the arrangement direction X, holding the battery pack 500 together. However, the restraining mechanism is not limited to this. The restraining mechanism 300 may include, for example, a plurality of restraining bands or bind bars instead of the side plates 320.

[0017] The prismatic secondary battery 100 is a battery that can be repeatedly charged and discharged. In this specification, the term "secondary battery" refers to any power storage device that can be repeatedly charged and discharged, and is a concept that encompasses so-called storage batteries (chemical batteries) such as lithium-ion secondary batteries and nickel-metal hydride batteries, and capacitors (physical batteries) such as lithium-ion capacitors and electric double-layer capacitors. Furthermore, the shape, size, number, arrangement, connection method, etc. of the prismatic secondary batteries 100 that make up the battery pack 500 are not limited to the embodiments disclosed herein and can be modified as appropriate.

[0018] FIG. 2 is a perspective view of a prismatic secondary battery 100. As shown in FIGS. 1 and 2, a plurality of prismatic secondary batteries 100 are arranged in an arrangement direction X via a porous elastic member 200 so that long side walls 12b (described later) face each other. FIG. 3 is a schematic longitudinal cross-sectional view taken along line III-III in FIG. 2. As shown in FIG. 3, the prismatic secondary battery 100 includes a battery case 10, an electrode assembly 20, a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collector 50, a negative electrode current collector 60, and a nonaqueous electrolyte (not shown). The prismatic secondary battery 100 here is a lithium-ion secondary battery.

[0019] The battery case 10 is a housing that houses the electrode assembly 20 and the nonaqueous electrolyte. As shown in FIG. 1, the battery case 10 has a flat, bottomed, rectangular parallelepiped (rectangular) outer shape. The material of the battery case 10 may be the same as that conventionally used, and is not particularly limited. The battery case 10 is preferably made of a metal, and more preferably made of, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like. As shown in FIG. 2, the battery case 10 includes an exterior body 12 having an opening 12h and a sealing plate (lid) 14 that seals the opening 12h. As in this embodiment, the battery case 10 preferably includes an exterior body 12 having an opening 12h and a sealing plate 14 that seals the opening 12h.

[0020] As shown in FIG. 2, the exterior body 12 includes a bottom wall 12a, a pair of long side walls 12b extending from the bottom wall 12a and facing each other, and a pair of short side walls 12c extending from the bottom wall 12a and facing each other. The bottom wall 12a is substantially rectangular. The bottom wall 12a faces the opening 12h. The long side walls 12b are flat. As can be seen from FIG. 1, the long side walls 12b are the surfaces facing the porous elastic member 200 (see also FIGS. 7 and 8). Here, the long side walls 12b are in direct contact with the porous elastic member 200. The long side walls 12b and the short side walls 12c are examples of the first and second side walls disclosed herein.

[0021] In a plan view, the area of ​​the long side wall 12b is larger than the area of ​​the short side wall 12c. Although not particularly limited, in the case of a high-capacity type used in a vehicle, the area of ​​the long side wall 12b is approximately 10,000 mm 2 It is better to have more than 15,000 mm 2 More than 20,000 mm is preferable. 2 More than 25,000 mm is more preferable. 2 More preferably, 30,000 mm 2 The above is particularly preferable. When the area of ​​the long side wall 12b is large in this way, it is particularly difficult for air to circulate through the interior of the porous elastic member 200, which will be described later, particularly in the central portion in the long side direction Y. Therefore, it is particularly effective to apply the technology disclosed herein. Furthermore, from the viewpoint of achieving the effects of the technology disclosed herein at a high level, the area of ​​the long side wall 12b is set to approximately 150,000 mm 2 The following is preferred:

[0022] The long side walls 12b are preferably horizontally long. That is, the length in the long side direction Y is preferably longer than the length in the up-down direction Z. The length of the long side walls 12b in the long side direction Y is preferably 200 mm or more, and the length in the up-down direction Z is preferably 100 mm or more. The application of the technology disclosed herein is particularly effective when the distance from the center to the edge is long. The ratio of the length in the long side direction Y to the length in the up-down direction Z of the long side walls 12b (length / width ratio) is preferably 1 / 1 to 2 / 3, more preferably 2 / 3 to 1 / 3, and even more preferably 1 / 3 to 1 / 15.

[0023] The sealing plate 14 is attached to the exterior body 12 so as to close the opening 12h of the exterior body 12. The sealing plate 14 faces the bottom wall 12a of the exterior body 12. The sealing plate 14 has a substantially rectangular shape in a plan view. The battery case 10 is integrated by joining (preferably welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The battery case 10 is hermetically sealed (sealed).

[0024] As shown in FIG. 3 , the sealing plate 14 is provided with a liquid inlet 15, a drain valve 17, and two terminal outlet holes 18 and 19. The liquid inlet 15 is for injecting nonaqueous electrolyte after the sealing plate 14 is assembled to the exterior body 12. The liquid inlet 15 is sealed with a sealing member 16. The drain valve 17 is configured to break when the pressure inside the battery case 10 reaches or exceeds a predetermined value, thereby discharging gas inside the battery case 10 to the outside. The terminal outlet holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z. The terminal outlet holes 18 and 19 each have an inner diameter large enough to insert the positive electrode terminal 30 and the negative electrode terminal 40 before they are attached to the sealing plate 14 (before crimping).

[0025] The non-aqueous electrolyte may be the same as conventional ones and is not particularly limited. The non-aqueous electrolyte contains a non-aqueous solvent and a supporting salt (electrolyte salt). The non-aqueous electrolyte may further contain additives as necessary. The non-aqueous solvent contains, for example, carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The non-aqueous solvent preferably contains carbonates. In particular, it is preferable that the non-aqueous solvent contains a cyclic carbonate and a chain carbonate. The supporting salt is, for example, a fluorine-containing lithium salt such as lithium hexafluorophosphate (LiPF6).

[0026] The positive electrode terminal 30 is disposed at one end of the sealing plate 14 in the long side direction Y (the left end in FIGS. 2 and 3). The negative electrode terminal 40 is disposed at the other end of the sealing plate 14 in the long side direction Y (the right end in FIGS. 2 and 3). As shown in FIG. 3, the positive electrode terminal 30 and the negative electrode terminal 40 extend from the inside to the outside of the sealing plate 14 through the terminal lead-out holes 18 and 19. The positive electrode terminal 30 and the negative electrode terminal 40 are fixed to the sealing plate 14. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are crimped to the peripheral portion surrounding the terminal lead-out holes 18 and 19 of the sealing plate 14 by crimping. Crimped portions 30c and 40c are formed at the ends of the positive electrode terminal 30 and the negative electrode terminal 40 on the exterior body 12 side (the lower end in FIG. 3).

[0027] As shown in Fig. 3, the positive electrode terminal 30 is electrically connected to the positive electrode 22 (see Fig. 6) of the electrode assembly 20 via a positive electrode current collector 50 inside the exterior housing 12. The negative electrode terminal 40 is electrically connected to the negative electrode 24 (see Fig. 6) of the electrode assembly 20 via a negative electrode current collector 60 inside the exterior housing 12. The positive electrode terminal 30 is insulated from the sealing plate 14 by an internal insulating member 80 and a gasket 90. The negative electrode terminal 40 is insulated from the sealing plate 14 by the internal insulating member 80 and a gasket 90.

[0028] A plate-shaped positive electrode external conductive member 32 and a plate-shaped negative electrode external conductive member 42 are attached to the outer surface of the sealing plate 14. The positive electrode external conductive member 32 is electrically connected to the positive electrode terminal 30. The negative electrode external conductive member 42 is electrically connected to the negative electrode terminal 40. The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are members to which bus bars or the like are attached that electrically connect multiple prismatic secondary batteries 100 to each other. The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are insulated from the sealing plate 14 by an external insulating member 92. Although not shown in FIG. 1 , when the battery pack 500 is in use, adjacent prismatic secondary batteries 100 are electrically connected to each other. For example, of adjacent prismatic secondary batteries 100, the positive electrode external conductive member 32 of one prismatic secondary battery 100 and the negative electrode external conductive member 42 of the other prismatic secondary battery 100 are electrically connected by a bus bar or the like. As a result, the battery packs 500 are electrically connected in series.

[0029] FIG. 4 is a perspective view schematically showing an electrode assembly 20 attached to a sealing plate 14. The electrode assembly 20 has a plurality of electrode assemblies. The configuration of the electrode assemblies may be the same as conventional ones and is not particularly limited. Here, the electrode assembly 20 has three electrode assemblies 20a, 20b, and 20c. However, the number of electrode assemblies arranged inside one exterior housing 12 is not particularly limited and may be two or four or more. Here, the electrode assemblies 20a, 20b, and 20c are electrically connected in parallel. The electrode assemblies 20a, 20b, and 20c are arranged side by side in the short side direction X. The electrode assemblies 20a, 20b, and 20c each have a flattened outer shape. Here, the electrode assemblies 20a, 20b, and 20c are each wound electrode assemblies. The electrode bodies 20a, 20b, and 20c are disposed inside the exterior body 12 with their respective winding axes WL (see FIG. 6) oriented substantially parallel to the long side direction Y. The end face of the electrode body 20a that is perpendicular to the winding axis WL (in other words, the stacking surface where the positive electrode 22 and the negative electrode 24 are stacked) faces the short side wall 12c.

[0030] FIG. 5 is a perspective view schematically illustrating the electrode body 20b. Note that, although the electrode body 20b will be described in detail below as an example, the electrode bodies 20a and 20c can also have a similar configuration. The electrode body 20b has a pair of curved portions (R portions) 20r and a flat portion 20f connecting the pair of curved portions 20r. One curved portion 20r (upper side of FIG. 5) faces the sealing plate 14, and the other curved portion 20r (lower side of FIG. 5) faces the bottom wall 12a of the exterior body 12. The flat portion 20f faces the long side wall 12b of the exterior body 12. The flat portions 20f of the electrode bodies 20a, 20b, and 20c adjacent to each other in the short side direction X face each other.

[0031] 6 is a schematic diagram showing the configuration of the electrode assembly 20b. The electrode assembly 20b has a positive electrode 22, a negative electrode 24, and a separator 26. In this example, the electrode assembly 20b is configured by stacking a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 with a strip-shaped separator 26 interposed between them and winding them around a winding axis WL. The direction of the winding axis WL is approximately parallel to the long side direction Y. However, in other embodiments, the electrode assembly 20b may be a stacked electrode assembly formed by stacking multiple square-shaped (typically rectangular) positive electrodes and multiple square-shaped (typically rectangular) negative electrodes in an insulated state.

[0032] The positive electrode 22 may be the same as a conventional positive electrode 22 and is not particularly limited. As shown in FIG. 6, the positive electrode 22 has a positive electrode core 22c, a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed to at least one surface of the positive electrode core 22c. However, the positive electrode protective layer 22p is not essential and can be omitted in other embodiments. The positive electrode core 22c is strip-shaped. The positive electrode core 22c is preferably made of metal, and more preferably made of metal foil. In this example, the positive electrode core 22c is aluminum foil.

[0033] A plurality of positive electrode tabs 22t are provided at one end of the positive electrode core 22c in the long side direction Y (the left end in FIG. 6). The plurality of positive electrode tabs 22t protrude toward one side in the long side direction Y (the left side in FIG. 6). The plurality of positive electrode tabs 22t protrude further in the long side direction Y than the separator 26. Here, the positive electrode tab 22t is part of the positive electrode core 22c and is made of metal foil (aluminum foil). As shown in FIGS. 3 to 6, the plurality of positive electrode tabs 22t are stacked at one end in the long side direction Y (the left end in FIGS. 3 to 6) to form a positive electrode tab group 23. The positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via a positive electrode current collector 50.

[0034] As shown in Fig. 6, the positive electrode active material layer 22a is provided in a strip shape along the longitudinal direction of the positive electrode substrate 22c. The positive electrode active material layer 22a contains a positive electrode active material that can reversibly store and release charge carriers. Examples of the positive electrode active material include lithium transition metal composite oxides. The positive electrode active material layer 22a may contain optional components other than the positive electrode active material, such as various additive components such as a binder and a conductive material.

[0035] As shown in Fig. 6, the positive electrode protective layer 22p is provided at the boundary between the positive electrode core 22c and the positive electrode active material layer 22a in the long side direction Y. The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a. The positive electrode protective layer 22p contains an inorganic filler (e.g., alumina). The positive electrode protective layer 22p may contain optional components other than the inorganic filler, such as a conductive material, a binder, and various additive components.

[0036] The negative electrode 24 may be the same as a conventional negative electrode 24 and is not particularly limited. As shown in FIG. 6, the negative electrode 24 has a negative electrode core 24c and a negative electrode active material layer 24a fixed to at least one surface of the negative electrode core 24c. The negative electrode core 24c is strip-shaped. The negative electrode core 24c is preferably made of metal, and more preferably made of metal foil. In this example, the negative electrode core 24c is copper foil.

[0037] A plurality of negative electrode tabs 24t are provided at one end of the negative electrode core 24c in the long side direction Y (the right end in FIG. 6). The plurality of negative electrode tabs 24t protrude toward one side in the long side direction Y (the right side in FIG. 6). The plurality of negative electrode tabs 24t protrude further in the long side direction Y than the separator 26. The plurality of negative electrode tabs 24t protrude further in the long side direction Y than the separator 26. Here, the negative electrode tab 24t is part of the negative electrode core 24c and is made of metal foil (copper foil). As shown in FIGS. 3 to 6, the plurality of negative electrode tabs 24t are stacked at one end in the long side direction Y (the right end in FIGS. 3 to 6) to form a negative electrode tab group 25. The negative electrode tab group 25 is provided at a position symmetrical to the positive electrode tab group 23 in the long side direction Y. The negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via a negative electrode current collector 60.

[0038] As shown in FIG. 6, the negative electrode active material layer 24a is provided in a strip shape along the longitudinal direction of the negative electrode substrate 24c. The length Ln of the negative electrode active material layer 24a in the long side direction Y is equal to or longer than the length La of the positive electrode active material layer 22a in the long side direction Y. The negative electrode active material layer 24a contains a negative electrode active material that can reversibly store and release charge carriers. Examples of the negative electrode active material include carbon materials such as graphite. The negative electrode active material layer 24a may contain optional components other than the negative electrode active material, such as various additive components such as a binder, a thickener, and a dispersant.

[0039] The separator 26 is disposed between the positive electrode 22 and the negative electrode 24. The separator 26 is a member that insulates the positive electrode 22 from the negative electrode 24. The length Ls of the separator 26 in the long side direction Y is equal to or longer than the length Ln of the negative electrode active material layer 24a in the long side direction Y. The separator 26 is preferably a porous sheet made of a resin such as a polyolefin resin, such as polyethylene (PE) or polypropylene (PP).

[0040] As shown in FIG. 3, the positive electrode current collecting part 50 forms a conductive path that electrically connects the positive electrode tab group 23, which is made up of multiple positive electrode tabs 22t, to the positive electrode terminal 30. The positive electrode current collecting part 50 includes a positive electrode first current collecting part 51 and a positive electrode second current collecting part 52. The positive electrode first current collecting part 51 is attached to the inner surface of the sealing plate 14. The positive electrode second current collecting part 52 extends along the short side wall 12c of the exterior body 12. As shown in FIGS. 3 to 5, the positive electrode second current collecting part 52 is attached to the electrode body 20b.

[0041] 3, the negative electrode current collecting part 60 forms a conductive path that electrically connects the negative electrode tab group 25 consisting of the multiple negative electrode tabs 24t to the negative electrode terminal 40. The negative electrode current collecting part 60 includes a negative electrode first current collecting part 61 and a negative electrode second current collecting part 62. The configurations of the negative electrode first current collecting part 61 and the negative electrode second current collecting part 62 may be the same as those of the positive electrode first current collecting part 51 and the positive electrode second current collecting part 52 of the positive electrode current collecting part 50.

[0042] As described above, the porous elastic members 200 are disposed between the plurality of prismatic secondary batteries 100 in the arrangement direction X. That is, the prismatic secondary batteries 100 and the porous elastic members 200 are alternately arranged in the arrangement direction X. However, it is sufficient that the porous elastic members 200 are disposed between at least two prismatic secondary batteries 100 adjacent to each other in the arrangement direction X; they do not necessarily have to be disposed between all of the prismatic secondary batteries 100. The porous elastic members 200 are preferably disposed between 50% or more, and more preferably 80% or more of the prismatic secondary batteries 100. The porous elastic members 200 may be separate from the prismatic secondary batteries 100, or may be fixed to and integrated with the prismatic secondary batteries 100. The porous elastic members 200 may be sandwiched between two opposing prismatic secondary batteries 100, or may be adhered to the prismatic secondary batteries 100 with adhesive, tape, or the like. Here, the porous elastic member 200 is in direct contact with the long side wall 12b of the prismatic secondary battery 100. However, as will be described in the modified example below, other members may be interposed between the prismatic secondary battery 100 and the porous elastic member 200.

[0043] The porous elastic member 200 is configured to be elastically deformable at least in the arrangement direction X. Although not particularly limited, the elastic force of the porous elastic member 200 is generally 1 kN / mm to 10 ×3 The porous elastic member 200 preferably has a strength of kN / mm. The porous elastic member 200 is a porous structure having a plurality of communicating pores that communicate with the outside. The porous elastic member 200 may have a three-dimensional mesh structure having communicating pores that are three-dimensionally interconnected. The porosity of the porous elastic member 200 (pore volume / volume of the porous elastic member 200) is preferably 10 to 90 volume %, more preferably 20 to 80 volume %, and even more preferably 25 to 75 volume %. This allows the effects of the technology disclosed herein to be exerted at a high level. The porous elastic member 200 is preferably made of a resin material. Examples of resin materials include natural rubber, synthetic rubber, silicone resin, and urethane resin.

[0044] When the prismatic secondary battery 100 expands during charging or other such events, the load applied to the porous elastic member 200 increases. This causes air to escape (be exhausted) from the porous elastic member 200, compressing the porous elastic member 200. This prevents the prismatic secondary battery 100 from being subjected to an excessively large restraining load. On the other hand, when the prismatic secondary battery 100 contracts during discharging or other such events, the load applied to the porous elastic member 200 decreases. This causes the porous elastic member 200 to absorb air from the outside, expand, and then return to its original shape. This allows the prismatic secondary battery 100 to be stably pressed with a restraining load greater than or equal to a predetermined value.

[0045] The shape, size, and arrangement of the porous elastic member 200 can be determined appropriately depending on, for example, the shape, size, and capacity (degree of expansion and contraction) of the prismatic secondary battery 100. The thickness of the porous elastic member 200 is preferably 1 to 10 mm, more preferably 1 to 8 mm, and even more preferably 3 to 5 mm, before being assembled into the battery pack 500 and compressed. The thickness of the porous elastic member 200 (length in the arrangement direction X) is preferably 2 to 9 mm, more preferably 3 to 8 mm, and even more preferably 4 to 7 mm, before being assembled into the battery pack 500 and compressed.

[0046] FIG. 7 is a plan view schematically illustrating the positional relationship between a prismatic secondary battery 100 and a porous elastic member 200. In FIG. 7, the prismatic secondary battery 100 is shown in a simplified manner, with reference numerals omitted for components other than the positive terminal 30, the negative terminal 40, and the long side wall 12b. As shown in FIG. 7, the porous elastic member 200 includes a first portion 210 and a second portion 220. The first portion 210 and the second portion 220 are spaced apart in the long side direction Y, which is perpendicular to the arrangement direction X. The first portion 210 and the second portion 220 have the same shape. Specifically, they are substantially rectangular. However, they may have other shapes (e.g., substantially circular or elliptical). The porous elastic member 200 has line symmetry with respect to a center line CL in one direction (here, the long side direction Y) of the long side wall 12b of the prismatic secondary battery 100. The overall length L1 of the porous elastic member 200 in the long side direction Y is preferably approximately the same (approximately ±1 cm) as the length (average length) La of the positive electrode active material layer 22a in the long side direction Y (see FIG. 6). The overall length L1 may be shorter than the length Ls of the separator 26 in the long side direction Y.

[0047] A gap 250 is provided between the first portion 210 and the second portion 220 in the long side direction Y. In FIG. 7, the outer peripheral edge OE of the porous elastic member 200 when assembled into the battery pack 500, i.e., the outermost portion visible from the outside in the battery pack 500, is indicated by a dashed line. The gap 250 is an example of a gas flow path extending inward from the outer peripheral edge OE of the porous elastic member 200. In this embodiment, the gap 250 extends linearly (e.g., straight) along the vertical direction Z in a plan view. The gap 250 is formed so as to penetrate the porous elastic member 200 from the upper side U to the lower side D. In other words, both ends of the gap 250 in the vertical direction Z are open. The gap 250 is formed so as to include the center C of the long side wall 12b of the prismatic secondary battery 100. The gap 250 is formed so as to include the center portion of the long side direction Y of the prismatic secondary battery 100 (particularly the center line CL). The center portion of the long side wall 12b experiences a large change in thickness during charge and discharge. Furthermore, air is particularly unlikely to circulate through the portion of the porous elastic member 200 facing the center portion of the long side wall 12b. For this reason, by including the center C of the long side wall 12b and / or the center portion in the long side direction Y in the gap 250, the effects of the technology disclosed herein can be exerted to a high level.

[0048] The area of ​​the porous elastic member 200 in plan view is 10,000 mm 2 More than 15,000mm is preferable. 2 More than 25,000mm is more preferable. 2 The above is even more preferable. The ratio of the area of ​​the porous elastic member 200 to the area of ​​the long side wall 12b is preferably approximately 50% or more, more preferably 60% or more, even more preferably 70% or more, even more preferably 75% or more, and particularly preferably 80% or more. In such cases, it is difficult for air to circulate throughout the porous elastic member 200, and therefore applying the technology disclosed herein is particularly effective. Furthermore, from the viewpoint of achieving the effects of the technology disclosed herein at a high level, the above area ratio is preferably approximately 95% or less, more preferably 90% or less, and more preferably 85% or less.

[0049] In this specification, the "area of ​​the porous elastic member 200 in a plan view" refers to the area in contact with the opposing member (here, the long side wall 12b), and if the porous elastic member 200 is composed of multiple parts, it refers to the total area of ​​those parts. For example, in FIG. 7, it is the total area of ​​the first part 210 and the second part 220. Furthermore, if the porous elastic member 200 has slits, recesses, or other parts that do not come into contact with the opposing member, as will be described later in a modified example, the area refers to the area excluding the areas of the slits, recesses, etc.

[0050] FIG. 8 is a partially enlarged top view of a key portion of the battery pack 500, showing a prismatic secondary battery 100 and a porous elastic member 200. As shown in FIG. 8, when the porous elastic member 200 is assembled into the battery pack 500, it has a gap 250 between the first portion 210 and the second portion 220. The gap 250 serves as a gas flow path that communicates with the outside air. Therefore, even when the porous elastic member 200 is assembled into the battery pack 500, air can be easily drawn in through the gap 250. Therefore, when the prismatic secondary battery 100 contracts, the porous elastic member 200 can be stably restored to its original shape, preventing an unintended decrease in the restraining load of the battery pack 500.

[0051] The battery pack 500 can be used for various purposes, but can be suitably used, for example, as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car, a truck, etc. The type of vehicle is not particularly limited, but examples include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and a battery electric vehicle (BEV).

[0052] Although the preferred embodiment of the present invention has been described above, the above embodiment is merely an example. The present invention can be implemented in various other forms. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. The technology described in the claims includes various modifications and alterations of the above-exemplified embodiment. For example, it is possible to replace part of the above-described embodiment with other modifications, or to add other modifications to the above-described embodiment. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate.

[0053] For example, in the above-described embodiment, as shown in Fig. 7, the porous elastic member 200 is composed of two parts, i.e., a first part 210 and a second part 220 that are spaced apart in the long side direction Y, and the gap 250 between the first part 210 and the second part 220 forms the gas flow path. However, the porous elastic member 200 may be composed of three or more parts. Furthermore, the first part 210 and the second part 220 may be spaced apart in the up-down direction Z instead of in the long side direction Y.

[0054] <First Modification> FIG. 9 is a diagram corresponding to FIG. 7 and related to the first modified example. In this modified example, the porous elastic member 200a may be similar to the porous elastic member 200 described above, except that it is composed of four portions: a first portion 210a and a second portion 220a spaced apart in the long side direction Y on the upper side in the vertical direction Z; and a third portion 230a and a fourth portion 240a spaced apart in the long side direction Y on the lower side in the vertical direction Z. The porous elastic member 200a is symmetrical in the long side direction Y and the vertical direction Z with respect to a center line CL indicated by a dashed line. The porous elastic member 200a has cross-shaped gaps 250a between the four portions. The gaps 250a are formed to include the centers C of the long side walls 12b of the prismatic secondary battery 100. The gaps 250a are formed to include the central portions (particularly the center line CL) of the prismatic secondary battery 100 in the long side direction Y and the vertical direction Z. The gap 250a constitutes a gas flow path that extends inward from the outer periphery OE of the porous elastic member 200a.

[0055] <Second Modification> FIG. 10 is a view corresponding to FIG. 7 and related to a second modified example. In this modified example, the porous elastic member 200b includes, in addition to a first portion 210b and a second portion 220b, a connecting portion 230b connecting the first portion 210b and the second portion 220b at the center in the long-side direction Y, and may be similar to the porous elastic member 200 described above, except that the porous elastic member 200b is integrally formed. The porous elastic member 200b has line symmetry in the long-side direction Y. The porous elastic member 200b has two slits 250b and 260b between the first portion 210b and the second portion 220b in the long-side direction Y. One of the slits 250b extends inward from the upper side of the outer circumferential edge OE. In other words, it opens upward. The other slit 260b extends inward from the lower side of the outer circumferential edge OE. In other words, it opens downward. The slits 250b and 260b are an example of a gas flow path that extends inward from the outer periphery OE of the porous elastic member 200b.

[0056] <Third Modification> FIG. 11(A) is a view corresponding to FIG. 7 and related to a third modified example. In this modified example, the porous elastic member 200c is composed of a first portion 210c and a second portion 220c arranged on the left and right sides in the long-side direction Y, and a single recess (thin-walled portion) 250c connecting the first portion 210c and the second portion 220c. The porous elastic member 200c may be similar to the porous elastic member 200 described above, except that the first portion 210c and the second portion 220c are integrally formed. Like the gap 250, the recess 250c extends linearly (e.g., straight) along the vertical direction Z in a plan view and is formed to include the center C of the long side wall 12b of the prismatic secondary battery 100. The recess 250c is formed to include the center portion (particularly the center line CL) in the long-side direction Y of the prismatic secondary battery 100. However, the porous elastic member 200c may have two or more recesses. In this case, the recesses may be aligned in a predetermined direction (e.g., the long-side direction Y) or may be arranged in a striped pattern. Furthermore, the recesses may be arranged so as to intersect in two or more predetermined directions (for example, the long side direction Y and the vertical direction Z).

[0057] 11(B) is a cross-sectional view taken along line (b)-(b) in (A). As shown in FIG. 11(B), the first portion 210c and the second portion 220c have approximately the same thickness. The recess 250c is a portion thinner than the first portion 210c and the second portion 220c. The recess 250c is an example of a gas flow path extending inward from the outer peripheral edge OE of the porous elastic member 200c.

[0058] Furthermore, for example, in the above-described embodiment, the porous elastic member 200 was disposed between adjacent prismatic secondary batteries 100 in the arrangement direction X, and both the front and back surfaces (both surfaces in the arrangement direction X) of the porous elastic member 200 abutted against the long side walls 12b of the prismatic secondary batteries 100. However, other members may be interposed between the prismatic secondary batteries 100 and the porous elastic member 200. Examples of other members that may be interposed between the prismatic secondary batteries 100 and the porous elastic member 200 include, for example, a non-porous insulating film; a heat-resistant member containing a high-melting-point resin; a heat-resistant member containing a resin material and ceramic particles; and a heat-insulating member containing silica aerogel or a nanoporous material mainly composed of silica. The shape, size, and arrangement of the other members can be determined appropriately depending on, for example, the shape, size, and position of the gas flow path of the porous elastic member 200. The other members may be, for example, sheet-shaped or may have the same shape as the porous elastic member 200.

[0059] <Fourth Modification> FIG. 12(A) is a plan view schematically showing the positional relationship between the prismatic secondary battery 100, the porous elastic member 200d, and the other member 400. FIG. 12(B) is a view corresponding to FIG. 8 for a fourth modified example. As shown in FIG. 12(B), in this modified example, the other member 400 abuts against the porous elastic member 200d, and a gas flow path is provided on the surface of the other member 400 that contacts the porous elastic member. That is, as shown in FIG. 12(A), in this modified example, the porous elastic member 200d is sheet-shaped and has a uniform thickness. The porous elastic member 200d may be similar to the porous elastic member 200 described above, except that it has a rectangular shape that is slightly smaller than the long side wall 12b of the prismatic secondary battery 100.

[0060] The other component 400 includes a first portion 410 and a second portion 420 spaced apart from each other in the long-side direction Y. The first portion 410 and the second portion 420 are spaced apart from each other in the long-side direction Y, which is perpendicular to the arrangement direction X. The first portion 410 and the second portion 420 are rectangular and smaller than the porous elastic member 200d, and are shorter in the vertical direction Z than the porous elastic member 200d. A gap 450 is formed between the first portion 410 and the second portion 420 in the long-side direction Y. The outer periphery OE of the other component 400 when assembled into the battery pack 500, i.e., the portion exposed to the outside, is indicated by a dashed line. The gap 450 is an example of a gas flow path extending inward from the outer periphery OE of the other component 400.

[0061] As shown in FIG. 12(B), in this modification, a porous elastic member 200d is disposed between adjacent prismatic secondary batteries 100 in the arrangement direction X, and another member 400 is disposed between the prismatic secondary batteries 100 and the porous elastic member 200d. Therefore, one surface of the porous elastic member 200d in the arrangement direction X abuts against the prismatic secondary battery 100, and the other surface abuts against the other member 400. When assembled into the battery pack 500, the other member 400 has a gap 450 between the first portion 410 and the second portion 420. The gap 450 serves as a gas flow path communicating with the outside air. Therefore, even when the porous elastic member 200d is assembled into the battery pack 500, the porous elastic member 200d can easily draw in air through the gap 450. Therefore, similar to the case where a gas flow path is provided in the porous elastic member 200 itself, the porous elastic member 200 can be stably restored to its original shape when the rectangular secondary battery 100 contracts, and an unintended decrease in the restraint load of the battery pack 500 can be prevented.

[0062] Furthermore, in the fourth modified example described above, the gap 450 of the other component 400 constitutes a gas flow path communicating with the outside air. However, the other component 400 may have a recess on at least the surface that contacts the porous elastic member 200d, instead of the gap 450, as in the third modified example described above. In this case, the recess may be provided only on the surface that contacts the porous elastic member 200d, or on both surfaces. Furthermore, in the fourth modified example described above, one porous elastic member 200d is disposed between adjacent prismatic secondary batteries 100. However, two or more porous elastic members 200d may be disposed between adjacent prismatic secondary batteries 100. For example, the other component 400 sandwiched between a pair of porous elastic members 200d may be disposed between adjacent prismatic secondary batteries 100, and both the front and back surfaces (both surfaces in the arrangement direction X) of the other component 400 may abut against the porous elastic member 200d.

[0063] As described above, specific aspects of the technology disclosed herein include those described in the following sections. Item 1: A battery pack comprising a plurality of prismatic secondary batteries arranged along a predetermined arrangement direction, a porous elastic member arranged between adjacent prismatic secondary batteries in the arrangement direction, and a restraint mechanism that applies a restraint load to the plurality of prismatic secondary batteries and the porous elastic member from the arrangement direction, wherein the porous elastic member has a plurality of communication holes that communicate with the outside and is configured to be elastically deformable in the arrangement direction by taking in or exhausting gas, and the battery pack satisfies at least one of the following configurations (1) and (2): (1) the porous elastic member has a gas flow path that extends inward from its outer periphery when assembled in the battery pack; (2) another member is further provided between the prismatic secondary batteries and the porous elastic member, and the another member has a gas flow path that extends inward from its outer periphery on at least the surface that comes into contact with the porous elastic member when assembled in the battery pack. Item 2: The battery pack according to item 1, wherein the porous elastic member and / or the other member includes a first portion and a second portion spaced apart in at least one direction perpendicular to the arrangement direction, and the gap between the first portion and the second portion forms the gas flow path. Item 3: The battery pack according to item 1 or 2, wherein the porous elastic member has a slit extending inward from an outer periphery thereof when assembled into the battery pack, and the slit forms the gas flow path. Item 4: The battery pack according to any one of Items 1 to 3, wherein the porous elastic member and / or the other member has a recess extending inward from an outer periphery when assembled into the battery pack, and the recess forms the gas flow path. Item 5: The prismatic secondary battery includes a battery case and an electrode assembly housed in the battery case. The battery case is formed by joining an exterior body having a bottom wall, a pair of first side walls extending from the bottom wall and facing each other, a pair of second side walls extending from the bottom wall and facing each other, and an opening facing the bottom wall, and a sealing plate that seals the opening of the exterior body. The first side wall faces the porous elastic member, and the area of ​​the first side wall is 20,000 mm2 in plan view. 2 Item 5. The battery pack according to any one of items 1 to 4, wherein: Item 6: The battery pack according to item 5, wherein the ratio of the area of ​​the porous elastic member to the area of ​​the first side wall in plan view is 50% or more. Item 7: The battery pack according to any one of items 1 to 6, wherein the porous elastic member has a porosity of 10 to 90% by volume. Item 8: The battery pack according to any one of items 1 to 7, wherein the porous elastic member is made of resin. [Explanation of symbols]

[0064] OE outer rim 10 Battery case 12 Exterior body 14 Sealing plate 20 Electrode group 20a, 20b, 20c electrode body 100 Prismatic secondary battery 200, 200a, 200b, 200c, 200d Porous elastic member 250, 250a Gap (gas flow path) 250b, 260b Slits (gas flow path) 250c Recess (gas flow path) 300 Restraint mechanism 400 Other parts 450 Gap (gas flow path) 500 battery packs

Claims

1. a plurality of prismatic secondary batteries arranged along a predetermined arrangement direction; a porous elastic member disposed between adjacent prismatic secondary batteries in the arrangement direction; a restraining mechanism that applies a restraining load to the plurality of prismatic secondary batteries and the porous elastic member in the arrangement direction; A battery pack comprising: The porous elastic member is made of resin, has a plurality of communication holes communicating with the outside, and is configured to be elastically deformable in the arrangement direction by taking in or discharging gas, and The following configurations (1) and (2): (1) When the porous elastic member is assembled to the battery pack, the porous elastic member has a gas flow path that extends inward from an outer circumferential edge and is connected to the communication hole; (2) Another member is further provided between the prismatic secondary battery and the porous elastic member, and the another member has, on at least a surface that contacts the porous elastic member when assembled into the battery pack, a gas flow path that extends inward from an outer periphery and connects to the communication hole of the porous elastic member; At least one of the following is satisfied: Each of the plurality of prismatic secondary batteries has a battery case including a pair of first side walls, the porous elastic member is disposed between the first side walls of the prismatic secondary batteries adjacent to each other in the arrangement direction, The area of ​​the first side wall is 15,000 mm in plan view. ２ That's all, a ratio of an area of ​​the porous elastic member to an area of ​​the first side wall in a plan view is 50% or more.

2. The area of ​​the first side wall is 25,000 mm 2 or more in a plan view. The battery pack according to claim 1 .

3. the porous elastic member and / or the other member includes a first portion and a second portion that are spaced apart from each other in at least one direction perpendicular to the arrangement direction, A gap between the first portion and the second portion constitutes the gas flow path. The battery pack according to claim 1 or 2.

4. the porous elastic member has a slit extending inward from an outer peripheral edge when assembled to the battery pack, and no porous elastic member is present in the entire thickness direction; The slit constitutes the gas flow path. The battery pack according to any one of claims 1 to 3.

5. the porous elastic member and / or the other member has a recessed portion formed on a surface thereof by extending inward from an outer circumferential edge and making the thickness thereof thinner than the surrounding area when assembled into the battery pack, The recess constitutes the gas flow path. The battery pack according to any one of claims 1 to 4.

6. In a plan view, the ratio of the area of ​​the porous elastic member to the area of ​​the first side wall is 80% or more. The battery pack according to any one of claims 1 to 5.

7. another member is interposed between the prismatic secondary battery and at least one surface of the porous elastic member; The battery pack according to any one of claims 1 to 6.

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