battery pack

Abstract

To provide a battery pack equipped with a spacer which is excellent in heat resistance and is capable of absorbing swelling of a secondary battery.SOLUTION: A battery pack disclosed herein includes: a plurality of square secondary batteries arranged along a prescribed arrangement direction X; and a spacer 200 arranged between adjacent square secondary batteries in the arrangement direction X. The spacer 200 includes a first part 210 and a second part 220. The first part 210 has an elastic modulus of 1 MPa or more and 10 MPa or less, whereas the second part 220 includes a porous part 222. In the porous part 222, a material which satisfies the following conditions occupies 50 mass% or more of the whole: (1) categorization of heat resistance based on JIS K 6380 (year 2014) is E or more; and (2) the elastic modulus in the arrangement direction X is 0.02 MPa or more and 0.9 MPa or less.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Conventionally, battery packs formed by electrically connecting a plurality of secondary batteries (single cells) have been widely used in vehicle drive power sources to achieve high output. Related prior art documents include Patent Documents 1 and 2.

[0003] For example, Patent Document 1 discloses a battery pack including a plurality of secondary batteries arranged in a predetermined arrangement direction, spacers arranged between adjacent secondary batteries in the arrangement direction, and a heat conduction suppressing member arranged between the secondary batteries and the spacers to suppress heat conduction between the secondary batteries. Patent Document 1 describes that the heat conduction suppressing member includes a heat insulating material having a structure in which a porous material such as silica xerogel is carried between fibers of a fiber sheet made of nonwoven fabric or the like, so that the structure can be stably maintained even when pressed from the outside (for example, when tightened by a restraining mechanism). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6913872 [Patent Document 2] International Publication No. 2019 / 146438 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, secondary batteries installed in vehicles and the like have become increasingly high-capacity. According to the inventors' investigations, there is still room for improvement when applying the above-mentioned technology to battery packs equipped with high-capacity secondary batteries. Specifically, high-capacity secondary batteries tend to swell with increasing charge / discharge cycles due to the increased amount of active material in the battery case. In this case, as described in Patent Document 1, if a heat conduction suppressing member can stably maintain its structure (in other words, has a high elastic modulus), it is difficult to absorb the swelling of the secondary battery. As a result, there is a risk of swelling of the entire battery pack and performance degradation of the secondary battery. Furthermore, high-capacity secondary batteries tend to generate heat during charge / discharge and short-circuiting. Therefore, even if a secondary battery generates heat, it is necessary to highly suppress the heat transfer to adjacent secondary batteries.

[0006] The present invention has been made in view of the above circumstances, and its main object is to provide a battery pack including a spacer that has excellent heat resistance and can absorb swelling of secondary batteries. [Means for solving the problem]

[0007] The present invention discloses a battery pack including a plurality of prismatic secondary batteries arranged in a predetermined arrangement direction and a spacer arranged between adjacent prismatic secondary batteries in the arrangement direction. The spacer includes a first portion and a second portion stacked in the arrangement direction, the first portion having an elastic modulus of 1 MPa to 10 MPa, and the second portion including a porous portion, the porous portion being made up of a material that satisfies all of the following conditions: 1) a heat resistance classification of E or higher according to JIS K 6380 (2014); and (2) an elastic modulus of 0.02 MPa to 0.9 MPa, both inclusive. The elastic modulus is the value calculated as the slope of an approximation line in the range of compressibility from 1 to 20% from a compression load-compressibility curve (horizontal axis: compressibility, vertical axis: compressive load) created by compressing the battery in the arrangement direction at a compression rate of 12 kPa / min up to a compressive load of 3.9 MPa.

[0008] In the present invention, the spacer includes a first portion satisfying the above elastic modulus and a second portion having a porous portion, so that it can stably apply a load to the secondary battery even when the secondary battery expands and contracts during charge and discharge. Furthermore, since the second portion has a porous portion mainly made of a material that satisfies both the above heat resistance category and the above elastic modulus, the spacer can combine heat resistance and swelling / absorption properties. Specifically, compared to when the second portion does not have a porous portion or when the porous portion does not satisfy the above heat resistance category, heat transfer to adjacent secondary batteries can be relatively suppressed. Furthermore, because the first portion satisfying the above elastic modulus and the second portion having a porous portion can each absorb the swelling of the secondary battery, swelling / absorption properties can be relatively improved compared to when, for example, the second portion does not satisfy the above elastic modulus, and thus performance degradation of the secondary battery after charge / discharge cycles can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view schematically showing a battery pack according to one 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. [Figure 4] FIG. 4 is a perspective view schematically showing the spacer of FIG. [Figure 5] FIG. 5 is a schematic FS curve. [Figure 6] 6(A) and (B) are schematic diagrams of the first part according to the first embodiment, where FIG. 6(A) is a plan view of a surface perpendicular to the thickness direction, and FIG. 6(B) is a longitudinal cross-sectional view along line VIB-VIB in FIG. 6(A). [Figure 7] FIG. 7 is a table showing the heat resistance classifications. [Figure 8] 8(A) and (B) are schematic diagrams of the first part according to the second embodiment, where FIG. 8(A) is a plan view of a surface perpendicular to the thickness direction, and FIG. 8(B) is a longitudinal cross-sectional view along line VIIIB-VIIIB in FIG. 8(A). DETAILED DESCRIPTION OF THE INVENTION

[0010] 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 battery pack or 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.

[0011] 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."

[0012] First Embodiment FIG. 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 arranged along an arrangement direction X and a plurality of spacers 200 arranged between adjacent prismatic secondary batteries 100 in the arrangement direction X. The battery pack 500 further includes 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 thickness direction of the prismatic secondary battery 100, the long side direction perpendicular to the thickness direction, and the up-down direction perpendicular to the thickness direction and the long side direction, respectively. The thickness 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.

[0013] The restraining mechanism 300 is configured to apply a specified restraining pressure to the multiple prismatic secondary batteries 100 and the multiple spacers 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 arranged on both ends of the multiple 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 spacers 200 in the arrangement direction X. The pair of end plates 310 are preferably made of metal. However, a portion of the end plates 310 may be made of resin.

[0014] The pair of side plates 320 bridge the pair of end plates 310. The pair of side plates 320 are preferably made of metal. However, they may be partially made of resin. 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 spacers 200 in the arrangement direction X, holding the battery pack 500 together. However, the configuration of the restraining mechanism is not limited to this. The restraining mechanism 300 may include, for example, a plurality of restraining bands, bind bars, etc. instead of the side plates 320.

[0015] The multiple prismatic secondary batteries 100 are arranged between a pair of end plates 310 along the arrangement direction X (in other words, the thickness direction X of the prismatic secondary batteries 100). The multiple prismatic secondary batteries 100 are preferably restrained by a restraining mechanism 300. Although not shown in FIG. 1 , when the battery pack 500 is in use, the multiple prismatic secondary batteries 100 are electrically connected by conductive members such as bus bars. The connection method is not particularly limited, and may be, for example, series, parallel, or multi-series / multi-parallel.

[0016] The prismatic secondary battery 100 is a battery that can be repeatedly charged and discharged. In this specification, the term "secondary battery" refers to a general power storage device that can be repeatedly charged and discharged, and is a concept that encompasses so-called storage batteries such as lithium-ion secondary batteries and nickel-metal hydride batteries, as well as capacitors such as lithium-ion capacitors and electric double-layer capacitors. Furthermore, the shape, size, number, arrangement, 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.

[0017] FIG. 2 is a perspective view of a prismatic secondary battery 100. 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 collecting member 50, a negative electrode current collecting member 60, and a nonaqueous electrolyte (not shown). The nonaqueous electrolyte may be the same as a conventional one and is not particularly limited. In this example, the prismatic secondary battery 100 is a lithium-ion secondary battery.

[0018] The battery case 10 is a housing that houses the electrode assembly 20 and the non-aqueous electrolyte. As shown in FIG. 2, 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 metal, and more preferably made of, for example, aluminum, an aluminum alloy, iron, an iron alloy, or the like. The battery case 10 includes an exterior body 12 and a sealing plate (lid) 14. As in this embodiment, the battery case 10 preferably includes the exterior body 12 and the sealing plate 14.

[0019] As shown in FIG. 2, the exterior body 12 includes a substantially rectangular bottom wall 12a, a pair of long side walls 12b extending from the long sides of the bottom wall 12a and facing each other, a pair of short side walls 12c extending from the short sides of the bottom wall 12a and facing each other, and an opening 12h (see FIG. 3) facing the bottom wall 12a. The long side walls 12b are surfaces facing the spacer 200. The area of ​​the long side walls 12b is larger than the area of ​​the short side walls 12c. The sealing plate 14 is a plate-like member that seals the opening 12h of the exterior body 12. As shown in FIG. 3, the sealing plate 14 is attached to the exterior body 12 so as to close the opening 12h. The sealing plate 14 faces the bottom wall 12a of the exterior body 12. The sealing plate 14 is substantially rectangular. The battery case 10 is integrated by joining (preferably welding) a sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The battery case 10 is hermetically sealed (sealed).

[0020] In this specification, the term "approximately rectangular" refers not only to a perfect rectangular shape (rectangular shape), but also to shapes such as those in which the corners connecting the long and short sides of the rectangle are rounded, or those in which the corners have notches.

[0021] 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 sealing plate 14 is preferably provided with the liquid inlet 15 and the drain valve 17. 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).

[0022] 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). The positive electrode terminal 30 and the negative electrode terminal 40 are preferably attached to the sealing plate 14. 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 terminal lead-out holes 18 and 19. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are crimped to the peripheral portion of the sealing plate 14 surrounding the terminal lead-out holes 18 and 19 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).

[0023] As shown in Fig. 3, the positive electrode terminal 30 is electrically connected to the positive electrode current collecting portion 23 of the electrode assembly 20 via a positive electrode current collecting member 50 inside the exterior housing 12. The negative electrode terminal 40 is electrically connected to the negative electrode current collecting portion 25 of the electrode assembly 20 via a negative electrode current collecting member 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.

[0024] As shown in FIGS. 2 and 3 , 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 conductive members such as bus bars that electrically connect multiple prismatic secondary batteries 100 to each other are attached. 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. The battery pack 500 is connected in series, for example, by electrically connecting the positive electrode external conductive member 32 of one of adjacent prismatic secondary batteries 100 to the negative electrode external conductive member 42 of the other prismatic secondary battery 100 via a bus bar or the like.

[0025] The electrode assembly 20 has a positive electrode and a negative electrode. The configuration of the electrode assembly 20 may be the same as that of a conventional electrode assembly and is not particularly limited. Furthermore, the number of electrode assemblies 20 arranged inside one exterior housing 12 is not particularly limited and may be more than one. Here, the electrode assembly 20 is a flat wound electrode assembly formed by stacking a strip-shaped positive electrode and a strip-shaped negative electrode in an insulated state via a separator and winding the stack around a winding axis. However, in other embodiments, the electrode assembly 20 may be a stacked electrode assembly formed by stacking multiple rectangular positive electrodes and multiple rectangular negative electrodes in an insulated state.

[0026] As shown in FIG. 3, a positive electrode current collector 23 is provided at one end of the electrode body 20 in the winding axis direction (long side direction Y in FIG. 3). A negative electrode current collector 25 is provided at the other end. A positive electrode current collector 50 is attached to the positive electrode current collector 23. A negative electrode current collector 60 is attached to the negative electrode current collector 25. The positive electrode current collector 50 forms a conductive path that electrically connects the positive electrode terminal 30 and the positive electrode of the electrode body 20. The negative electrode current collector 60 forms a conductive path that electrically connects the negative electrode terminal 40 and the negative electrode of the electrode body 20.

[0027] Here, the spacers 200 are arranged between the multiple prismatic secondary batteries 100 in the arrangement direction X. That is, the prismatic secondary batteries 100 and the spacers 200 are arranged alternately in the arrangement direction X. However, it is sufficient that the spacers 200 are arranged between at least two prismatic secondary batteries 100 adjacent to each other in the arrangement direction X, and they do not necessarily have to be arranged between all of the prismatic secondary batteries 100. Here, a pair of surfaces of the spacers 200 that are perpendicular to the arrangement direction X (both surfaces in the arrangement direction X) abut (are in direct contact with) 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 spacers 200.

[0028] FIG. 4 is a perspective view schematically illustrating a spacer 200. As shown in FIG. 4, the spacer 200 includes a first portion 210 and a second portion 220. The first portion 210 and the second portion 220 in FIG. 4 each have a flat plate-like outer shape. The first portion 210 and the second portion 220 are stacked in the arrangement direction X. The spacer 200 has a two-layer structure consisting of one first portion 210 and one second portion 220. The first portion 210 has a pair of surfaces (YZ planes in FIG. 4) perpendicular to the thickness direction X, one of which faces (abuts) against the second portion 220 and the other of which faces (abuts) against the long side wall 12b of the battery case 10. Here, the second portion 220 has a pair of surfaces (YZ plane in FIG. 4) perpendicular to the thickness direction X, one of which faces (here, abuts) the first portion 210, and the other of which faces (here, abuts) the long side wall 12b of the battery case 10.

[0029] The first portion 210 and the second portion 220 are preferably integrated. In particular, they are preferably integrated by a binding member. This prevents misalignment of the first portion 210 and the second portion 220. Furthermore, the productivity and workability of the battery pack 500 can be improved. In this specification, the term "integration" encompasses detachable fastening or non-detachable adhesion using a binding member, as well as fitting (mechanical joining) or integral molding without using a binding member. The first portion 210 and the second portion 220 may be fixed with, for example, tape or the like as a binding member, or may be entirely wrapped and covered with a resin sheet or laminate film or the like as a binding member, or may be bonded by chemical or physical forces via an adhesive or adhesive layer (double-sided tape or the like) as a binding member, or may be processed as a single component by fitting or integral molding without using a binding member.

[0030] 4, the first portion 210 and the second portion 220 have approximately the same area in the YZ plane (processing errors are acceptable). The area in the YZ plane of each of the first portion 210 and the second portion 220 is preferably 50% or more, more preferably 70% or more, and particularly preferably 80% or more of the area of ​​the long side wall 12b (the surface facing the spacer 200) of the battery case 10. This allows the effects of the technology disclosed herein to be exerted to a high level.

[0031] 4, the thickness t1 of the first portion 210 is preferably 5% or more, for example, 5 to 15%, of the thickness (length in the thickness direction X) of the prismatic secondary battery 100 before it is assembled into the battery pack 500 and compressed. The thickness t2 of the second portion 220 is preferably 2% or more, for example, 2 to 20%, and more preferably 5% or more, for example, 5 to 15%, of the thickness (length in the thickness direction X) of the prismatic secondary battery 100 before it is assembled into the battery pack 500 and compressed. The sum of thickness t1 and thickness t2 is preferably 7% or more, for example, 7 to 35%, or even 10% or more, for example, 10 to 30%, of the thickness (length in the thickness direction X) of the prismatic secondary battery 100.

[0032] However, the shape, size, arrangement, etc. of the first portion 210 and the second portion 220 can be determined appropriately depending on, for example, the shape, size, capacity (degree of expansion / contraction), etc. of the prismatic secondary battery 100. The spacer 200 may have, for example, a three-layer structure (second portion 220 / first portion 210 / second portion 220) in which the second portion 220 is arranged on each of both side surfaces of the first portion 210 in the arrangement direction X, or conversely, a three-layer structure (first portion 210 / second portion 220 / first portion 210) in which the first portion 210 is arranged on each of both side surfaces of the second portion 220 in the arrangement direction X. The spacer 200 may have a structure of four or more layers, or may include portions other than the first portion 210 and the second portion 220.

[0033] The first portion 210 has an elastic modulus that satisfies a predetermined range, described below, and is configured to be elastically deformable in the arrangement direction X. Therefore, when the prismatic secondary battery 100 expands during charging or the like and the load applied to the first portion 210 increases, the first portion 210 is compressed. On the other hand, when the prismatic secondary battery 100 contracts during discharging or the like and the load applied to the first portion 210 decreases, the first portion 210 returns to its original shape. Therefore, by providing the first portion 210 to the spacer 200, even when the prismatic secondary battery 100 expands and contracts during charging and discharging, the prismatic secondary battery 100 can be stably pressed with a predetermined restraining load, and the load necessary to maintain performance can be stably applied. Furthermore, when the prismatic secondary battery 100 expands after a charge / discharge cycle, the first portion 210 can be suitably absorbed, and the expansion absorption of the spacer 200 can be further improved by a synergistic effect with the second portion 220, described below.

[0034] In this embodiment, the elastic modulus of the first portion 210 is 1 MPa to 10 MPa. The smaller the elastic modulus value, the softer the material is, and the easier it is to elastically deform in the thickness direction X (arrangement direction X). 1st part The elastic modulus of the first portion 210 is preferably 7 MPa or less, more preferably 5 MPa or less, and may be, for example, 3.3 MPa or less. By setting the elastic modulus of the first portion 210 to a predetermined value or less, the spacer 200 is more likely to be crushed when the prismatic secondary battery 100 is charged or when the prismatic secondary battery 100 swells. Furthermore, the spacer 200 is more likely to absorb the swelling of the prismatic secondary battery 100. The elastic modulus of the first portion 210 may be 1.5 MPa or more, or may be 3.0 MPa or more. By setting the elastic modulus of the first portion 210 to a predetermined value or more, the spacer 200 is more likely to return to its original shape when the prismatic secondary battery 100 is discharged. Furthermore, when the prismatic secondary battery 100 swells, the spacer 200 rebounds, making it easier to suppress the swelling. The elastic modulus of the first portion 210 can be adjusted, for example, by the material and structure (e.g., the number, size, shape, and arrangement of the protrusions 213, and the area S of the contact region CA) described below.

[0035] In this specification, "elastic modulus" refers to a value determined as follows. First, a test piece is prepared in which a pair of surfaces perpendicular to the thickness direction X are each 5 cm x 5 cm square, and the initial thickness (mm) is measured with a micrometer. Next, using a conventionally known compression testing device, the test piece is compressed in the thickness direction X at a constant rate under the condition of a compression rate of 30 N / min (12 kPa / min) until the compressive load per unit area of ​​the test piece reaches 3.9 MPa, and the compressive load (MPa) and thickness after compression (mm) are measured. Next, the compressibility (%) calculated from the compressive load (MPa) and the thickness after compression (mm) by (initial thickness - thickness after compression) (mm) / initial thickness (mm) x 100 is plotted on the horizontal axis, and the compressive load (N / mm) is plotted on the horizontal axis. 2 A compression load-compression ratio curve (FS curve) is created with the vertical axis indicating the compressibility (= MPa). FIG. 5 is a schematic FS curve. As shown in FIG. 5, the slope of the approximation line A of the FS curve (horizontal axis: compressibility, vertical axis: compressive load) in the range of compressibility from 1 to 20% is taken as the modulus of elasticity (MPa). The smaller the modulus of elasticity, the softer the material and the easier it is to elastically deform in the thickness direction X (arrangement direction X).

[0036] Considering the range of the elastic modulus, it is preferable that the first portion 210 be made of a polymer material. Examples of polymer materials include rubbers (thermosetting elastomers) such as silicone rubber, fluororubber, urethane rubber, natural rubber, styrene butadiene rubber, butyl rubber, ethylene propylene rubber (EPM, EPDM), butadiene rubber, isoprene rubber, and norbornene rubber. It is preferable that the first portion 210 be made of rubber. Among these, silicone rubber, fluororubber, and EPDM are preferable.

[0037] 6(A) and 6(B) are schematic diagrams of the first portion 210, where FIG. 6(A) is a plan view of the rear surface 210Rr (first YZ plane) perpendicular to the thickness direction X (arrangement direction X), and FIG. 6(B) is a cross-sectional view of the thickness direction X. As shown in FIG. 6(B), in this embodiment, the first portion 210 has a protrusion structure. The first portion 210 is configured to include a flat base portion 216 and a plurality of protrusions 213 protruding from the base portion 216 in the arrangement direction X. By providing the first portion 210 with a protrusion structure, it becomes easier to satisfy the elastic modulus range described above, and the elastic function can be stably exhibited even after charge / discharge cycles.

[0038] As can be seen from FIGS. 6A and 6B, the base portion 216 extends along the front surface (second YZ plane) of the first portion 210. Here, the base portion 216 is a portion that does not have voids. The base portion 216 is a non-porous (solid) portion. As shown in FIG. 6B, the base portion 216 is provided on the surface facing the second portion 220 (the front surface in FIG. 6B). However, in other embodiments, the base portion 216 may be provided on the surface facing the long side wall 12b of the prismatic secondary battery 100. Multiple protrusions 213 protrude from the base portion 216 along the thickness direction X (arrangement direction X). The presence of the base portion 216 facilitates alignment with the second portion 220, improving productivity and workability when integrating the spacer 200. The thickness (length in the arrangement direction X) of the base portion 216 is preferably 0.1 mm or more, more preferably 0.3 mm or more. The thickness of the base portion 216 is preferably 5 mm or less, and more preferably 2 mm or less.

[0039] It is preferable that the height (length in the vertical direction Z) and / or width (length in the long side direction Y) of the base portion 216 approximately match the height and / or width of the long side wall 12b of the prismatic secondary battery 100. This makes it easier to align it with the prismatic secondary battery 100, improving the productivity and workability of the battery pack 500.

[0040] The multiple protrusions 213 are integral with the base portion 216. The multiple protrusions 213 here have the same size, shape, etc. The protrusions 213 are regularly arranged in the YZ plane. Gaps 211 are provided between the protrusions 213 in the YZ plane. The protrusions 213 here extend from the base portion 216 toward the long side wall 12b of the prismatic secondary battery 100. The protrusions 213 here have an outer shape of a truncated cone. The cross-sectional shape of the protrusions 213 in the thickness direction X (arrangement direction X) is preferably trapezoidal, as shown in FIG. 6(B). This prevents the protrusions from collapsing and their elastic function from decreasing with charge / discharge cycles. Note that the protrusions 213 here are non-porous (solid structure), but may have a hollow portion inside.

[0041] As shown in Fig. 6(B), the protrusions 213 have contact areas CA at their tip ends in the thickness direction X (arrangement direction X) that come into direct contact with (abut against) the prismatic secondary battery 100. As shown in Fig. 6(A), the contact areas CA of each protrusion 213 are circular in plan view. Although not particularly limited, when the material of the first portion 210 is EPDM or silicone rubber, the area S of the contact area CA of one protrusion 213 is 1.5 mm 2 More than 3mm is preferable. 2 The above is more preferable. In addition, the area S of the contact area CA of one protrusion 213 is 100 mm 2 The sum of the areas S of the plurality of protrusions 213 (total area) is preferably less than the unit area (25 cm ) of the first portion 210. 2 ) per 1.2-18cm 2 / 25cm 2 is preferable, 1.5 to 15 cm 2 / 25cm 2 is more preferable. By setting the area S to a predetermined value or more, it is possible to suppress a decrease in elastic function. By setting the area S to a predetermined value or less, it is easy to adjust the elastic modulus of the first portion 210 to fall within the above range. The first portion 210 may have a plurality of hollow portions extending along the arrangement direction X, as will be described in a second embodiment later, for example.

[0042] The first portion 210 may have lower heat resistance than the second portion 220. For example, the heat resistance classification of the first portion 210 based on JIS K 6380 (2014) (see FIG. 7) may be E or lower (i.e., any of A to E), or D or lower (i.e., any of A to D). As shown in FIG. 7, in JIS K 6380 (2014), heat resistance is classified into classifications A to K. A is the lowest heat resistance, and K is the highest heat resistance. In particular, when the heat resistance classification of the first portion 210 is C or lower (upper limit test temperature is 125°C or lower) or B or lower (upper limit test temperature is 100°C or lower), it is preferable to provide the second portion 220, and the effects of the technology disclosed herein are exerted at a high level.

[0043] The second portion 220 is interposed between the first portion 210 and the prismatic secondary battery 100 in the arrangement direction X. If the first portion 210 has low heat resistance, providing the second portion 220 makes the first portion 210 less susceptible to the heat generated by the prismatic secondary battery 100 during charging and discharging. This makes it possible to suppress thermal degradation of the first portion 210. Furthermore, even if the temperature of a prismatic secondary battery 100 rises, the heat can be prevented from being transmitted to adjacent prismatic secondary batteries 100.

[0044] As shown in Fig. 4, the second portion 220 includes a porous portion 222. This allows the prismatic secondary battery 100 to be stably pressed with a predetermined restraining load even when the prismatic secondary battery 100 expands and contracts during charging and discharging, and allows the load necessary to maintain performance to be stably applied. Here, the second portion 220 is made up of the porous portion 222. However, the second portion 220 may also include portions other than the porous portion 222 (for example, a non-porous filling portion, etc.).

[0045] The porous portion 222 is porous (sponge-like) with many small holes arranged randomly. This is different from a pore structure such as that described in the second embodiment described later, that is, a structure having a plurality of hollow portions regularly arranged along a predetermined direction (for example, a honeycomb structure). The porous portion 222 has pores with a diameter of 2 mm or less, for example, arranged in a unit volume (12,500 mm).3 It is preferable that the number of pores per particle is 100 or more. The pores may be completely independent or may be partially interconnected, or may be interconnected in the form of a three-dimensional network, for example.

[0046] In this embodiment, the porous portion 222 is primarily made of a material that has a predetermined heat resistance and elasticity. That is, the porous portion 222 is primarily made of a material that satisfies all of the following criteria: (1) a heat resistance classification (see FIG. 7) based on JIS K 6380 (2014) of E or higher; and (2) an elastic modulus of 0.02 MPa or higher and 0.9 MPa or lower. This allows air to be contained within the second portion 220, thereby providing both heat resistance and expansion and absorption properties. In this specification, the term "primary material" refers to a material that accounts for 50% by mass or more of the porous portion 222, preferably 70% by mass or higher, and more preferably 80% by mass or higher, when the entire porous portion 222 is taken as 100% by mass. Hereinafter, a material that satisfies the above criteria (1) and (2) and accounts for 50% by mass or higher may be referred to as the "primary material."

[0047] As mentioned above, JIS K 6380 (2014) classifies heat resistance into categories A to K. Category A indicates the lowest heat resistance, while category K indicates the highest. As shown in Figure 7, a heat resistance category of E or higher means that, when subjected to continuous heat aging for 72 hours using the AA-2 forced circulation heat aging tester (crosswind type) in the accelerated aging test method A, the upper limit test temperature at which the following requirements are satisfied is 175°C or higher: (a) the "tensile strength change rate" based on JIS K 6251 is within ±30%; (b) the "elongation change rate at break" based on JIS K 6251 is within −50%; and (c) the "hardness change" based on JIS K 6253-2, 3 is within ±15%.

[0048] By setting the heat resistance category of the main material to E or higher, high thermal insulation can be imparted to the second portion 220, and heat transfer to adjacent prismatic secondary batteries 100 can be suppressed, even if the prismatic secondary batteries 100 have high capacity and generate a lot of heat. Furthermore, since the main material is less likely to burn when exposed to high temperatures, it is easy to maintain its shape. This suppresses chain heat generation among the prismatic secondary batteries 100, and prevents the entire battery pack 500 from becoming excessively hot. From the above perspective, the heat resistance category is preferably F or higher (upper limit test temperature is 200°C or higher), and even more preferably G or higher (upper limit test temperature is 225°C or higher). It is preferable that the heat resistance category of the main material has a larger alphabet (closer to K) than the heat resistance category of the first portion 210.

[0049] Furthermore, by having the modulus of elasticity of the main material satisfy the above range, even if the prismatic secondary battery 100 has a high capacity and is prone to swelling, the swelling can be appropriately absorbed, and performance degradation (e.g., Li deposition) caused by an increase in the inter-electrode distance between the positive and negative electrodes of the prismatic secondary battery 100 can be suppressed. From the above viewpoints, the modulus of elasticity of the main material is preferably 0.5 MPa or less, more preferably 0.3 MPa or less, and particularly preferably 0.2 MPa or less. The modulus of elasticity of the main material is preferably lower than the modulus of elasticity of the first portion 210. In other words, the main material (or the porous portion 222 containing the main material) is preferably softer than the first portion 210 and more easily elastically deforms in the thickness direction X. The modulus of elasticity of the main material can be adjusted, for example, by the material, structure, porosity, etc., which will be described later.

[0050] It is more preferable that the main material be left to stand for two hours after the compression test for determining the elastic modulus described above, and the thickness measured with a micrometer, such that the thickness after standing for two hours is within -20% of the initial thickness. This makes it easier for the second portion 220 to return to its original shape when the prismatic secondary battery 100 repeatedly contracts and expands with charge / discharge cycles. It also makes it easier to absorb the swelling of the prismatic secondary battery 100.

[0051] The main material is preferably a material that retains its shape even when heated to 800°C or higher. The main material is preferably a rubber such as silicone rubber or fluororubber. Silicone rubber is particularly preferred. The porous portion 222 (here, the same as the second portion 220) is preferably made of rubber. The porous portion 222 preferably contains silicone rubber. The porous portion 222 is preferably made of silicone rubber, with the silicone rubber accounting for 50% or more by mass, more preferably 70% or more by mass, even more preferably 80% or more by mass, and particularly preferably made of silicone rubber (accounting for 95% or more by mass). The porous portion 222 may contain other resin materials (for example, polymeric materials such as those exemplified as the constituent materials of the first portion 210), inorganic fillers (for example, ceramics such as alumina), various additives, etc.

[0052] The porous portion 222 may be a commercially available product or may be produced by a conventional method. Silicone rubber foam (silicone sponge) can be produced, for example, by heating a silicone material with a chemical foaming agent dispersed therein to decompose the chemical foaming agent with heat, and the gas generated during the decomposition forms interconnected pores (open cells) in a three-dimensional network.

[0053] The porosity of the porous portion 222 is preferably 20% by volume or more, more preferably 25% by volume or more, and particularly preferably 50% by volume or more. This allows the expansion and absorption properties of the spacer 200 to be improved. From the viewpoint of durability, the porosity of the porous portion 222 may be 95% by volume or less, or 90% by volume or less. In this specification, the term "porosity" refers to the total pore volume (cm) obtained by measurement with a mercury porosimeter. 3 ) to the apparent volume (cm 3 ) and multiplied by 100.

[0054] In one preferred embodiment, for example, when the spacer 200 is assembled into the battery pack 500 and compressed, a portion of the first portion 210 is disposed within the second portion 220. In one example, the first portion 210 has one or more protrusions, the second portion 220 has recesses corresponding to the protrusions, and the protrusions of the first portion 210 are disposed within the recesses of the second portion 220. More specifically, for example, a portion of the protrusion 213 of the first portion 210 (a portion adjacent to the second portion 220) is embedded in the second portion 220. Alternatively, in another example, the opposite to the above, the second portion 220 has one or more protrusions, the first portion 210 has recesses corresponding to the protrusions, and the protrusions of the second portion 220 are disposed within the recesses of the first portion 210. More specifically, for example, the convex portions of the second portion 220 penetrate between the protruding portions 213 of the first portion 210 (the gaps 211). This improves the integrity of the first portion 210 and the second portion 220, preventing misalignment of the stack. Furthermore, since the first portion 210 and the second portion 220 partially overlap in the thickness direction X, the spacer 200 can be made thinner, and the volumetric energy density of the battery pack 500 can be improved.

[0055] The battery pack 500 can be used for a variety of purposes, but is particularly suitable for use in applications requiring high capacity, such as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car, truck, etc. The type of vehicle is not particularly limited, and examples thereof include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and a battery electric vehicle (BEV).

[0056] Second Embodiment Figures 8(A) and (B) show 1st part 8A is a plan view of a plane (first YZ plane) perpendicular to the thickness direction X (arrangement direction X), and FIG. 8B is a plan view of the plane (first YZ plane) perpendicular to the thickness direction X (arrangement direction X). 88A is a longitudinal cross-sectional view taken along line VIIIB-VIIIB in FIG. 8A. The second embodiment is similar to the first embodiment described above, except that the spacer includes a first portion 210a instead of the first portion 210. The first portion 210a has a flat plate-like outer shape, similar to the first portion 210 of the first embodiment. As shown in FIG. 8A, the first portion 210a of this embodiment has a porous structure. By making the first portion 210a porous, the elastic modulus range described above can be easily satisfied, and the elastic function can be stably exhibited even after charge / discharge cycles. Furthermore, since the multiple hollow portions 212 extend along the thickness direction X (arrangement direction X), the structure can be maintained relatively stably, and the deterioration of the elastic function can be suppressed, compared to, for example, a case in which the multiple hollow portions 212 extend perpendicular to the arrangement direction X.

[0057] The first portion 210a is configured to include partition walls (ribs) 214 extending along the thickness direction X (arrangement direction X) and a plurality of hollow portions 212 that are partitioned by the partition walls 214 and regularly arranged in the thickness direction X (arrangement direction X). Here, the first portion 210a further includes a base portion 216a. The properties of the base portion 216a may be similar to those of the base portion 216 of the first embodiment. However, the base portion 216a is not essential and may be omitted in other embodiments.

[0058] The partition walls 214 form the framework of the first portion 210a. As shown in FIG. 8A, the partition walls 214 are regularly arranged on the rear surface (first YZ plane). The partition walls 214 extend (from the front side to the back side in FIG. 8A) along the thickness direction X (arrangement direction X). The partition walls 214 separate the plurality of hollow portions 212.

[0059] The plurality of hollow portions 212 are partitioned by partition walls 214 and are regularly arranged along the thickness direction X (arrangement direction X). The plurality of hollow portions 212 are mutually independent here. This differs from a porous (sponge-like) structure having voids that communicate in a three-dimensional network. Although not particularly limited, the size (volume) of one hollow portion 212 is 1 mm 3The hollow portion 212 has a hexagonal shape in the YZ plane view. That is, the hollow portion 212 has a hexagonal column shape along the thickness direction X.

[0060] As shown in FIG. 8(B), one end (the front end in FIG. 8(B)) of hollow portion 212 in thickness direction X (arrangement direction X) is closed. Here, the surface of hollow portion 212 facing second portion 220 is closed by base portion 216a. The thickness (length in arrangement direction X) of base portion 216a does not have to be uniform in the YZ plane, and there may be partially thick or thin portions. The area of ​​base portion 216a in the YZ plane may be equal to or greater than the area in the YZ plane where partition wall 214 exists.

[0061] The first portion 210a has a comb-like shape in a cross section in the thickness direction X. By closing one end of the hollow portion 212 in this manner, it becomes easier to integrate it with the second portion 220, improving workability. Meanwhile, as shown in FIG. 8(A), the other end (rear end) of the hollow portion 212 in the thickness direction X (arrangement direction X) is open. Here, the surface facing the long side wall 12b of the prismatic secondary battery 100 is open. The first portion 210a has a non-through hole structure. However, regardless of whether the base portion 216a is included, the hollow portion 212 may be a through hole with both ends in the thickness direction X (arrangement direction X) open (opened). The hollow portion 212 may have a polygonal prism through hole structure (more specifically, a hexagonal prism through hole structure) or a circular through hole structure. In this specification, the term "pore structure" refers to a general structure having a plurality of hollow portions 212 regularly arranged along the thickness direction X (arrangement direction X).

[0062] Here, the first portion 210a has a honeycomb structure. This makes it easier to maintain the hollow portions 212 even after repeated charge-discharge cycles, and the elastic function can be stably exhibited even after the charge-discharge cycles. In this specification, the term "honeycomb structure" refers to a structure that is included in the "pore structure," and is not limited to a case where the shape of the hollow portions 212 in the YZ plane view is hexagonal, but refers generally to a three-dimensional space-filling structure in which three-dimensional shapes are arranged without gaps.

[0063] In a plane (YZ plane) perpendicular to the thickness direction X (arrangement direction X), the ratio of the total area of ​​the plurality of hollow portions 212 to the entire area of ​​the first portion 210a is preferably 0.25 or more, and more preferably 0.35 to 0.8. By setting this ratio to a predetermined value or more, the prismatic secondary battery 100 becomes more easily crushed when it expands, and the expansion of the prismatic secondary battery 100 is more easily absorbed. By setting this ratio to a predetermined value or less, the hollow portions 212 can be stably maintained, and the durability of the first portion 210 can be improved.

[0064] In this embodiment, the above-mentioned "total area (total area) of the areas S of the plurality of protrusions 213" can be read as "total area S of the contact region of the entire partition wall 214."

[0065] Hereinafter, several examples of the present invention will be described, but it is not intended that the present invention be limited to these examples.

[0066] <Preparation of Battery Pack 1> First, a plurality of lithium ion secondary batteries were prepared. Next, spacers including a first portion and a second portion (Examples 1 to 7, Comparative Examples 1 to 3), and a spacer consisting only of the second portion (Comparative Example 4) were prepared. In Examples 1 to 7 and Comparative Examples 1 to 3, the thickness of the first portion and the second portion was 0.075 times the thickness of the lithium ion secondary battery (7.5% of the thickness of the lithium ion secondary battery).

[0067] The first portions of the spacers of Examples 1 to 7 and Comparative Examples 1 to 3 are made of the materials shown in Table 1 and have the shapes shown in Table 1. The first portions of the spacers of Examples 1 to 7 and Comparative Examples 1 to 3 each have the modulus of elasticity shown in Table 1. For example, the first portions of the spacers of Examples 1 to 5 and 7 and Comparative Examples 1 to 3 are made of EPDM and have a protruding structure including a flat, non-porous (solid structure) base portion and a plurality of protruding portions extending in the thickness direction from the base portion. The first portion of the spacer of Example 6 is made of silicone rubber and has a honeycomb structure including partition walls extending along the thickness direction and a plurality of hollow portions partitioned by the partition walls and regularly arranged in the thickness direction.

[0068] The second portions of the spacers in Examples 1 to 7 and Comparative Examples 1 to 4 are made of the materials shown in Table 1. The second portions of the spacers in Examples 1 to 7 and Comparative Examples 1 to 4 are made of materials having the porosity, heat resistance class, and elastic modulus shown in Table 1. The second portions of the spacers in Examples 1 to 7 and Comparative Examples 2 and 4 are made of porous portions. The second portions of the spacers in Examples 1 to 6 and Comparative Example 4 are made of porous flat-plate silicone rubber foam. The second portion of the spacer in Comparative Example 1 is made of non-porous (solid structure) flat-plate silicone rubber.

[0069] <Preparation of battery pack 2> Next, the lithium ion secondary battery and the spacer were sandwiched between a pair of restraining jigs in the arrangement direction, and the spacer was restrained so that its thickness was 80% of that before restraint, to prepare a test battery. Then, the distance between the pair of restraining jigs (initial thickness) was measured.

[0070] <Cycle test> In a temperature environment of 40°C, the SOC (State of Charge) of the secondary battery was adjusted to 15%, and the battery was charged at a constant current and constant voltage at a charge rate of 0.2C up to an SOC of 95%, followed by a 5-minute pause. One charge-discharge cycle consisted of a constant current and constant voltage discharge at a discharge rate of 0.5C up to an SOC of 15%, followed by a 90-minute pause. This cycle was repeated 200 times.

[0071] <Evaluation of the thickness change of the battery pack> After the cycle test, the distance between the pair of restraining jigs (thickness after cycle) was measured again and compared with the initial thickness. The results are shown in Table 1. In Table 1, when the thickness after cycle is within 1.03 times the initial thickness, it is indicated as "◎", when it exceeds 1.03 times and is within 1.05 times the initial thickness, it is indicated as "〇", and when it exceeds 1.05 times the initial thickness, it is indicated as "×". Note that the closer the above numerical value is to 1, the more the swelling of the test battery including the spacer is suppressed.

[0072] <Determination of the presence or absence of Li deposition> After the cycle test, the lithium-ion secondary battery was disassembled, and the presence or absence of Li deposition on the negative electrode and separator of the electrode body was visually confirmed. The results are shown in Table 1.

[0073] <Determination of flame resistance> The lithium-ion secondary battery located at the center in the arrangement direction in the battery pack was forcibly thermally runaway by local heating, and the flame time of the adjacent lithium-ion secondary battery was measured. The results are shown in Table 1. In Table 1, when it did not flame for 20 minutes or more (specifically, no smoking and ignition were observed), it is indicated as "〇", and when it flamed in less than 20 minutes (specifically, smoking and / or ignition were observed), it is indicated as "×".

[0074]

Table 1

[0075] As shown in Table 1, in Comparative Examples 3 and 4, the thickness after cycle was relatively large. As a reason for this, in Comparative Example 3, it is considered that the swelling of the secondary battery could not be absorbed because the elastic modulus of the second part of the spacer was as high as 15 MPa. Further, in Comparative Example 4, it is considered that the swelling of the secondary battery could not be absorbed because the spacer did not include the first part having a predetermined elastic modulus.

[0076] Furthermore, as shown in Table 1, Li deposition was observed after the cycle test in Comparative Example 4. The reason for this is thought to be that the load applied to the secondary battery was insufficient because the spacer did not include the first portion with the predetermined elastic modulus, which increased the inter-electrode distance between the positive and negative electrodes and caused uneven charge-discharge reactions.

[0077] Furthermore, as shown in Table 1, Comparative Examples 1 and 2 had relatively low fire spread resistance. The reason for this is thought to be that in Comparative Example 1, the second portion of the spacer was not porous, which allowed heat to be easily transferred to the adjacent secondary battery. Also, in Comparative Example 2, the second portion of the spacer was in heat resistance category B, which meant that heat resistance was insufficient, which allowed heat to be easily transferred to the adjacent secondary battery.

[0078] In comparison with these comparative examples, in Examples 1 to 7, the thickness after cycling was relatively small, and no Li deposition was observed. Furthermore, the fire spread resistance was relatively high. The reason for this is thought to be that the first portion of the spacer satisfied the predetermined elastic modulus, and the second portion included a porous portion, and the porous portion was composed of a material that satisfied the predetermined elastic modulus and heat resistance classification, thereby imparting heat resistance and swelling absorption properties to the spacer. Specifically, compared to when the second portion did not have a porous portion or when the porous portion did not satisfy the heat resistance classification, heat transfer to adjacent secondary batteries was relatively suppressed, and swelling of the secondary batteries after charge / discharge cycles was relatively more effectively absorbed than when the second portion did not satisfy the above elastic modulus. These results demonstrate the significance of the technology disclosed herein.

[0079] 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 common general technical knowledge 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 the following modifications, and it is also possible 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.

[0080] (1) For example, in the first and second embodiments described above, the first portion 210 and the second portion 220 each have a flat plate-like outer shape and have approximately the same area in the plane (YZ plane) perpendicular to the thickness direction X (arrangement direction X). However, this is not limited to this. The first portion 210 and the second portion 220 may have different areas in the YZ plane. In a modified example, the area in the YZ plane of the first portion 210 is preferably smaller than the area in the YZ plane of the second portion 220. If the area of ​​the second portion 220 is large, the influence of heat generation in the prismatic secondary battery 100 can be further reduced, and thermal degradation of the first portion 210 can be suppressed to a high level.

[0081] (2) For example, in the first embodiment described above, the first portion 210 had a protrusion structure. The multiple protrusions 213 had a truncated cone shape, and the contact area CA of each protrusion 213 was circular in plan view. However, this is not limited to this. The external shape of the protrusion 213 may be cylindrical or polygonal (triangular, rectangular, etc.). The contact area CA may be circular or polygonal (triangular, rectangular, etc.) in plan view.

[0082] (3) For example, in the second embodiment described above, the multiple hollow portions 212 of the first portion 210a were independent of one another. However, this is not limited to this. The multiple hollow portions 212 may be connected by holes penetrating the partition wall 214. In other words, the first portion 210a may have holes that connect the multiple hollow portions 212. According to this embodiment, air can flow in and out of the multiple hollow portions 212 smoothly, and a decrease in elasticity due to the so-called suction cup effect can be suppressed.

[0083] (4) For example, in the second embodiment described above, the first portion 210a has a honeycomb structure, and the plurality of hollow portions 212 included in the first portion 210 have a hexagonal shape in a YZ plane view. However, this is not limited to this. The hollow portions 212 do not have to have a honeycomb structure. The hollow portions 212 may be randomly arranged. Furthermore, the shape of the hollow portions 212 in a YZ plane view may be a shape other than a hexagon, such as a circle, a triangle, or a rectangle. Furthermore, the hollow portions 212 may be divided in the middle of the space in the thickness direction X (arrangement direction X).

[0084] 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 and a spacer arranged between adjacent prismatic secondary batteries in the arrangement direction, wherein the spacer includes a first portion and a second portion stacked in the arrangement direction, the first portion having an elastic modulus of 1 MPa or more and 10 MPa or less, and the second portion including a porous portion, the porous portion being made up of 50 mass % or more of a material that satisfies all of the following conditions: 1) heat resistance classification based on JIS K 6380 (2014) of E or higher; and (2) the elastic modulus being 0.02 MPa or more and 0.9 MPa or less, wherein the elastic modulus refers to a value calculated as the slope of an approximation line in a compression ratio range of 1 to 20% from a compression load-compression ratio curve (horizontal axis: compression ratio, vertical axis: compression load) created by compressing the battery pack in the arrangement direction at a compression rate of 12 kPa / min until a compression load of 3.9 MPa is reached. Item 2: The battery pack according to item 1, wherein the silicone rubber accounts for 50% by mass or more of the entire porous portion. Item 3: The battery pack according to item 1 or 2, wherein the elastic modulus of the material constituting the porous portion is 0.02 MPa or more and 0.2 MPa or less. Item 4: The battery pack according to any one of Items 1 to 3, wherein the porosity of the porous portion is 25% by volume or more. Item 5: The battery pack according to any one of Items 1 to 4, wherein the porosity of the porous portion is 50% by volume or more. Item 6: The battery pack according to any one of items 1 to 5, wherein the area of ​​a surface of the first portion perpendicular to the arrangement direction is equal to or smaller than the area of ​​a surface of the second portion perpendicular to the arrangement direction. Item 7: The battery pack according to any one of items 1 to 6, wherein a part of the first portion is disposed within the second portion. Item 8: The battery pack according to any one of items 1 to 7, wherein the first portion and the second portion are integrated together by a uniting member. [Explanation of symbols]

[0085] 10 Battery case 20 Electrode body 100 Prismatic secondary battery 200 spacer 210, 210a Part 1 212 Hollow part 213 Protrusion 214 Bulkhead 216, 216a base 220 Part 2 300 Restraint mechanism 500 battery packs

Claims

1. a plurality of prismatic secondary batteries arranged along a predetermined arrangement direction; a spacer disposed between adjacent prismatic secondary batteries in the arrangement direction; A battery pack comprising: the spacer includes a first portion and a second portion stacked in the arrangement direction, The first portion has an elastic modulus of 1 MPa or more and 10 MPa or less, the second portion includes a porous portion, The porous portion satisfies the following conditions: (1) The heat resistance classification based on JIS K 6380 (2014) is E or higher; (2) The elastic modulus is 0.02 MPa or more and 0.9 MPa or less; The material satisfying all of the above accounts for 50 mass % or more of the total, Here, the elastic modulus refers to a value determined as the slope of an approximate straight line in the range of compressibility of 1 to 20% from a compression load-compressibility curve (horizontal axis: compressibility, vertical axis: compressive load) prepared by compressing the material in the orientation direction at a compression rate of 12 kPa / min until the compressive load reaches 3.9 MPa, an area of ​​a surface of the first portion perpendicular to the arrangement direction is equal to or smaller than an area of ​​a surface of the second portion perpendicular to the arrangement direction.

2. The porous portion is made of silicone rubber, and the silicone rubber accounts for 50% by mass or more of the entire porous portion. The battery pack according to claim 1 .

3. The elastic modulus of the material constituting the porous portion is 0.02 MPa or more and 0.2 MPa or less. The battery pack according to claim 1 or 2.

4. The porosity of the porous portion is 25% by volume or more. The battery pack according to claim 1 or 2.

5. The porosity of the porous portion is 50% by volume or more. The battery pack according to claim 1 or 2.

6. A portion of the first portion is disposed within the second portion. The battery pack according to claim 1 or 2.

7. The first portion and the second portion are integrated by a uniting member. The battery pack according to claim 1 or 2.

8. a plurality of prismatic secondary batteries arranged along a predetermined arrangement direction; a spacer disposed between adjacent prismatic secondary batteries in the arrangement direction; A battery pack comprising: the spacer includes a first portion and a second portion stacked in the arrangement direction, the first portion includes a flat base portion and a plurality of protrusions protruding from the base portion in the arrangement direction, each of the protrusions having a truncated cone shape and a trapezoidal cross section in the thickness direction, and has an elastic modulus of 1 MPa or more and 10 MPa or less; the second portion includes a porous portion, The porous portion satisfies the following conditions: (1) The heat resistance classification based on JIS K 6380 (2014) is E or higher; (2) The elastic modulus is 0.02 MPa or more and 0.9 MPa or less; The material satisfying all of the above accounts for 50 mass % or more of the total, Here, the elastic modulus refers to a value calculated as the slope of an approximate straight line in the range of compression ratio from 1 to 20% from a compression load-compression ratio curve (horizontal axis: compression ratio, vertical axis: compression load) prepared by compressing the battery in the arrangement direction at a compression rate of 12 kPa / min until the compression load reaches 3.9 MPa.

9. a plurality of prismatic secondary batteries arranged along a predetermined arrangement direction; a spacer disposed between adjacent prismatic secondary batteries in the arrangement direction; A battery pack comprising: the spacer includes a first portion and a second portion stacked in the arrangement direction, the first portion has a pore structure including a plurality of hollow portions extending along the arrangement direction, and has an elastic modulus of 1 MPa or more and 10 MPa or less; the second portion includes a porous portion, The porous portion satisfies the following conditions: (1) The heat resistance classification based on JIS K 6380 (2014) is E or higher; (2) The elastic modulus is 0.02 MPa or more and 0.9 MPa or less; The material satisfying all of the above accounts for 50 mass % or more of the total, Here, the elastic modulus refers to a value calculated as the slope of an approximate straight line in the range of compression ratio from 1 to 20% from a compression load-compression ratio curve (horizontal axis: compression ratio, vertical axis: compression load) prepared by compressing the battery in the arrangement direction at a compression rate of 12 kPa / min until the compression load reaches 3.9 MPa.

10. a plurality of prismatic secondary batteries arranged along a predetermined arrangement direction; a spacer disposed between adjacent prismatic secondary batteries in the arrangement direction; A battery pack comprising: the spacer includes a first portion and a second portion stacked in the arrangement direction, the first portion includes a plurality of partition walls extending along the arrangement direction and a plurality of hollow portions that are partitioned by the partition walls and are regularly arranged in the arrangement direction, and has an elastic modulus of 1 MPa or more and 10 MPa or less; the second portion includes a porous portion, The porous portion satisfies the following conditions: (1) The heat resistance classification based on JIS K 6380 (2014) is E or higher; (2) The elastic modulus is 0.02 MPa or more and 0.9 MPa or less; The material satisfying all of the above accounts for 50 mass % or more of the total, Here, the elastic modulus refers to a value calculated as the slope of an approximate straight line in the range of compression ratio from 1 to 20% from a compression load-compression ratio curve (horizontal axis: compression ratio, vertical axis: compression load) prepared by compressing the battery in the arrangement direction at a compression rate of 12 kPa / min until the compression load reaches 3.9 MPa.

11. a plurality of prismatic secondary batteries arranged along a predetermined arrangement direction; a spacer disposed between adjacent prismatic secondary batteries in the arrangement direction; A battery pack comprising: the spacer includes a first portion and a second portion stacked in the arrangement direction, The first portion has an elastic modulus of 1 MPa or more and 10 MPa or less, the second portion includes a porous portion, The porous portion satisfies the following conditions: (1) The heat resistance classification based on JIS K 6380 (2014) is E or higher; (2) The elastic modulus is 0.02 MPa or more and 0.9 MPa or less; The material satisfying all of the above accounts for 50 mass % or more of the total, Here, the elastic modulus refers to a value determined as the slope of an approximate straight line in the range of compressibility of 1 to 20% from a compression load-compressibility curve (horizontal axis: compressibility, vertical axis: compressive load) prepared by compressing the material in the orientation direction at a compression rate of 12 kPa / min until the compressive load reaches 3.9 MPa, the first portion has a protrusion, the second portion has a recess corresponding to the protrusion, and the protrusion of the first portion is disposed within the recess of the second portion.

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