Battery pack

Abstract

To provide a battery pack including a spacer that can suppress or absorb swelling of a secondary battery.SOLUTION: A battery pack disclosed herein includes: a plurality of rectangular secondary batteries that are disposed along a predetermined arrangement direction X; and a spacer that is disposed between the rectangular secondary batteries that are adjacent in the arrangement direction X. The spacer includes an elastic part 210. The elastic part 210 satisfies both following conditions: (1) an elastic modulus in the arrangement direction X is 1 MPa or more and 10 MPa or less and (2) a constant load compression ratio is 35% or more and 70% or less.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

[0002] Conventionally, in power sources for vehicle driving and the like, a battery pack formed by electrically connecting a plurality of secondary batteries (single cells) has been widely used for achieving high output. As related prior art documents, Patent Documents 1 to 3 can be cited.

[0003] For example, Patent Document 1 discloses a battery pack including a plurality of secondary batteries arranged along a predetermined arrangement direction, and a spacer arranged between adjacent secondary batteries in the arrangement direction and having through holes extending along a direction orthogonal to the arrangement direction and uniformly dispersed throughout the cross section. Patent Document 1 describes that by dispersedly arranging through holes inside the spacer, elasticity is imparted to the spacer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, secondary batteries mounted on vehicles and the like have been increasingly becoming higher in capacity. According to the study by the present inventors, when applying the above technology to a battery pack equipped with a high-capacity secondary battery, there is still room for improvement. That is, in a high-capacity secondary battery, as the amount of the active material in the battery case increases, it becomes easier to expand with charge and discharge cycles. At this time, if the spacer is too soft, the secondary battery cannot be appropriately pressed after the charge and discharge cycles, and the secondary battery becomes likely to expand. On the other hand, if the spacer is too hard, it becomes difficult to absorb the expansion when the secondary battery expands. As a result, expansion of the entire battery pack and performance deterioration of the secondary battery (for example, increase in resistance) are likely to occur.

[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 capable of suppressing or absorbing the expansion of a secondary battery.

Means for Solving the Problems

[0007] According to the present invention, there is disclosed a battery pack including a plurality of rectangular secondary batteries arranged along a predetermined arrangement direction, and a spacer arranged between the adjacent rectangular secondary batteries in the arrangement direction. The spacer includes an elastic portion, and the elastic portion satisfies the following conditions: (1) an elastic modulus obtained as the slope of an approximate straight line A in a range of a compression ratio of 1% to 20% from a compression load-compression ratio curve (horizontal axis: compression ratio, vertical axis: compression load) created by compressing at a compression speed of 12 kPa / min until the compression load in the arrangement direction becomes 3.9 MPa is 1 MPa or more and 10 MPa or less; (2) a constant load compression ratio obtained as the value of the horizontal axis at the intersection of the compression load-compression ratio curve and a straight line B having a slope 1.4 times that of the approximate straight line A is 35% or more and 70% or less.

[0008] In the present invention, since the spacer includes an elastic portion, even when the secondary battery expands and contracts during charging and discharging, a load can be stably applied to the secondary battery. Further, by satisfying the elastic modulus and the constant load compression ratio of the elastic portion, for example, compared with the case where the elastic portion does not satisfy the elastic modulus and / or the constant load compression ratio, the swelling of the secondary battery after the charge / discharge cycle can be relatively suppressed or absorbed. As a result, deterioration of the performance of the secondary battery can be suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0010] Hereinafter, with reference to the drawings as appropriate, some preferred embodiments of the assembled battery disclosed herein will be described. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention (for example, the general configuration and manufacturing process of an assembled battery or a rectangular secondary battery that does not characterize the present invention) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The assembled battery disclosed herein can be implemented based on the content disclosed in this specification and the common general knowledge in the relevant field.

[0011] In the following drawings, members and parts having the same function are denoted by the same reference numerals, and redundant descriptions may be omitted or simplified. Also, the notation "A to B" indicating a range in this specification includes the meaning of "A or more and B or less", as well as the meaning of "preferably greater than A" and "preferably less than B".

[0012] <First Embodiment> FIG. 1 is a perspective view schematically showing an assembled battery 500 according to an embodiment. The assembled battery 500 includes a plurality of rectangular secondary batteries 100 arranged along the arrangement direction X, and a plurality of spacers 200 arranged between the adjacent rectangular secondary batteries 100 in the arrangement direction X. The assembled battery 500 further includes a restraint mechanism 300 here. In the following description, the reference numerals L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, up, and down, respectively, and the reference numerals X, Y, and Z in the drawings represent the thickness direction, the long side direction orthogonal to the thickness direction, and the up-down direction orthogonal to the thickness direction and the long side direction of the rectangular secondary battery 100, respectively. The thickness direction X is also the arrangement direction of the rectangular secondary batteries 100. However, these are merely directions for convenience of explanation and do not limit the installation form of the assembled battery 500 in any way.

[0013] The restraint mechanism 300 is configured to apply a specified restraint pressure to a plurality of rectangular secondary batteries 100 and a plurality of spacers 200 in the arrangement direction X. Here, the restraint mechanism 300 is composed of a pair of end plates 310, a pair of side plates 320, and a plurality of screws 330. The pair of end plates 310 are arranged at both ends of the plurality of rectangular secondary batteries 100 in the arrangement direction X. The pair of end plates 310 sandwich the plurality of rectangular secondary batteries 100 and the plurality of spacers 200 in the arrangement direction X. The pair of end plates 310 are preferably made of metal. However, a part thereof 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, a part thereof may be made of resin. The pair of side plates 320 are fixed to the end plates 310 by a plurality of screws 330 so that the restraint load is approximately 10 to 15 kN, for example. Thereby, a restraint load is applied to the plurality of rectangular secondary batteries 100 and the plurality of spacers 200 from the arrangement direction X, and the assembled battery 500 is integrally held. However, the configuration of the restraint mechanism is not limited to this. The restraint mechanism 300 may include a plurality of restraint bands, binding bars, etc. instead of the side plates 320, for example.

[0015] The plurality of rectangular secondary batteries 100 are arranged side by side between the pair of end plates 310 along the arrangement direction X (in other words, the thickness direction X of the rectangular secondary battery 100). The plurality of rectangular secondary batteries 100 are preferably restrained by the restraint mechanism 300. Although not shown in FIG. 1, when the assembled battery 500 is used, the plurality of rectangular secondary batteries 100 are electrically connected by a conductive member such as a bus bar. The connection method is not particularly limited, and may be, for example, series, parallel, or multi-series multi-parallel, etc.

[0016] The rectangular secondary battery 100 is a battery capable of repeated charge and discharge. In this specification, the term "secondary battery" refers to all rechargeable power storage devices. In addition to so-called storage batteries such as lithium-ion secondary batteries and nickel-metal hydride batteries, it includes capacitors such as lithium-ion capacitors and electric double-layer capacitors. Further, the shape, size, number, arrangement, etc. of the rectangular secondary batteries 100 constituting the battery pack 500 are not limited to the embodiments disclosed herein and can be appropriately changed.

[0017] FIG. 2 is a perspective view of the rectangular secondary battery 100. FIG. 3 is a schematic longitudinal sectional view taken along line III-III of FIG. 2. As shown in FIG. 3, the rectangular secondary battery 100 includes a battery case 10, an electrode body 20, a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collector member 50, a negative electrode current collector member 60, and a non-aqueous electrolyte (not shown). The non-aqueous electrolyte may be the same as that used conventionally and is not particularly limited. The rectangular secondary battery 100 is a lithium-ion secondary battery here.

[0018] The battery case 10 is a housing that houses the electrode body 20 and the non-aqueous electrolyte. As shown in FIG. 2, the battery case 10 has an outer shape of a flat and bottomed rectangular parallelepiped (rectangular). 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, aluminum alloy, iron, iron alloy, etc. The battery case 10 includes an outer package 12 and a sealing plate (lid) 14. The battery case 10 preferably includes the outer package 12 and the sealing plate 14 as in this embodiment.

[0019] As shown in FIG. 2, the outer package 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 wall 12b is a surface facing the spacer 200. The area of the long side wall 12b is larger than the area of the short side wall 12c. The sealing plate 14 is a plate-like member that seals the opening 12h of the outer package 12. As shown in FIG. 3, the sealing plate 14 is attached to the outer package 12 so as to close the opening 12h. The sealing plate 14 faces the bottom wall 12a of the outer package 12. The sealing plate 14 is substantially rectangular. The battery case 10 is integrated by joining (preferably, welding) the sealing plate 14 to the periphery of the opening 12h of the outer package 12. The battery case 10 is hermetically sealed.

[0020] In this specification, the term "substantially rectangular" includes, in addition to a perfect rectangular shape (rectangular shape), for example, a shape in which the corners connecting the long side and the short side of the rectangular shape are R-shaped, a shape having a notch at the corner, and the like.

[0021] As shown in FIG. 3, the sealing plate 14 is provided with a liquid injection hole 15, a discharge valve 17, and two terminal lead-out holes 18 and 19. It is preferable to provide the liquid injection hole 15 and the discharge valve 17 in the sealing plate 14. The liquid injection hole 15 is for injecting a non-aqueous electrolyte after the sealing plate 14 is assembled to the outer package 12. The liquid injection hole 15 is sealed by a sealing member 16. The discharge valve 17 is configured to break when the pressure in the battery case 10 reaches a predetermined value or more and discharge the gas in the battery case 10 to the outside. The terminal lead-out holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z. The terminal lead-out holes 18 and 19 each have an inner diameter large enough to allow the positive electrode terminal 30 and the negative electrode terminal 40 before being attached to the sealing plate 14 (before caulking) to pass through.

[0022] The positive terminal 30 is disposed at one end (the left end in FIGS. 2 and 3) in the long side direction Y of the sealing plate 14. The negative terminal 40 is disposed at the other end (the right end in FIGS. 2 and 3) in the long side direction Y of the sealing plate 14. The positive terminal 30 and the negative terminal 40 are preferably attached to the sealing plate 14. As shown in FIG. 3, the positive terminal 30 and the negative terminal 40 extend from the inside to the outside of the sealing plate 14 through the terminal lead holes 18 and 19. Here, the positive terminal 30 and the negative terminal 40 are caulked to the peripheral portion surrounding the terminal lead holes 18 and 19 of the sealing plate 14 by caulking. Caulking portions 30c and 40c are formed at the ends (the lower ends in FIG. 3) on the side of the outer package 12 of the positive terminal 30 and the negative terminal 40.

[0023] As shown in FIG. 3, inside the outer package 12, the positive terminal 30 is electrically connected to the positive current collecting portion 23 of the electrode body 20 via the positive current collecting member 50. Inside the outer package 12, the negative terminal 40 is electrically connected to the negative current collecting portion 25 of the electrode body 20 via the negative current collecting member 60. The positive terminal 30 is insulated from the sealing plate 14 by the internal insulating member 80 and the gasket 90. The negative terminal 40 is insulated from the sealing plate 14 by the internal insulating member 80 and the gasket 90.

[0024] As shown in FIGS. 2 and 3, plate-shaped positive external conductive members 32 and negative external conductive members 42 are attached to the outer surface of the sealing plate 14. The positive external conductive member 32 is electrically connected to the positive terminal 30. The negative external conductive member 42 is electrically connected to the negative terminal 40. The positive external conductive member 32 and the negative external conductive member 42 are members to which conductive members such as bus bars for electrically connecting a plurality of rectangular secondary batteries 100 to each other are attached. The positive external conductive member 32 and the negative external conductive member 42 are insulated from the sealing plate 14 by the external insulating member 92. The assembled battery 500 is, for example, connected in series by electrically connecting the positive external conductive member 32 of one rectangular secondary battery 100 and the negative external conductive member 42 of the other rectangular secondary battery 100 with a bus bar or the like among adjacent rectangular secondary batteries 100.

[0025] The electrode body 20 has a positive electrode and a negative electrode. The configuration of the electrode body 20 may be the same as that of the conventional one, and there is no particular limitation. Also, the number of electrode bodies 20 arranged inside one exterior body 12 is not particularly limited, and a plurality of them may be provided. Here, the electrode body 20 is a flat wound electrode body formed by laminating a strip-shaped positive electrode and a strip-shaped negative electrode in an insulated state via a separator and winding them around a winding axis. However, in other embodiments, the electrode body 20 may be a laminated electrode body formed by stacking a plurality of rectangular positive electrodes and a plurality of 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 collecting member 50 is attached to the positive electrode current collector 23. A negative electrode current collecting member 60 is attached to the negative electrode current collector 25. The positive electrode current collecting member 50 constitutes a conduction path that electrically connects the positive electrode terminal 30 and the positive electrode of the electrode body 20. The negative electrode current collecting member 60 constitutes a conduction path that electrically connects the negative electrode terminal 40 and the negative electrode of the electrode body 20.

[0027] Here, the spacers 200 are respectively arranged between a plurality of rectangular secondary batteries 100 in the arrangement direction X. That is, in the arrangement direction X, the rectangular secondary batteries 100 and the spacers 200 are arranged alternately. However, the spacers 200 only need to be arranged between at least two adjacent rectangular secondary batteries 100 in the arrangement direction X, and do not necessarily need to be arranged between all the rectangular secondary batteries 100. Here, a pair of surfaces (both surfaces in the arrangement direction X) of the spacer 200 orthogonal to the arrangement direction X are respectively in contact (direct contact) with the long side walls 12b of the rectangular secondary battery 100. However, other members may be interposed between the rectangular secondary battery 100 and the spacer 200.

[0028] FIG. 4 is a perspective view schematically showing the spacer 200. As shown in FIG. 4, the spacer 200 includes an elastic portion 210. The spacer 200 further includes a heat insulating portion 220 here. It is preferable that the spacer 200 includes the heat insulating portion 220. However, the heat insulating portion 220 is not essential and can be omitted in other embodiments. The elastic portion 210 and the heat insulating portion 220 in FIG. 4 each have a flat outer shape. The elastic portion 210 and the heat insulating portion 220 are laminated in the arrangement direction X. The spacer 200 has a two-layer structure of one elastic portion 210 and one heat insulating portion 220 here. One of the pair of surfaces (Y-Z plane in FIG. 4) orthogonal to the thickness direction X of the elastic portion 210 abuts (contacts here) against the heat insulating portion 220, and the other abuts (contacts here) against the long side wall 12b of the battery case 10. One of the pair of surfaces (Y-Z plane in FIG. 4) orthogonal to the thickness direction X of the heat insulating portion 220 abuts (contacts here) against the elastic portion 210, and the other abuts (contacts here) against the long side wall 12b of the battery case 10.

[0029] The elastic portion 210 and the heat insulating portion 220 are preferably integrated. In particular, it is preferably integrated by an integrating member. Thereby, the lamination shift between the elastic portion 210 and the heat insulating portion 220 can be prevented. Also, the productivity and workability of the assembled battery 500 can be improved. In this specification, "integration" includes detachable fixing using an integrating member, non-detachable adhesion, etc., and fitting (mechanical joining) and integral molding without using an integrating member, etc. The elastic portion 210 and the heat insulating portion 220 may be fixed, for example, with a tape or the like as an integrating member, or may be entirely covered and wrapped with a resin sheet, a laminated film, or the like as an integrating member, or may be adhered by chemical or physical force through an adhesive or an adhesive layer (double-sided tape, etc.) as an integrating member, or may be processed as one member by fitting or integral molding without using an integrating member.

[0030] As shown in FIG. 4, the elastic portion 210 and the heat insulating portion 220 have substantially the same area in the Y-Z plane here (processing errors are acceptable). The area of the elastic portion 210 and the heat insulating portion 220 in the Y-Z plane 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. Thereby, the effects of the technology disclosed herein can be exhibited at a high level.

[0031] As shown in FIG. 4, the thickness t1 of the elastic portion 210 is preferably 5% or more, for example, 5 to 15% of the thickness (the length in the thickness direction X) of the rectangular secondary battery 100 in the state before being assembled and compressed into the assembled battery 500. The thickness t2 of the heat insulating portion 220 is preferably 2% or more, for example, 2 to 20% of the thickness (the length in the thickness direction X) of the rectangular secondary battery 100 in the state before being assembled and compressed into the assembled battery 500, and more preferably 5% or more, for example, 5 to 15%. The total of the thickness t1 and the thickness t2 is preferably 7% or more, for example, 7 to 35%, and further preferably 10% or more, for example, 10 to 30% of the thickness (the length in the thickness direction X) of the rectangular secondary battery 100.

[0032] However, the shape, size, arrangement, etc. of the elastic portion 210 and the heat insulating portion 220 can be appropriately determined according to, for example, the shape, size, capacity (degree of expansion and contraction), etc. of the rectangular secondary battery 100. For example, the spacer 200 may consist only of the elastic portion 210 or may have a structure of three or more layers. The spacer 200 may have, for example, a three-layer structure (heat insulating portion 220 / elastic portion 210 / heat insulating portion 220) in which the heat insulating portions 220 are respectively arranged on both side surfaces of the elastic portion 210 in the arrangement direction X, or conversely, may have a three-layer structure (elastic portion 210 / heat insulating portion 220 / elastic portion 210) in which the elastic portions 210 are respectively arranged on both side surfaces of the heat insulating 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 elastic portion 210 and the heat insulating portion 220.

[0033] The elastic part 210 is a part configured to be elastically deformable in the arrangement direction X. Therefore, when the rectangular secondary battery 100 expands during charging or the like and the load applied to the elastic part 210 increases, the elastic part 210 is compressed. On the other hand, when the rectangular secondary battery 100 contracts during discharging or the like and the load applied to the elastic part 210 decreases, the elastic part 210 returns to its original shape again. Thus, by providing the elastic part 210 in the spacer 200, even when the rectangular secondary battery 100 expands and contracts during charging and discharging, the rectangular secondary battery 100 can be stably pressed with a predetermined restraint load, and the load necessary for maintaining performance can be stably applied.

[0034] In this embodiment, the elastic part 210 satisfies a predetermined range of elastic modulus and constant load compression ratio, which will be described later. Thereby, the swelling of the rectangular secondary battery 100 can be suppressed or absorbed over a long period. That is, in particular, a high-capacity rectangular secondary battery 100 may swell when charged and discharged repeatedly. In such a case, when the elastic part 210 satisfies a predetermined elastic modulus, the swelling can be preferably suppressed or absorbed after the charge-discharge cycle. Furthermore, when the constant load compression ratio satisfies a predetermined range, such an effect can be maintained longer. As a result, it is possible to prevent an excessive restraint load of more than a predetermined value from being applied to the rectangular secondary battery 100, and to prevent the inter-pole distance between the positive and negative electrodes from opening and performance degradation (for example, Li deposition). Also, compared with the mode disclosed in Patent Document 3, for example, the spacer 200 can be made relatively thinner, and the volume energy density of the assembled battery 500 can be improved.

[0035] In this embodiment, the elastic modulus of the elastic part 210 is 1 MPa to 10 MPa. The smaller the value of the elastic modulus, the softer it is and the easier it is to elastically deform in the thickness direction X (arrangement direction X). The elastic modulus of the elastic part 210 is preferably 5 MPa or less, and more preferably 3.3 MPa or less. By setting the elastic modulus of the elastic part 210 to a predetermined value or less, the spacer 200 is likely to be crushed when the rectangular secondary battery 100 is charged or when the rectangular secondary battery 100 expands, and it becomes easier to absorb the expansion. As a result, as described in the examples below, the effects of the technology disclosed herein can be exerted at a high level. The elastic modulus of the elastic part 210 is preferably 1.5 MPa or more, and more preferably 3.0 MPa or more. By setting the elastic modulus of the elastic part 210 to a predetermined value or more, when the rectangular secondary battery 100 expands, it repels and it becomes easier to suppress the expansion.

[0036] In addition, in this specification, the "elastic modulus" refers to the value obtained as follows. That is, first, a test piece is prepared in which a pair of surfaces orthogonal to the thickness direction X are each in a square shape of 5 cm × 5 cm, and the initial thickness (mm) is measured with a micrometer. Next, using a conventionally known compression test device, under the condition of a compression speed of 30 N / min (12 kPa / min), the test piece is compressed at a constant speed in the thickness direction X until the compression load per unit area of the test piece reaches 3.9 MPa, and the compression load (MPa) and the thickness after compression (mm) are measured. Next, from the compression load (MPa) and the thickness after compression (mm), with the compression rate (%) obtained by (initial thickness - thickness after compression) (mm) / initial thickness (mm) × 100 on the horizontal axis and the compression load (N / mm 2 =MPa) on the vertical axis, a compression load-compression rate curve (FS curve) is created. Fig. 5 is a schematic FS curve. And, as shown in Fig. 5, the slope of the approximate straight line A in the range of 1 to 20% of the compression rate of the FS curve (horizontal axis: compression rate, vertical axis: compression load) is taken as the elastic modulus (MPa).

[0037] It is more preferable that when the elastic part 210 is left standing for 2 hours after the above compression test and the thickness is measured with a micrometer, the thickness after 2 hours of standing is within -20% of the initial thickness. Thereby, when the prismatic secondary battery 100 repeats contraction and expansion along with the charge and discharge cycles, it becomes easier to return the elastic part 210 to its original shape. Also, it becomes easier to absorb the swelling of the prismatic secondary battery 100.

[0038] In the present embodiment, the constant load compression ratio of the elastic part 210 is 35% or more and 70% or less. The constant load compression ratio is related to the amount of swelling of the prismatic secondary battery 100 that the spacer can absorb, and it can be said that the larger the value, the larger the amount of absorbed swelling. The constant load compression ratio of the elastic part 210 is preferably 40% or more. By setting the constant load compression ratio to a predetermined value or more, when the prismatic secondary battery 100 swells, the swelling can be efficiently absorbed over a long period.

[0039] In this specification, the "constant load compression ratio" refers to a value obtained as follows from the FS curve (horizontal axis: compression ratio, vertical axis: compression load) for which the elastic modulus was determined. That is, first, as shown in FIG. 5, the slope of the approximate straight line A for which the elastic modulus was determined is multiplied by 1.4 to obtain a straight line B. Next, the intersection point P between this straight line B and the FS curve is obtained. Then, a perpendicular line is dropped from this intersection point P to the horizontal axis, and the intersection point of the horizontal axis and the perpendicular line is defined as the constant load compression ratio. That is, the value of the horizontal axis at the intersection point P is defined as the constant load compression ratio. As shown in FIG. 5, the FS curve shows that the compression load increases quadratically as the compression ratio increases. That is, a large value of the constant compression load ratio means that the elastic modulus obtained from the range of compression ratios of 1 to 20% is less likely to change (rise) even on the higher compression ratio side. Therefore, by setting the constant load compression ratio to a predetermined value or more, the elastic modulus of the elastic part 210 is less likely to change, and when the prismatic secondary battery 100 swells, the swelling can be efficiently absorbed over a long period.

[0040] Considering the above-described ranges of elastic modulus and constant load compression ratio, the elastic part 210 is preferably made of a polymer material. Examples of the polymer material 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. Among them, EPDM and silicone rubber are preferred. The elastic part 210 is preferably made of rubber.

[0041] In addition, when the elastic part 210 is made of a thermoplastic resin such as polypropylene (PP) or polyethylene (PE), or when it is made of a metal such as aluminum, or a ceramic, glass, etc. as described in Patent Document 3, although it depends on its structure, etc., usually, it is considered that the above-described ranges of elastic modulus and / or constant load compression ratio are not satisfied. For example, the elastic modulus becomes much larger than 10 MPa, that is, it is considered that it is relatively difficult to elastically deform in the thickness direction X compared to the technology disclosed herein.

[0042] Figs. 6(A) and (B) are schematic views of the elastic part 210. Fig. 6(A) is a plan view of the rear surface 210Rr (the first Y-Z plane) orthogonal to the thickness direction X (the arrangement direction X), and Fig. 6(B) is a longitudinal sectional view taken along the line VIB-VIB of Fig. 6(A). As shown in Fig. 6(B), in the present embodiment, the elastic part 210 has a protrusion structure. The elastic part 210 includes a flat base part 216 and a plurality of protrusion parts 213 protruding from the base part 216 in the arrangement direction X. By forming the elastic part 210 into a protrusion structure, it becomes easier to satisfy the above-described ranges of elastic modulus and constant load compression ratio, and the elastic function can be stably exhibited even after charge and discharge cycles. The protrusion part 213 is an example of a protruding part extending in the arrangement direction X.

[0043] As can be seen from FIGS. 6(A) and 6(B), the base portion 216 extends along the front surface (the second Y-Z plane) of the elastic portion 210. The base portion 216 is a portion that does not have voids here. The base portion 216 is a non-porous (solid structure) portion. As shown in FIG. 6(B), the base portion 216 is provided on the surface (the front surface in FIG. 6(B)) on the side facing the heat insulating portion 220 here. However, in other embodiments, the base portion 216 may be provided on the surface on the side facing the long side wall 12b of the rectangular secondary battery 100. A plurality of protrusions 213 protrude from the base portion 216 along the thickness direction X (the arrangement direction X). By having the base portion 216, alignment with the heat insulating portion 220 becomes easy, and the productivity and workability in integrating the spacer 200 can be improved. The thickness (the length in the arrangement direction X) of the base portion 216 is preferably 0.1 mm or more, and 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.

[0044] The height (the length in the vertical direction Z) and / or the width (the length in the long side direction Y) of the base portion 216 preferably substantially coincide with the height and / or the width of the long side wall 12b of the rectangular secondary battery 100. Thereby, alignment with the rectangular secondary battery 100 becomes easy, and the productivity and workability of the assembled battery 500 can be improved.

[0045] The plurality of protrusions 213 are provided integrally with the base portion 216. The plurality of protrusions 213 have the same size, shape, etc. here. The protrusions 213 are regularly arranged in the Y-Z plane. In the Y-Z plane, a gap 211 is secured between the protrusions 213. The protrusions 213 extend from the base portion 216 toward the long side wall 12b of the rectangular secondary battery 100 here. The protrusions 213 have a frustum shape in outer shape here. As shown in FIG. 6(B), the cross-sectional shape of the protrusions 213 in the thickness direction X (the arrangement direction X) is preferably a trapezoidal shape. Thereby, it is possible to suppress the protrusions from falling down and the elastic function from deteriorating with the charge and discharge cycles. Note that the protrusions 213 are non-porous (solid structure) here, but may have a hollow (hollow) portion inside.

[0046] As shown in FIG. 6(B), the protrusion 213 has a contact region CA that directly contacts (abuts) the rectangular secondary battery 100 at the tip portion in the thickness direction X (array direction X). As shown in FIG. 6(A), the contact region CA of each protrusion 213 is circular in plan view here. Although not particularly limited, when the material of the elastic portion 210 is EPDM or silicone rubber, the area S of the contact region CA of one protrusion 213 is 1.5 mm 2 or more, more preferably 3 mm 2 or more. Also, the area S of the contact region CA of one protrusion 213 is preferably 100 mm 2 or less. The total area (total area) of the areas S of the plurality of protrusions 213 is 1.2 to 18 cm 2 per unit area (25 cm 2 ) of the elastic portion 210, preferably 1.5 to 15 cm 2 / 25 cm 2 is more preferably 1.5 to 15 cm 2 / 25 cm. By setting the area S to a predetermined value or more, a decrease in the elastic function can be suppressed. By setting the area S to a predetermined value or less, it becomes easier to adjust the elastic modulus and the constant load compression rate of the elastic portion 210 within the above ranges.

[0047] Although not particularly limited, when the material of the elastic portion 210 is rubber, such as EPDM or silicone rubber, the ratio (r / S) of the outer peripheral length r (mm) of the contact region CA to the area S (mm 2 ) of the contact region CA is preferably 0.6 or more and 2.7 or less. The above ratio (r / S) is more preferably 0.66 or more, further preferably 0.8 or more, and particularly preferably 0.9 or more. When the elastic portion 210 has a protrusion structure as in the present embodiment, it is more preferably 1.6 or more. By setting the above ratio to a predetermined value or more, it becomes easier to adjust the elastic modulus and the constant load compression rate of the elastic portion 210 within the above ranges. The above ratio (r / S) is more preferably 2.67 or less, further preferably 2.0 or less. By setting the above ratio to a predetermined value or less, the structure (here, the protrusion structure) of the elastic portion 210 can be stably maintained, and a decrease in the elastic function can be suppressed.

[0048] Note that the elastic modulus and the fixed load compression ratio of the elastic part 210 as described above can be adjusted, for example, by the material (type or hardness) of the elastic part 210 as described above, the number, size, shape, arrangement of the protrusions 213, the area S of the contact area CA, and the ratio (r / S) of the outer peripheral length r of the contact area CA to the area S of the contact area CA, etc.

[0049] The heat insulation part 220 is arranged between the elastic part 210 and the rectangular secondary battery 100 in the arrangement direction X. The heat insulation part 220 is a part with a lower thermal conductivity than the elastic part 210. In other words, the heat insulation part 220 is a part with higher heat insulation than the elastic part 210. By providing the heat insulation part 220, even if the rectangular secondary battery 100 generates heat during charging and discharging, etc., due to the heat insulation effect of the heat insulation part 220, the elastic part 210 is less likely to be affected by the heat generation. Therefore, the thermal degradation of the elastic part 210 can be suppressed. Also, even if the temperature of the rectangular secondary battery 100 rises, it can be suppressed that the heat is transmitted to the adjacent rectangular secondary battery 100. Therefore, the chain heat generation of the rectangular secondary batteries 100 can be suppressed, and it is possible to prevent the entire assembled battery 500 from becoming excessively high temperature.

[0050] From such a viewpoint, the thermal conductivity of the heat insulation part 220 is preferably 0.15 W / (m·K) or less, and more preferably 0.1 W / (m·K) or less. Also, it is more preferable that the heat insulation part 220 is arranged on both surfaces in the arrangement direction X of the elastic part 210. Thereby, the effects of the technology disclosed herein can be exhibited at a particularly high level. Note that in this specification, the thermal conductivity refers to a value measured based on JIS A1412-1 (2016).

[0051] The heat insulation part 220 may be a porous body. Thereby, air is included in the heat insulation part 220, and a high heat insulation function can be exhibited. The heat insulation part 220 is preferably configured to include, for example, an inorganic filler (such as ceramics such as alumina) and a polymer material. The heat insulation part 220 is preferably configured with the inorganic filler as the main component (the component that occupies the largest mass among the constituent components, for example, the component that occupies 50 mass% or more when the entire constituent components are 100 mass%).

[0052] In a preferred embodiment, for example, when the spacer 200 is assembled to and compressed by the assembled battery 500, a part of the elastic portion 210 is disposed within the heat insulating portion 220. In one example, the elastic portion 210 has one or more convex portions, the heat insulating portion 220 has concave portions corresponding to such convex portions, and the convex portions of the elastic portion 210 are disposed within the concave portions of the heat insulating portion 220. More specifically, for example, a part of the protruding portion 213 of the elastic portion 210 (the portion near the heat insulating portion 220) bites into the heat insulating portion 220. Alternatively, in another example, conversely to the above, the heat insulating portion 220 has one or more convex portions, the elastic portion 210 has concave portions corresponding to such convex portions, and the convex portions of the heat insulating portion 220 are disposed within the concave portions of the elastic portion 210. More specifically, for example, the convex portion of the heat insulating portion 220 pierces between the protruding portions 213 of the elastic portion 210 (the portion of the gap 211). Thereby, the integrality between the elastic portion 210 and the heat insulating portion 220 can be improved, and the lamination deviation can be prevented. Further, since the elastic portion 210 and the heat insulating portion 220 partially overlap in the thickness direction X, the spacer 200 can be made thinner, and the volume energy density of the assembled battery 500 can be improved.

[0053] The assembled battery 500 can be used for various applications. In particular, since the rectangular secondary battery 100 is likely to expand with charge and discharge cycles, it can be suitably used as a power source (driving power source) for a motor mounted on a vehicle that requires high capacity, such as a passenger car, a truck, etc. The type of the 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).

[0054] <Second Embodiment> Figs. 7(A) and 7(B) are schematic views of the elastic part 210a. Fig. 7(A) is a plan view of a plane (the first Y-Z plane) orthogonal to the thickness direction X (arrangement direction X), and Fig. 7(B) is a longitudinal sectional view taken along line VIIB-VIIB of Fig. 7(A). The second embodiment is the same as the above-described first embodiment except that the spacer includes the elastic part 210a instead of the elastic part 210. The elastic part 210a has a flat plate shape on the outer shape, similar to the elastic part 210 of the first embodiment. As shown in Fig. 7(A), the elastic part 210a of the present embodiment has a pore structure. By making the elastic part 210a have a pore structure, it becomes easier to satisfy the ranges of the elastic modulus and the fixed load compression ratio as described above, and the elastic function can be stably exhibited even after the charge-discharge cycle. Further, since the plurality of hollow parts 212 extend along the thickness direction X (arrangement direction X), for example, compared with the case where the plurality of hollow parts 212 extend perpendicular to the arrangement direction X, the structure can be relatively stably maintained, and a decrease in the elastic function can be suppressed.

[0055] The elastic part 210a includes a partition wall (rib) 214 extending along the thickness direction X (arrangement direction X) and a plurality of hollow parts 212 partitioned by the partition wall 214 and regularly arranged in the thickness direction X (arrangement direction X). Here, the elastic part 210a further includes a base part 216a. The properties of the base part 216a may be the same as those of the base part 216 of the first embodiment. However, the base part 216a is not essential and can be omitted in other embodiments. The partition wall 214 is an example of a protruding part extending in the arrangement direction X.

[0056] The partition wall 214 constitutes the framework of the elastic part 210a. As shown in Fig. 7(A), the partition wall 214 is regularly provided on the rear surface (the first Y-Z plane). The partition wall 214 extends along the thickness direction X (from the front side to the back side in Fig. 7(A)). The partition wall 214 partitions the plurality of hollow parts 212.

[0057] The plurality of hollow portions 212 are partitioned by partition walls 214 and are regularly arranged along the thickness direction X (array direction X). The plurality of hollow portions 212 are independent of each other here. These points are different from a porous (sponge-like) structure having voids communicating in a three-dimensional network form. Although not particularly limited, the size (volume) of one hollow portion 212 is 1 mm 3 or more. The shape of the hollow portion 212 in the Y-Z plane view is hexagonal here. That is, the hollow portion 212 has a hexagonal prism shape here along the thickness direction X.

[0058] Figure 7 (B) As shown, one end (the front end in Figure 7 (B)) of the hollow portion 212 in the thickness direction X (array direction X) is closed here. Here, the surface of the hollow portion 212 on the side facing the heat insulating portion 220 is closed by the base portion 216a. The thickness (length in the array direction X) of the base portion 216a does not have to be uniform in the Y-Z plane, and there may be partially thick or thin portions. Also, the area of the base portion 216a in the Y-Z plane may be equal to or larger than the area in the Y-Z plane where the partition wall 214 exists.

[0059] The elastic portion 210a is comb-shaped in a cross-sectional view in the thickness direction X. By closing one end of the hollow portion 212 in this way, integration with the heat insulating portion 220 becomes easy and workability can be improved. On the other hand, as shown in Figure 7 (A), the other end (the rear end) of the hollow portion 212 in the thickness direction X (array direction X) is open. Here, the surface of the hollow portion 212 on the side facing the long side wall 12b of the rectangular secondary battery 100 is open. The elastic portion 210a has a non-through hole structure. However, regardless of whether the base portion 216a is included or not, the hollow portion 212 may be a through hole with both ends in the thickness direction X (array direction X) being 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 "hole structure" refers to the entire structure having a plurality of hollow portions 212 regularly arranged along the thickness direction X (array direction X).

[0060] The elastic part 210a has a honeycomb structure here. As a result, it becomes easier to maintain the hollow part 212 even when the charge-discharge cycle is repeated, and the elastic function can be stably exhibited even after the charge-discharge cycle. In this specification, the "honeycomb structure" is a structure included in the "hole structure", and is not limited to the case where the shape of the hollow part 212 in the Y-Z plane view is hexagonal, and generally refers to the three-dimensional space filling in which solid figures are arranged without gaps.

[0061] In the plane (Y-Z plane) orthogonal to the thickness direction X (array direction X), the ratio of the total area of the plurality of hollow parts 212 to the total area of the elastic part 210a is preferably 0.25 or more, and more preferably 0.35 to 0.8. By setting the above ratio to a predetermined value or more, when the prismatic secondary battery 100 expands, it is likely to collapse and is likely to absorb the expansion. By setting the above ratio to a predetermined value or less, the hollow part 212 can be stably maintained, and the durability of the elastic part 210 can be improved.

[0062] In this embodiment, the ratio (r / S) of the outer peripheral length r of the contact area to the area S of the contact area described above can be obtained as the ratio (r / S) of the total outer peripheral length r (mm) of the contact area CA of the entire partition wall 214 to the total area S (mm 2 ) of the entire contact area of the partition wall 214. Also, the "sum (total area) of the areas S of the plurality of protrusions 213" can be read as the "total area S of the entire contact area of the partition wall 214".

[0063] Hereinafter, several examples related to the present invention will be described, but the present invention is not intended to be limited to such examples.

[0064] <Fabrication of a battery pack> First, a plurality of lithium-ion secondary batteries were prepared. Next, spacers (Examples 1 to 7, Comparative Examples 1 to 4) including elastic portions were prepared. The thickness of the elastic portion was set to 0.075 times the thickness of the lithium-ion secondary battery (7.5% of the thickness of the lithium-ion secondary battery) when the thickness of the lithium-ion secondary battery was taken as 1. The elastic portions of the spacers (Examples 1 to 7, Comparative Examples 1 to 4) each have an elastic modulus and a constant load compression ratio shown in Table 1.

[0065] The elastic portion of each spacer is made of the material shown in Table 1 and has the shape shown in Table 1. For example, the spacers of Examples 1, 3, 4, 5, 6 and Comparative Examples 1, 2 are made of EPDM and have a protrusion structure including a flat and non-porous (solid structure) base portion and a plurality of protrusions extending in the thickness direction from the base portion. The spacer of Example 2 is made of silicone rubber and has a honeycomb structure including a partition wall extending along the thickness direction and a plurality of hollow portions partitioned by the partition wall and regularly arranged in the thickness direction. The spacer of Example 7 is made of foamed silicone and is a porous sheet having (irregular) voids communicating in a three-dimensional network. The spacers of Comparative Examples 3, 4 are made of foamed urethane and are a porous sheet having (irregular) voids communicating in a three-dimensional network.

[0066] <Calculation of the ratio (r / S)> FIG. 8 is a plan view schematically showing one protrusion of the spacer in Example 1. In Example 1, the contact area of the protrusion is square in plan view. In Examples 1, 3, 4, 5, 6 and Comparative Examples 1, 2 having a protrusion structure, as shown in FIG. 8, the ratio (r / S) of the outer peripheral length r (mm) of the contact area of one protrusion to the area S (mm 2 ) of the contact area of one protrusion was calculated. In Example 2 having a honeycomb structure, the ratio (r / S) of the total outer peripheral length r (mm) of the contact area of the entire partition wall to the total area S (mm 2 ) of the contact area of the entire partition wall was calculated. The results are shown in Table 1.

[0067] <Fabrication of the battery pack 2> Next, the lithium-ion secondary battery and the spacer were sandwiched in the arrangement direction by a pair of restraining jigs, and were restrained so that the thickness of the spacer became 80% of that before restraint, thereby fabricating a test battery. Then, the distance (initial thickness) between the pair of restraining jigs was measured.

[0068] <Cycle test> In a temperature environment of 40 °C, the SOC (State of Charge) of the secondary battery was adjusted to 15%, and after constant current constant voltage charging to SOC 95% at a charging rate of 0.2C, a rest was taken for 5 minutes, and then after constant current constant voltage discharging to SOC 15% at a discharging rate of 0.5C, charging and discharging with a 90-minute rest was defined as one cycle, and this was repeated 200 cycles.

[0069] <Evaluation of the change in the thickness 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.

[0070] <Judgment on the occurrence of Li deposition> After the cycle test, the lithium-ion secondary battery was disassembled, and the occurrence of Li deposition on the negative electrode and the separator of the electrode body was visually confirmed. The results are shown in Table 1.

[0071]

Table 1

[0072] As shown in Table 1, in Comparative Examples 1 to 3, the thickness after cycle was relatively large. As a reason for this, in Comparative Examples 1 and 2, it is considered that the swelling of the secondary battery could not be fully absorbed because the constant load compression rate of the elastic part of the spacer was less than 35%. Further, in Comparative Example 3, it is considered that the elastic modulus of the elastic part of the spacer was low and the swelling of the secondary battery could not be suppressed.

[0073] Also, as shown in Table 1, in Comparative Examples 3 and 4, Li deposition was observed after the cycle test. The reason for this is considered to be that since the elastic modulus of the elastic part of the spacer was less than 1 MPa, the load applied to the secondary battery was insufficient, the inter-pole distance between the positive and negative electrodes increased, and the charge and discharge reactions became non-uniform.

[0074] In contrast to these comparative examples, in Examples 1 to 7, the thickness after cycling was relatively small, and no Li deposition was observed. The reason for this is considered to be that by making the elastic part satisfy a predetermined elastic modulus, the swelling of the secondary battery after the charge and discharge cycle can be preferably suppressed or absorbed, and by making the constant load compression rate be a value equal to or greater than a predetermined value, such an effect can be maintained longer (in the direction of increasing the number of cycles). These results indicate the significance of the technology disclosed herein.

[0075] As described above, the preferred embodiments of the present invention have been explained, but the above embodiments are merely examples. The present invention can be implemented in various other forms. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the art. The technology described in the claims includes various modifications and changes of the above-exemplified embodiments. For example, it is also possible to replace a part of the above-described embodiments with the following modification examples, and it is also possible to add other modification examples to the above-described embodiments. Also, if the technical features are not described as essential, they can be appropriately deleted.

[0076] (1) For example, in the above-described first to second embodiments, the elastic part 210 and the heat insulating part 220 each had a flat outer shape, and the areas of the surfaces (Y-Z planes) orthogonal to the thickness direction X (arrangement direction X) were substantially the same. However, this is not limiting. The areas of the elastic part 210 and the heat insulating part 220 in the Y-Z plane may be different from each other. In a modified example, it is preferable that the area of the Y-Z plane of the elastic part 210 is less than or equal to the area of the Y-Z plane of the heat insulating part 220. When the area of the heat insulating part 220 is large, the influence of the heat generation of the rectangular secondary battery 100 can be further reduced, and the thermal degradation of the elastic part 210 can be suppressed at a high level.

[0077] (2) For example, in the above-described first embodiment, the elastic part 210 had a protrusion structure. The plurality of protrusion parts 213 had a truncated cone shape in outer shape, and the contact area CA of each protrusion part 213 was circular in plan view. However, this is not limiting. The outer shape of the protrusion part 213 may be cylindrical, polygonal columnar (triangular columnar, square columnar, etc.), or the like. The contact area CA may be circular, polygonal (triangular, square, etc.), or the like in plan view.

[0078] (3) For example, in the above-described second embodiment, the plurality of hollow parts 212 of the elastic part 210a were independent of each other. However, this is not limiting. The plurality of hollow parts 212 may be communicated by hole parts penetrating the partition wall 214. In other words, the elastic part 210a may have hole parts communicating the plurality of hollow parts 212. According to such an aspect, the entry and exit of air in the plurality of hollow parts 212 become smooth, and a decrease in the elastic function due to the so-called suction cup effect can be suppressed.

[0079] (4) For example, in the above-described second embodiment, the elastic part 210a has a honeycomb structure, and the elastic part 210 aThe plurality of hollow portions 212 contained therein had a hexagonal shape when viewed in the Y-Z plane. However, it is not limited to this. The hollow portion 212 may not have a honeycomb structure. The hollow portions 212 may be randomly arranged. Further, the shape of the hollow portion 212 when viewed in the Y-Z plane may be a shape other than a hexagonal shape, for example, a circular shape, a triangular shape, a quadrangular shape, etc. Also, the hollow portion 212 may be partitioned in the middle of the space in the thickness direction X (array direction X).

[0080] As described above, specific aspects of the technology disclosed herein include those described in the following respective paragraphs. Paragraph 1: A battery pack including a plurality of rectangular secondary batteries arranged along a predetermined array direction and a spacer arranged between the adjacent rectangular secondary batteries in the array direction, wherein the spacer includes an elastic portion, and the elastic portion satisfies the following conditions: (1) The elastic modulus obtained as the slope of the approximate straight line A in the range of a compression ratio of 1% to 20% from the compression load-compression ratio curve (horizontal axis: compression ratio, vertical axis: compression load) created by compressing at a compression speed of 12 kPa / min until the compression load in the array direction reaches 3.9 MPa is 1 MPa or more and 10 MPa or less; (2) The constant load compression ratio obtained as the value of the horizontal axis at the intersection of the compression load-compression ratio curve and a straight line B whose slope is 1.4 times the slope of the approximate straight line A is 35% or more and 70% or less. A battery pack that satisfies both conditions. Paragraph 2: The battery pack according to Paragraph 1, wherein the elastic portion has a protruding portion extending in the array direction, the protruding portion has a contact area that contacts the rectangular secondary battery, and the ratio (r / S) of the outer peripheral length r (mm) of the contact area to the area S (mm 2 ) of the contact area is 0.6 or more and 2.7 or less. Paragraph 3: The battery pack according to Paragraph 1 or Paragraph 2, wherein the elastic portion has a honeycomb structure and includes partition walls extending along the array direction and a plurality of hollow portions partitioned by the partition walls and regularly arranged in the array direction. Paragraph 4: The battery pack according to Paragraph 1 or Paragraph 2, wherein the elastic portion has a protruding structure and includes a flat base portion and a plurality of protruding portions protruding from the base portion in the array direction. Item 5: The assembled battery according to any one of Items 1 to 4, wherein the spacer is disposed between the elastic part and the rectangular secondary battery in the array direction, and further includes a heat insulating part having a lower thermal conductivity than the elastic part. Item 6: The assembled battery according to any one of Items 1 to 5, wherein the elastic modulus of the elastic part is 1 MPa or more and 3.3 MPa or less.

Explanation of Reference Numerals

[0081] 10 Battery case 20 Electrode body 100 Rectangular secondary battery 200 Spacer 210, 210a Elastic part 212 Hollow part 213 Protrusion (projecting part) 214 Partition wall (projecting part) 216, 216a Base part 220 Heat insulating part 300 Restraining mechanism 500 Assembled battery

Claims

1. A battery pack comprising: a plurality of rectangular secondary batteries arranged along a predetermined arrangement direction; a spacer disposed between the adjacent rectangular secondary batteries in the arrangement direction; wherein the spacer includes an elastic portion made of rubber-like materials; the elastic portion has a honeycomb structure and includes partition walls extending along the arrangement direction and a plurality of hollow portions defined by the partition walls and regularly arranged in the arrangement direction; the partition walls form protrusions extending in the arrangement direction; the protrusions have contact regions that contact the rectangular secondary batteries; a ratio (r / S) of an outer peripheral length r (mm) of the contact region to an area S (mm2) of the contact region is 0.6 or more and 2.7 or less; and the elastic portion satisfies the following conditions: (1) An elastic modulus obtained as a slope of an approximate straight line A in a range of a compression ratio of 1% to 20% from a compression load-compression ratio curve (horizontal axis: compression ratio, vertical axis: compression load) created by compressing at a compression speed of 12 kPa / min until a compression load becomes 3.9 MPa in the arrangement direction is 1 MPa or more and 10 MPa or less; (2) A fixed load compression ratio obtained as a value of the horizontal axis at an intersection of the compression load-compression ratio curve and a straight line B having a slope 1.4 times that of the approximate straight line A is 35% or more and 70% or less. The battery pack satisfying both of the above conditions.

2. The elastic portion is made of silicone rubber. The battery pack according to claim 1.

3. A battery pack comprising: a plurality of rectangular secondary batteries arranged along a predetermined arrangement direction; a spacer disposed between the adjacent rectangular secondary batteries in the arrangement direction; wherein the spacer includes an elastic portion made of rubber-like materials; the elastic portion has a protrusion structure and includes a flat base portion and a plurality of protrusion portions protruding from the base portion in the arrangement direction; the protrusion portions form protrusions extending in the arrangement direction; the protrusions have contact regions that contact the rectangular secondary batteries; a ratio (r / S) of an outer peripheral length r (mm) of the contact region to an area S (mm2) of the contact region is 0.6 or more and 2.7 or less; and the elastic portion satisfies the following conditions: (1) An elastic modulus obtained as a slope of an approximate straight line A in a range of a compression ratio of 1% to 20% from a compression load-compression ratio curve (horizontal axis: compression ratio, vertical axis: compression load) created by compressing at a compression speed of 12 kPa / min until a compression load becomes 3.9 MPa in the arrangement direction is 1 MPa or more and 10 MPa or less; ​ ​ The constant load compression rate obtained as the value of the horizontal axis at the intersection of the compression load-compression rate curve and a straight line B whose slope is 1.4 times that of the approximate straight line A is 35% or more and 70% or less; A battery pack that satisfies all of them.

4. The elastic part is made of ethylene propylene rubber, The battery pack according to claim 3.

5. The spacer is disposed between the elastic part and the rectangular secondary battery in the arrangement direction, and further includes a heat insulating part having a lower thermal conductivity than the elastic part. The battery pack according to any one of claims 1 to 4.

6. The elastic modulus of the elastic part is 1 MPa or more and 3.3 MPa or less. The battery pack according to any one of claims 1 to 4.

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