Battery pack and manufacturing method thereof

Abstract

To provide a battery pack of which variation of a reaction acting on a battery cell is small, and provide a manufacturing method of the same.SOLUTION: A battery pack comprises: a plurality of battery cells arranged in a first direction; a separator between the plurality of battery cells; and a binding member binding the plurality of battery cells and the separator along the first direction. The separator includes: a base part; a first member that includes a plurality of convex parts projected in a first direction from the base part; and a second member located between the plurality of convex parts, relatively high in adiathermancy against the first member, and relatively deformable in the first member.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present technology relates to a battery pack and a manufacturing method thereof. [Background technology]

[0002] Chinese Utility Model No. 215119123 (Patent Document 1) discloses a separator structure arranged between multiple battery cells, in which a heat insulating material and an elastic body are layered. Japanese Patent Application Laid-Open No. 2021-150079 (Patent Document 2) discloses an elastic body in which a hard portion protrudes from a through-hole in a soft portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Chinese Utility Model No. 215119123 [Patent Document 2] Japanese Patent Publication No. 2021-150079 Summary of the Invention [Problem to be solved by the invention]

[0004] The separator described in Patent Document 1 has a two-layer structure of an insulating material and an elastomer, so the thickness tolerance of the separator is the sum of the thickness tolerance of the insulating material and the thickness tolerance of the elastomer.

[0005] Therefore, the separator thickness tolerance tends to be larger compared to separators made of a single component. Even if the design value of the dimension in the stacking direction of the battery cells is the same, if the separator thickness is large, the restraining load of the battery cells will be large. As the maximum restraining load of the battery cells increases, it becomes necessary to improve the strength of the reinforcing members in the battery module, which can lead to an increase in the weight and cost of the battery module.

[0006] Furthermore, in the elastic body described in Patent Document 2, when the elastic body is incorporated into a secondary battery module, the soft parts are usually separated from the electrode body, and it is assumed that the hard parts scattered throughout the elastic body become easily deformed, thereby bearing the load from the electrode body.

[0007] An object of the present technology is to provide a battery pack with small variations in reaction forces acting on battery cells, and a method for manufacturing the same. [Means for solving the problem]

[0008] The present technology provides the following assembled battery and manufacturing method thereof.

[0009] [1] A battery pack comprising: a plurality of battery cells arranged in a first direction; separators between the plurality of battery cells; and a restraining member that restrains the plurality of battery cells and separators along the first direction, wherein the separator includes a first member including a base portion and a plurality of protrusions protruding from the base portion in the first direction; and a second member that is between the plurality of protrusions, has relatively high thermal insulation properties compared to the first member, and is relatively more deformable compared to the first member.

[0010] [2] The battery pack according to [1], wherein when the separator is removed from the battery pack, the protruding height of the plurality of protrusions is greater than the thickness of the second member.

[0011] [3] The battery pack according to [1] or [2], wherein the first member and the second member have substantially the same outer dimensions.

[0012] [4] The battery pack according to any one of [1] to [3], wherein the base portion of the first member and the plurality of protrusions are integrally formed.

[0013] [5] The battery pack according to any one of [1] to [4], wherein the second member is made of a foamed resin.

[0014] [6] A method for manufacturing a battery pack, comprising the steps of: preparing a plurality of battery cells and separators; arranging the plurality of battery cells and separators alternately in a first direction; and restraining the plurality of battery cells and separators along the first direction, wherein the step of preparing the separator includes preparing a first member including a base portion and a plurality of protrusions protruding from the base portion in the first direction; and providing a second member between the plurality of protrusions, the second member having relatively high thermal insulation properties compared to the first member and being relatively more deformable compared to the first member, and wherein preparing the first member includes making the protruding height of the plurality of protrusions greater than the thickness of the second member.

[0015] [7] The method for manufacturing a battery pack according to [6], wherein the step of preparing a separator includes foaming a resin within a recess surrounded by a series of convex portions of the first member, thereby disposing a second member made of a foamed resin between the plurality of convex portions of the first member. [Effects of the Invention]

[0016] According to the present technology, it is possible to provide a battery pack with small variations in reaction forces acting on battery cells, and a method for manufacturing the same. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. [Figure 2] FIG. [Figure 3] FIG. 2 is a perspective view of a battery module. [Figure 4] FIG. 2 is a cross-sectional view of a separator included in the battery pack. [Figure 5] FIG. 5 is a diagram showing the separator shown in FIG. 4 placed between battery cells. [Figure 6] FIG. 2 is a top view of a first member of the separator. [Figure 7] FIG. 4 is a top view of a second member of the separator. [Figure 8] FIG. 10 is a cross-sectional view of a separator according to a comparative example. [Figure 9]FIG. 9 is a diagram showing the separator shown in FIG. 8 placed between battery cells. [Figure 10] FIG. 10 is a top view of a separator according to a modified example. [Figure 11] 11 is a cross-sectional view taken along the line XI-XI in FIG. [Figure 12] FIG. 4 is a diagram showing deformation when a load is applied to a first member of the separator. [Figure 13] FIG. 10 is a diagram showing deformation when a load is applied to the second member of the separator. [Figure 14] 4 is a graph showing an example of load-thickness curves of a first member and a second member in a separator. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present technology will be described. Note that the same or corresponding parts are denoted by the same reference characters, and description thereof may not be repeated.

[0019] In the embodiments described below, when numbers, amounts, etc. are mentioned, the scope of the present technology is not necessarily limited to those numbers, amounts, etc., unless otherwise specified. Furthermore, in the following embodiments, each component is not necessarily essential to the present technology, unless otherwise specified. Furthermore, the present technology is not necessarily limited to those that achieve all of the effects and advantages mentioned in the present embodiments.

[0020] In this specification, the terms "comprise," "include," and "have" are open-ended. That is, when a certain feature is included, other features may or may not be included.

[0021] Furthermore, when geometric terms and terms expressing positional and directional relationships are used in this specification, such as "parallel," "orthogonal," "45° diagonal," "coaxial," and "along," these terms allow for manufacturing errors and slight variations. When terms expressing relative positional relationships, such as "upper side" and "lower side," are used in this specification, these terms are used to indicate relative positional relationships in a single state, and the relative positional relationships can be reversed or rotated to any angle depending on the installation direction of each mechanism (for example, by turning the entire mechanism upside down).

[0022] In this specification, "battery" is not limited to lithium-ion batteries, but may include other batteries such as nickel-metal hydride batteries and sodium-ion batteries.

[0023] In this specification, "battery cells" are not necessarily limited to rectangular ones, but may also include cells of other shapes, such as cylindrical, pouch, and blade types. Furthermore, "battery cells" can be installed in hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs). However, the use of "battery cells" is not limited to in-vehicle use.

[0024] Fig. 1 is a perspective view of a battery pack 1A. The battery pack 1A shown in Fig. 1 includes battery cells 100 and separators 200 (inter-cell separators). The battery cells 100 and the separators 200 are arranged alternately along the Y-axis direction (first direction).

[0025] The battery cells 100 are rectangular battery cells, and a plurality of battery cells 100 are provided along the Y-axis direction. The plurality of battery cells 100 are electrically connected to one another via bus bars (not shown).

[0026] The separators 200 are provided between the multiple battery cells 100. The separators 200 prevent unintended electrical conduction between adjacent battery cells 100. The separators 200 ensure electrical insulation between adjacent battery cells 100.

[0027] 2 is a perspective view of the battery cell 100. As shown in Fig. 2, the battery cell 100 has a rectangular shape. The battery cell 100 has an electrode terminal 110, a battery case 120, and a gas release valve 130.

[0028] The electrode terminal 110 is formed on the battery case 120. The electrode terminal 110 has a positive electrode terminal 111 and a negative electrode terminal 112 that are aligned along an X-axis direction (second direction) that is perpendicular to a Y-axis direction (first direction). The positive electrode terminal 111 and the negative electrode terminal 112 are spaced apart from each other in the X-axis direction.

[0029] The battery case 120 has a rectangular parallelepiped shape and forms the exterior of the battery cell 100. The battery case 120 includes a case body 120A that houses an electrode assembly and an electrolyte (not shown), and a sealing plate 120B that seals the opening of the case body 120A. The sealing plate 120B is joined to the case body 120A by welding.

[0030] The battery case 120 has an upper surface 121, a lower surface 122, a first side surface 123, a second side surface 124, and two third side surfaces 125.

[0031] The upper surface 121 is a plane perpendicular to the Z-axis direction (third direction) that is perpendicular to the Y-axis direction and the X-axis direction. The electrode terminals 110 are disposed on the upper surface 121. The lower surface 122 faces the upper surface 121 along the Z-axis direction.

[0032] Each of the first side surface 123 and the second side surface 124 is a plane perpendicular to the Y-axis direction. Each of the first side surface 123 and the second side surface 124 has the largest area among the multiple side surfaces of the battery case 120. Each of the first side surface 123 and the second side surface 124 has a rectangular shape when viewed in the Y-axis direction. Each of the first side surface 123 and the second side surface 124 has a rectangular shape when viewed in the Y-axis direction, with the X-axis direction being the longitudinal direction and the Z-axis direction being the lateral direction.

[0033] The multiple battery cells 100 are stacked such that the first side surfaces 123 and the second side surfaces 124 of the battery cells 100 adjacent to each other in the Y-axis direction face each other. As a result, the positive electrode terminals 111 and the negative electrode terminals 112 are arranged alternately in the Y-axis direction in which the multiple battery cells 100 are stacked.

[0034] The gas release valve 130 is provided on the top surface 121. When the temperature of the battery cell 100 rises (thermal runaway) and the internal pressure of the battery case 120 exceeds a predetermined value due to gas generated inside the battery case 120, the gas release valve 130 releases the gas to the outside of the battery case 120.

[0035] 3 is a perspective view of the battery module 1. As shown in FIG. 3, the battery module 1 includes battery cells 100, separators 200, binding members 300, and end plates 400.

[0036] The battery cells 100 and separators 200 arranged alternately along the Y-axis direction (first direction) are pressed by the end plates 400 and are constrained between the two end plates 400.

[0037] The end plates 400 are arranged at both ends in the Y-axis direction. The end plates 400 are fixed to a base such as a case that houses the battery module 1. The restraining member 300 connects the two end plates 400 to each other and restrains the multiple battery cells 100 and separators 200 along the Y-axis direction.

[0038] The restraining members 300 are fixed to the end plates 400 while a compressive force in the Y-axis direction is applied to the stack of battery cells 100, separators 200, and end plates 400, and the compressive force is then released, causing a tensile force to act on the restraining members 300 connecting the two end plates 400. In reaction to this, the restraining members 300 press the two end plates 400 in a direction that brings them closer together. This completes the construction of the battery module 1.

[0039] A battery pack is formed by storing the battery module 1 in a pack case (cell-module-pack structure). Alternatively, the battery pack 1A shown in Fig. 1 may be directly supported by the wall of the pack case (cell-to-pack structure).

[0040] Fig. 4 is a cross-sectional view of the separator 200. Fig. 5 is a diagram showing the separator 200 shown in Fig. 4 placed between battery cells 100. Fig. 6 is a top view of the first member 210, and Fig. 7 is a top view of the second member 220.

[0041] 4 to 7, the separator 200 includes a first member 210 and a second member 220. The first member 210 and the second member 220 are stacked in the stacking direction of the multiple battery cells 100 (the Y-axis direction).

[0042] The first member 210 includes a base portion 211 and a plurality of protrusions 212 protruding from the base portion 211 in the Y-axis direction. The protrusions 212 have a tapered shape that decreases in diameter toward the tip. In the example of Fig. 4, the base portion 211 and the plurality of protrusions 212 are integrally molded, but the base portion 211 and the protrusions 212 may be provided as separate bodies and joined together.

[0043] The second member 220 has holes 221. The protrusions 212 of the first member 210 are inserted into the holes 221 of the second member 220. As a result, the second member 220 is positioned between the multiple protrusions 212. As an example, the outer dimensions of the first member 210 and the second member 220 are approximately equal to each other.

[0044] Typically, as shown in FIG. 4, when the separator 200 is removed from the battery pack 1A, the protruding height of the multiple protrusions 212 is greater than the thickness of the second member 220. However, the scope of the present technology is not limited to this. After preparing the separator 200 shown in FIG. 4, the multiple battery cells 100 and the separator 200 are alternately arranged in the Y-axis direction and are further constrained along the Y-axis direction. At this time, as shown in FIG. 5, the protrusions 212 of the first member 210 are compressed together with the second member 220.

[0045] The first member 210 may be made of an elastic material such as silicone rubber, fluororubber, urethane rubber, natural rubber, styrene butadiene rubber, butyl rubber, ethylene propylene rubber (EPM, EPDM), butadiene rubber, isoprene rubber, or norbornene rubber (preferably silicone rubber or fluororubber).

[0046] The first member 210 is preferably made of a material having an elastic modulus of about 1 MPa to 10 MPa, as measured by the following method. [Method for measuring elastic modulus] (1) Prepare a square test piece with a side length of 5 cm (the surface facing the battery cell). (2) For the above test piece, a load-displacement curve (FS curve) is obtained up to a pressure of 3.9 MPa (pressure rate: 30 N / min). (3) In a graph with the horizontal axis representing the compression rate and the vertical axis representing the pressure, the elastic modulus is calculated from the slope of the compression rate from 1% to 20%.

[0047] Furthermore, it is preferable to construct the first member 210 using a material that allows the sample to rest for 2 hours after the pressure test (after unloading), and the thickness of the sample measured with a micrometer is approximately -20% or less of the initial state (before the pressure test).

[0048] The second member 220 has relatively high heat insulating properties compared to the first member 210, and is relatively more deformable compared to the first member 210.

[0049] The second member 220 may be made of foamed resin. The second member 220 may be made of, for example, inorganic fibers (ceramic fibers, etc.), inorganic fibers and organic binder molding, inorganic filler and organic binder, or a foamed silicone sheet with an internal space.

[0050] The second member 220 preferably has a thermal insulation property of about 0.15 W / mK or less, and more preferably has a thermal insulation property of about 0.1 W / mK or less.

[0051] As shown in Figures 4 to 7, by using a separator 200 having a two-layer structure consisting of a first member 210 with a relatively high elastic modulus and a second member 220 with a relatively high thermal insulation property, it is possible to achieve both deformation absorption and thermal insulation properties in the separator 200.

[0052] Fig. 8 is a cross-sectional view of a separator 200A according to a comparative example, and Fig. 9 is a diagram showing the separator 200A shown in Fig. 8 arranged between battery cells 100.

[0053] The separator 200A shown in FIGS. 8 and 9 has a two-layer structure in which a first member 210A having a relatively high elastic modulus and a second member 220A having a relatively high thermal insulation property are stacked.

[0054] Separator 200A has a two-layer structure of first member 210A and second member 220A, so the thickness tolerance of separator 200A is the sum of the thickness tolerance of first member 210A and the thickness tolerance of second member 220A.

[0055] In this way, the thickness tolerances of the two components are added together, resulting in a larger thickness tolerance for the separator compared to a separator made of a single component. As a result, even if the design values of the dimensions in the stacking direction (Y-axis direction) of the battery cells 100 are the same, the binding load on the battery cells 100 and separator 200A increases depending on the thickness of the separator 200A. This creates a need to improve the strength of the reinforcing members in the battery pack 1A or battery module 1, which can lead to increased weight and cost for the battery module 1.

[0056] In contrast, the separator 200 according to this embodiment is structured so that the second member 220 is provided between the protrusions 212 of the first member 210. This means that it is only necessary to control the dimensional tolerance of the first member 210, and this reduces the overall variation in thickness of the separator 200. As a result, a battery module 1 is provided that has small variations in the reaction force acting on the battery cells 100, which can contribute to reducing the weight and manufacturing costs of the battery module.

[0057] Fig. 10 is a top view of a separator 200 according to a modified example, and Fig. 11 is a cross-sectional view taken along line XI-XI in Fig. 10 .

[0058] 10 and 11, a foam having an air layer therein is used as the second member 220. When preparing this separator 200, resin is foamed in the recesses 213 surrounded by the continuous protrusions 212 of the first member 210. As a result, the second member 220 made of foamed resin is formed between the multiple protrusions 212 of the first member 210.

[0059] Next, the relationship between the modulus of elasticity of the first member 210 and the modulus of elasticity of the second member 220 will be described with reference to FIGS.

[0060] Fig. 12 is a diagram showing deformation when a load is applied to the first member 210 of the separator 200. Fig. 13 is a diagram showing deformation when a load is applied to the second member 220 of the separator 200.

[0061] As shown in FIG. 12, when a load F1 is applied to the first member 210 having a thickness T when no load is applied, the protrusions 212 are mainly compressed and deformed, and the thickness of the first member 210 decreases to T'.

[0062] As shown in FIG. 13, when a load F2 is applied to the second member 220, which has a thickness S when no load is applied, the second member 220 undergoes compressive deformation, and the thickness of the second member 220 decreases to S'.

[0063] Fig. 14 is a graph showing an example of a load-thickness curve of the first member 210 and the second member 220 of the separator 200. In Fig. 14, curve 10 is an example of a load-thickness curve of the first member 210 of the separator 200, and curves 20A and 20B are each an example of a load-thickness curve of the second member 220 of the separator 200. The vertical axis of Fig. 14 represents the load acting on the first member 210 and the second member of the separator 200, and the horizontal axis represents the thickness of the separator 200 (first member 210).

[0064] As shown by curves 10, 20A, and 20B in FIG. 14, the loads acting on the first member 210 and the second member 220 in the separator 200 each increase as the thickness of the separator 200 (first member 210) decreases.

[0065] Here, it is preferable that the load acting on the first member 210 (the elastic force of the first member 210) is greater than the load acting on the second member 220 (the elastic force of the second member 220) at least in a region where the thickness of the separator 200 (the first member 210) is 50% to 90% of the thickness T under no load (the region T50 to T90 in FIG. 14) (this applies to both the examples of curves 20A and 20B). It is even more preferable that the load acting on the first member 210 (the elastic force of the first member 210) is greater than the load acting on the second member 220 (the elastic force of the second member 220) at least in a region where the thickness of the separator 200 (the first member 210) is 40% to 95% of the thickness T under no load (the region T40 to T95 in FIG. 14) (this applies to both the examples of curves 20A and 20B).

[0066] In this way, the second member 220 can be provided within the practical range of the separator 200 so as not to excessively affect the deformation absorption of the first member 210.

[0067] Although the embodiments of the present technology have been described above, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present technology is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0068] 1 battery module, 1A battery pack, 10, 20A, 20B curve, 100 battery cell, 110 electrode terminal, 111 positive electrode terminal, 112 negative electrode terminal, 120 battery case, 120A case body, 120B sealing plate, 121 upper surface, 122 lower surface, 123 first side surface, 124 second side surface, 125 third side surface, 130 gas release valve, 200, 200A separator, 210, 210A first member, 211 base portion, 212 convex portion, 220, 220A second member, 221 hole portion, 300 restraining member, 400 end plate.

Claims

1. a plurality of battery cells arranged in a first direction; separators between the plurality of battery cells; a restraining member that restrains the plurality of battery cells and the separators along the first direction, The separator is a first member including a base portion and a plurality of protrusions protruding from the base portion in the first direction, the first member being made of a material having an elastic modulus of 1 MPa or more and 10 MPa or less; a second member located between the plurality of protrusions, the second member having a relatively high thermal insulation property compared to the first member and a relatively low modulus of elasticity compared to the first member; When the separator is removed from the battery pack, the protruding height of the plurality of protrusions is greater than the thickness of the second member, The battery pack, wherein the load acting on the first member is greater than the load acting on the second member at least in a region where the thickness of the separator is 50% to 90% of the thickness under no load.

2. A plurality of battery cells arranged in a first direction; separators between the plurality of battery cells; a restraining member that restrains the plurality of battery cells and the separators along the first direction, The separator is a first member including a base portion and a plurality of protrusions protruding from the base portion in the first direction; a second member located between the plurality of protrusions, having relatively high thermal insulation properties compared to the first member, and being relatively more deformable compared to the first member; The first member and the second member have substantially the same outer dimensions.

3. The battery pack according to claim 2 , wherein a protruding height of the plurality of protrusions is greater than a thickness of the second member when the separator is removed from the battery pack.

4. The battery pack according to claim 1 , wherein the base portion of the first member and the plurality of protrusions are integrally formed.

5. The battery pack according to claim 1 , wherein the second member is made of a foamed resin.

6. Providing a plurality of battery cells and separators; arranging the plurality of battery cells and the separators alternately in a first direction; and constraining the plurality of battery cells and the separators along the first direction, The step of preparing the separator includes: preparing a first member including a base portion and a plurality of protrusions protruding from the base portion in the first direction, the first member being made of a material having an elastic modulus of 1 MPa or more and 10 MPa or less; providing a second member between the plurality of protrusions, the second member having a relatively high thermal insulation property compared to the first member and a relatively low elastic modulus compared to the first member; preparing the first member includes making a protruding height of the plurality of protrusions greater than a thickness of the second member; a load acting on the first member being greater than a load acting on the second member at least in a region where the thickness of the separator is 50% to 90% of the thickness when no load is applied.

7. 7. The method for manufacturing a battery pack according to claim 6, wherein the step of preparing the separator includes foaming a resin within a recess surrounded by the continuous protrusions of the first member, thereby disposing the second member made of a foamed resin between the plurality of protrusions of the first member.

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