Battery Module

Abstract

To provide a battery module capable of increasing energy density and maintaining surface stress relatively constant even when a solid battery cell is charged.SOLUTION: A battery module 10 includes a battery cell stack 11 in which a plurality of battery cells 11a is stacked, a pair of end plates 12 provided at both ends of the battery cell stack 11 in the stacking direction, and a cushioning material 14 sandwiched between the plurality of battery cells 11a and / or between the battery cell 11a and the end plate 12. The cushioning material 14 includes a viscoelastic material. The battery module 10 further includes a displacement allowing unit 15 that allows the cushioning material 14 to be displaced to the outside of the battery cell stack 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In light of climate-related disasters, there is growing interest in electric vehicles in order to reduce CO2 emissions, and the installation of battery modules having battery cell stacks in which multiple battery cells are stacked on top of each other in electric vehicles is being considered.

[0003] Since battery cells expand and contract as they are charged and discharged, the battery module is equipped with a pair of end plates provided at both ends of the battery cell stack in the stacking direction, and a bind bar that restrains the battery cell stack between the pair of end plates (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-051876 Summary of the Invention [Problem to be solved by the invention]

[0005] However, solid-state battery cells (especially lithium metal solid-state battery cells) undergo large volume changes during charging and discharging, which causes changes in the dimensions of the battery module, making it difficult to mount them on a vehicle.

[0006] Therefore, in order to deform in accordance with the volume change of the solid-state battery cells, it is conceivable to place cushioning material between the solid-state battery cells and / or between the solid-state battery cells and the end plates, but this would result in a lower energy density.

[0007] On the other hand, it is desirable that the surface stress remains relatively constant even when the solid-state battery cell is charged and expands, i.e., that there exists a plateau region of the surface stress.

[0008] An object of the present invention is to provide a battery module that can increase energy density and maintain a relatively constant surface stress even when the solid-state battery cells are charged. [Means for solving the problem]

[0009] One aspect of the present invention is a battery module comprising: a battery cell stack in which a plurality of battery cells are stacked; a pair of plate-shaped members provided at both ends of the battery cell stack in the stacking direction; and a cushioning material sandwiched between the plurality of battery cells and / or between the battery cells and the plate-shaped members, wherein the cushioning material includes a viscoelastic material and further comprises a displacement-allowing portion that allows displacement of the cushioning material outside the battery cell stack.

[0010] The viscoelastic material may be a polyurethane-based thermoplastic elastomer.

[0011] The cushioning material may have fine particles or lubricating oil present on the surface.

[0012] The fine particles may be talc powder.

[0013] The battery module may further include a restoration promotion mechanism that promotes restoration of the cushion material that has been displaced to the outside of the battery cell stack. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a battery module that can increase energy density and maintain a relatively constant surface stress even when the solid-state battery cells are charged. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view showing an example of a battery module according to an embodiment of the present invention. [Figure 2] FIG. 2 is a partially enlarged view of the battery module of FIG. [Figure 3] FIG. 10 is a partially enlarged view of a battery module that does not have a displacement allowance portion. [Figure 4] 1. FIG. 4 is a cross-sectional view showing a modified example of the battery module of FIG. [Figure 5] FIG. 1 is a cross-sectional view showing a test piece of Example 1. [Figure 6] FIG. 2 is a cross-sectional view showing a test piece of Comparative Example 1. [Figure 7] 1 is a graph showing the relationship between the surface stress and the compressive displacement of the cushioning materials of Examples 1 and 2 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] FIG. 1 shows an example of a battery module according to this embodiment.

[0018] The battery module 10 includes a battery cell stack 11 in which a plurality of battery cells 11a are stacked, end plates 12 as a pair of plate-like members provided at both ends of the battery cell stack 11 in the stacking direction, and bind bars 13 as restraining members that restrain the battery cell stack 11 between the pair of end plates 12. Here, the bind bars 13 are installed in two places, at the top and bottom in the drawing.

[0019] In the battery module 10, cushioning materials 14 are sandwiched between the plurality of battery cells 11a and between the battery cells 11a and the end plates 12, and the cushioning materials 14 include a viscoelastic material. Here, even if the viscoelastic material is thin, it can absorb the surface stress generated by the expansion and contraction of the battery cells 11a relatively consistently, thereby increasing the energy density of the battery module 10.

[0020] The cushion material 14 may be sandwiched between the plurality of battery cells 11a or between the battery cell 11a and the end plate 12.

[0021] The viscoelastic material is not particularly limited, but examples thereof include rubbers such as silicone rubber, ethylene propylene diene rubber (EPDM), styrene butadiene rubber (SBR), and nitrile rubber (NBR), and elastomers such as polyurethane thermoplastic elastomer (TPU), polyamide thermoplastic elastomer (TPA), polyester thermoplastic elastomer (TPC), olefin thermoplastic elastomer (TPO), styrene thermoplastic elastomer (TPS), and dynamically crosslinked thermoplastic elastomer (TPV). Among these, polyurethane thermoplastic elastomers are preferred because of their large deformation capacity.

[0022] 2, the battery module 10 further includes a displacement allowance portion 15 that allows displacement of the cushion material 14 toward the outside (vertical direction in the figure) of the battery cell stack 11. Therefore, even when the battery cell 11a is charged and expands, the cushion material 14 is displaced toward the displacement allowance portion 15, so that the stress is dispersed and the surface stress is maintained relatively constant, that is, a plateau region of the surface stress exists.

[0023] In this specification and claims, the "outside of the battery cell stack" refers to the area that exists outside the battery cells when viewed from above in the stacking direction of the battery cells. For example, the displacement allowance portion 15 corresponding to the cushion material 14 sandwiched between the battery cells 11a is disposed between the battery cell stack 11 and the bind bar 13.

[0024] In contrast, as shown in Figure 3, if the displacement-tolerant portion 15 is not present, when the battery cell 11a is charged and expands, the stress is not dispersed, the surface stress increases quadratically, and there is no plateau region of the surface stress.

[0025] It is preferable that fine particles or lubricating oil are present on the surface of the cushioning material 14. This reduces the coefficient of friction of the cushioning material 14 and increases the plateau region of the surface stress.

[0026] The fine particles are not particularly limited as long as they can reduce the coefficient of friction of the cushioning material 14, and examples thereof include inorganic fine particles such as talc powder, silica powder, and calcium silicate, and organic fine particles such as acrylic resin, melamine resin, wheat flour, and potato starch. Among these, talc powder is preferred in terms of chemical stability and availability.

[0027] The particle size of the fine particles is not particularly limited, but is, for example, 40 μm or less.

[0028] The lubricating oil is not particularly limited as long as it can reduce the coefficient of friction of the cushion material 14. Note that grease, which is a lubricating oil to which a thickener and an additive have been added, may be present on the surface of the cushion material 14.

[0029] The battery module 10 preferably further includes a restoration promotion mechanism that promotes restoration of the cushion material 14 that has been displaced to the outside of the battery cell stack 11. This reduces hysteresis loss of the cushion material 14.

[0030] The restoration promotion mechanism is not particularly limited as long as it can promote the restoration of the cushion material 14 that has been displaced to the outside of the battery cell stack 11, and examples thereof include potting material, springs, etc. Among these, springs are preferred because of their low friction.

[0031] For example, by applying a potting process to the bind bar 13, the potting material 21 is disposed between the bind bar 13 and the cushion material 14 and the battery cell 11a (see FIG. 4(a)). At this time, a lightening portion (air) may be formed on the surface of the potting material 21 that comes into contact with the bind bar 13. The material that constitutes the potting material 21 is not particularly limited, but examples thereof include urethane resin, epoxy resin, and silicone resin.

[0032] Furthermore, a spring 23 is disposed between the bind bar 13 and the cushion material 14 and battery cell 11a via a plate-like member 22 (see FIG. 4(b)). The material constituting the plate-like member 22 is not particularly limited, but examples thereof include metal, resin, etc. The material constituting the spring 23 is not particularly limited, but examples thereof include metal, etc.

[0033] The battery cells 11a are not particularly limited, but examples thereof include non-aqueous electrolyte battery cells, solid battery cells, etc. The battery module 10 maintains a relatively constant surface stress even when the battery cells 11a are charged, and is therefore particularly effective when solid battery cells (especially lithium metal solid battery cells) that expand and contract significantly due to charging and discharging are used as the battery cells 11a.

[0034] Examples of solid-state batteries include semi-solid lithium ion batteries, all-solid lithium ion batteries, semi-solid lithium metal batteries, and all-solid lithium metal batteries.

[0035] Hereinafter, a case where the solid-state battery is an all-solid-state lithium metal battery will be described.

[0036] An all-solid-state lithium metal battery includes, for example, a positive electrode current collector, a positive electrode mixture layer, a solid electrolyte layer, a lithium metal layer, and a negative electrode current collector, which are stacked in this order.

[0037] The positive electrode current collector is not particularly limited, but may be, for example, aluminum foil.

[0038] The positive electrode mixture layer contains a positive electrode active material, and may further contain a solid electrolyte, a conductive additive, a binder, and the like.

[0039] The positive electrode active material is not particularly limited as long as it can absorb and release lithium ions. For example, LiCoO2, Li(Ni 5 / 10 Co 2 / 10 Mn 3 / 10 )O 2、 Li(Ni) 6 / 10 Co 2 / 10 Mn 2 / 10 )O 2、 Li(Ni) 8 / 10 Co 1 / 10 Mn 1 / 10 )O 2、 Li(Ni) 0.8 Co 0.15 Al 0.05 )O 2、 Li(Ni) 1 / 6 Co 4 / 6 Mn 1 / 6 )O 2、 Li(Ni) 1 / 3 Co 1 / 3 Mn 1 / 3 )O 2、 Examples include LiCoO4, LiMn2O4, LiNiO2, LiFePO4, lithium sulfide, and sulfur.

[0040] The solid electrolyte constituting the solid electrolyte layer is not particularly limited as long as it is a material capable of conducting lithium ions, and examples thereof include oxide-based electrolytes and sulfide-based electrolytes.

[0041] The negative electrode current collector is not particularly limited, but examples thereof include copper foil.

[0042] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate within the scope of the spirit of the present invention. [Example]

[0043] Examples of the present invention will be described below, but the present invention is not limited to these examples. Because it is difficult to directly evaluate the surface stress of a battery module, in these examples, a test piece simulating a battery module was used to evaluate the relationship between the surface stress and the compressive displacement of the cushioning material.

[0044] [Example 1] A polyurethane elastomer (manufactured by Exseal) with a hardness of Asker C7 was sandwiched between two jigs 41 each having a length of 52 mm and a width of 70 mm and a thickness of 5 mm to obtain a test specimen (see FIG. 5). The test specimen of Example 1 has a displacement allowance portion that allows displacement of the jig 41 outward (in the left-right direction in the figure).

[0045] [Example 2] A test piece was obtained in the same manner as in Example 1, except that a polyurethane elastomer (manufactured by Exseal) with talc powder applied to the surface was used as the cushioning material 42.

[0046] [Comparative Example 1] A test piece was obtained by sandwiching a polyurethane elastomer (manufactured by Exseal) with a hardness of Asker C7 as cushioning material 52, measuring 20 mm in length, 20 mm in width, and 5 mm in thickness, between jigs 51 measuring 52 mm in length and 70 mm in width (see FIG. 6). Here, the test piece of Comparative Example 1 does not have a displacement allowance portion that allows jig 51 to be displaced outward because the surface area of ​​cushioning material 52 is smaller than the surface area of ​​jig 51.

[0047] Comparative Example 2 A test piece was obtained in the same manner as in Comparative Example 1, except that a polyurethane elastomer (manufactured by Exseal) with talc powder applied to the surface was used as the cushioning material 52.

[0048] [Coefficient of friction of cushioning material] Using a digital force gauge ZTA-1000N (manufactured by Imada), the maximum static friction coefficients in the planar direction of the cushioning materials 42 in Examples 1 and 2 were measured and found to be 1.758 and 0.015, respectively. This shows that applying talc powder to the surface of the urethane gel reduces the friction coefficient.

[0049] [Relationship between surface stress and compressive displacement of cushioning material] Using a servopulsar (Shimadzu Corporation) and a 10 kN load cell, the relationship between the surface stress and the compressive displacement of the cushioning material was measured. Specifically, the cushioning material was compressed at a compression speed of 0.002 mm / s until the compressive displacement reached 70%.

[0050] FIG. 7 shows the relationship between the surface stress and the compressive displacement of the cushioning materials of Examples 1 and 2 and Comparative Examples 1 and 2.

[0051] 7 shows that in Examples 1 and 2, the surface stress remains relatively constant, i.e., a plateau region of the surface stress exists, even when the cushion material 42 is compressed. For this reason, it is presumed that a battery module having a structure similar to that of the test specimens in Examples 1 and 2 will maintain a relatively constant surface stress even when the solid-state battery cells are charged.

[0052] In contrast, the test pieces of Comparative Examples 1 and 2 do not have a displacement allowance portion that allows displacement of the jig 51 outward, so when the cushion material 52 is compressed, the surface stress increases quadratically, and there is no plateau region of the surface stress. In Comparative Examples 1 and 2, cuts occurred on the side edge of the cushion material 52. This is presumably because a maximum stress portion occurred in the cushion material 52, preventing the stress from being dispersed. [Explanation of symbols]

[0053] 10 Battery Module 11 Battery cell stack 11a battery cell 12 End plate 13 Binding Bar 14 Cushioning material 15 Displacement allowance section 21 Potting material 22 Plate-shaped member 23 Spring 41, 51 Jig 42, 52 Cushioning material

Claims

1. a battery cell stack in which a plurality of battery cells are stacked; a pair of plate-shaped members provided at both ends of the battery cell stack in a stacking direction; a cushioning material sandwiched between the plurality of battery cells and / or between the battery cells and the plate-shaped member, the cushioning material includes a viscoelastic material and has fine particles or a lubricating oil present on the surface thereof; The battery module further includes a displacement allowing portion that allows the cushion material to be displaced outward from the battery cell stack.

2. The battery module according to claim 1 , wherein the fine particles are talc powder.

3. a battery cell stack in which a plurality of battery cells are stacked; a pair of plate-shaped members provided at both ends of the battery cell stack in a stacking direction; a cushioning material sandwiched between the plurality of battery cells and / or between the battery cells and the plate-shaped member, the cushioning material includes a viscoelastic material; a displacement allowing portion that allows the cushion material to be displaced outward from the battery cell stack; a restoration promotion mechanism that promotes restoration of the cushion material that has been displaced to the outside of the battery cell stack.

4. The battery module according to claim 1 , wherein the viscoelastic material is a polyurethane-based thermoplastic elastomer.

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