Battery Module

Abstract

To provide a battery module capable of suppressing a heat propagation to an adjacent battery cell, and preventing or delaying a secure when each battery cell in the battery module occurs an abnormal heat generation.SOLUTION: In a battery module in which a plurality of battery cells is laminated via a separator, the separator comprises: two coolants; and an expansion suppression material arranged between the two coolants, and the two coolants are contacted to each battery cell.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] In recent years, with the demand for higher output and smaller size of batteries, battery cells are becoming higher capacity, while ensuring the safety of battery modules that combine multiple battery cells has become an important issue. In particular, when one of the battery cells in a battery module goes into thermal runaway, it must be avoided that the thermal chain reaction will spread to the surrounding battery cells, and ultimately the battery module will explode or catch fire.

[0003] Patent Document 1 discloses a battery pack in which a wick containing a refrigerant arranged between battery cells contacts the side of the battery cell, and when the temperature of the side of the battery cell exceeds the boiling point of the refrigerant, the refrigerant boils on the side to cool the battery cell. Patent Document 2 discloses an insulating sheet including a fiber material and an insulating material having higher insulating properties than the fiber material, and a separator that is a molded member having higher shape stability than the insulating sheet. Patent Document 3 discloses a separator including a first heat transfer member and a first thermal expansion material arranged between at least some of adjacent battery cells, the material being a foamable resin. Patent Document 4 discloses a flame-retardant insulating sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-161528 A [Patent Document 2] International Publication No. 2020-137062 [Patent Document 3] International Publication No. 2019-151037 [Patent Document 4] JP 2019-147357 A Summary of the Invention [Problem to be solved by the invention]

[0005] FIG. 3 is a schematic cross-sectional view illustrating the state of thermal runaway in a battery module using a conventional separator 20'. (a) is before thermal runaway, and (b) is after thermal runaway. As shown in FIG. 3(a), before thermal runaway, all sides of the battery cell 10 and the separator 20' arranged between the adjacent battery cells 10 are stacked in parallel. However, as shown in FIG. 3(b), after thermal runaway of the central battery cell 10, expansion occurs at the side 10a of the central battery cell 10, the separator 20' arranged in contact with the central battery cell 10 is crushed, and the distance between the side 10a of the central battery cell 10 and the side 10b of the adjacent battery cell 10 becomes closer, and there is a risk that the suppression of heat transfer from the thermal runaway battery cell 10 to the adjacent battery cell will not be sufficient. In addition, the insufficient suppression of heat transfer by the separator 20' may cause expansion at the side 10b of the adjacent battery cell 10, which may cause further thermal runaway. The expansion of the side surfaces 10a and 10b of the battery cell 10 due to abnormal heat generation is particularly noticeable in the center of the side surfaces.

[0006] Therefore, in consideration of the above-mentioned situation, an object of the present disclosure is to provide a battery module that can suppress heat transmission to adjacent battery cells and prevent or delay the spread of fire when a battery cell within the battery module generates abnormal heat. [Means for solving the problem]

[0007] As one means for solving the above problems, the present disclosure provides a battery module in which a plurality of battery cells are stacked with a separator interposed therebetween, the separator comprising two coolants and an expansion inhibitor disposed between the two coolants, and the two coolants are in contact with the battery cells. Effect of the Invention

[0008] According to the battery module of the present disclosure, when a battery cell in the battery module generates abnormal heat, the heat transfer to adjacent battery cells can be suppressed, thereby preventing or delaying the spread of fire. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic perspective view of a battery module 100 according to an embodiment. [Diagram 2] 2 is a schematic cross-sectional view of three adjacent battery cells taken along the II plane of the battery module 100 in Fig. 1. (a) shows the state before thermal runaway, and (b) shows the state after thermal runaway. [Diagram 3] 1A and 1B are schematic cross-sectional views illustrating the state of thermal runaway in a battery module using a conventional separator, (a) showing the state before thermal runaway and (b) showing the state after thermal runaway. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the embodiment described below is merely an example for embodying the technical concept of the present invention, and the present invention is not limited to the embodiment described below.

[0011] [Battery module] A battery module uses multiple battery cells, connects them in series or parallel, and adjusts the capacity and voltage. Fig. 1 is a schematic perspective view of a battery module 100 according to one embodiment. As shown in Fig. 1, the battery module 100 includes multiple stacked battery cells 10, separators 20 interposed between adjacent battery cells, and end plates 40 disposed at both ends of the multiple stacked battery cells 10. Hereinafter, the direction in which the battery cells 10 are stacked is also referred to as the thickness direction. 2 is a schematic cross-sectional view of three adjacent battery cells when the battery module 100 in FIG. 1 is cut along plane II. (a) is before thermal runaway, and (b) is after thermal runaway. As shown in FIG. 2(a) and FIG. 2(b), a separator 20 interposed between adjacent battery cells is formed of two coolants 21 and an expansion suppression material 22 disposed between the two coolants 21. The battery module 100 may be housed in a battery case, or the battery module 100 may be provided in an internal space sealed by an outer wall of the battery case.

[0012] <Battery cell> FIG. 1 shows five rectangular battery cells 10 arranged in parallel such that the sides of adjacent battery cells perpendicular to the thickness direction are all parallel. The battery cells 10 may be known secondary battery cells each having a pair of electrode terminals consisting of a positive terminal 11 and a negative terminal 12 and a secondary battery body 13, and examples of such secondary battery cells include lithium ion secondary batteries, nickel hydride secondary batteries, and nickel cadmium secondary batteries. The shape of the battery cells 10 may be any shape that allows multiple battery cells 10 to be stacked, and examples of such shapes include cylindrical, rectangular, and laminated types. For example, when the battery cells 10 are rectangular batteries, a bus bar is used, and when the battery cells 10 are laminated batteries, the tab leads themselves are ultrasonically welded to form the battery module 100. The battery module 100 may have more than one battery cell 10, with no limit on the number. The battery cell arrangement may be such that a separator 20 formed of two coolants 21 and an expansion inhibitor 22 disposed between the two coolants 21 is disposed between adjacent battery cells, with no limit on the connection state, and the battery cells may be connected in series, in parallel, or a mixture of both.

[0013] <separator> The separators 20 are disposed between each of the stacked battery cells 10, and are components that insulate adjacent battery cells from each other. Note that the function of insulating adjacent battery cells from each other may be achieved by covering the surfaces of the battery cells 10 with an insulating material. As shown in Fig. 2, the separator 20 is formed from two coolants 21 and an expansion-suppressing material 22 disposed between the two coolants 21.

[0014] <Coolant> The coolant 21 is a member that cools battery cells 10 that have generated abnormal heat, and is in the form of a plate or film. The two coolants 21 have two side surfaces that are perpendicular to the thickness direction. One side of the coolant 21 is arranged so as to contact the opposing surfaces of adjacent battery cells 10, and the other side of the coolant 21 is arranged so as to contact an expansion-suppressing material 22, which will be described later. In other words, the two coolants 21 are arranged so as to sandwich the expansion-suppressing material 22 and to be interposed as a separator 20 between the opposing surfaces of adjacent battery cells 10. The side surfaces of the battery cells 10 and the side surfaces of the coolant 21 are all arranged so as to be parallel to each other in a plane perpendicular to the thickness direction.

[0015] The coolant 21 is a member that suppresses heat generation from the battery cells 10, and may be made of any material that is flame-retardant and has a cooling effect, such as a metal plate made of aluminum, iron, copper, stainless steel, or the like with an insulating film. An example of the insulating film is polytetrafluoroethylene (PTFE), which coats the metal plate with a fluororesin coating or the like. Note that the coolant 21 does not need to have an insulating function as long as the surface of the battery cells 10 is covered with an insulating material.

[0016] Furthermore, because heat is generated in the entire battery cell 10, it is preferable that the coolant 21 cools the entire battery cell 10. In other words, it is sufficient for the coolant 21 to be able to cool the entire battery cell 10, and although the side shape of the coolant 21 may be different from the side shape of the battery cell 10, it is preferable that the side shape of the coolant 21 is approximately the same as the side shape of the battery cell 10. Depending on the material and thickness of the coolant 21, for example, if the coolant is an aluminum plate with a thickness of 1 mm, the side area of ​​the coolant 21 may be approximately 70% to 100% of the side area of ​​the battery cell 10.

[0017] The thickness of the coolant 21 is preferably 0.5 mm or more from the viewpoint of ensuring cooling performance, and is preferably 2 mm or less from the viewpoint of miniaturization for mounting on a vehicle.

[0018] <Expansion suppression material> The expansion-suppressing material 22 is plate-like or film-like, and has two side surfaces perpendicular to the thickness direction. Both side surfaces of the expansion-suppressing material 22 are arranged so as to be sandwiched between two coolants 21 that are arranged so as to be in contact with the opposing surfaces of adjacent battery cells 10. The expansion-suppressing material 22 is preferably arranged in the center of the side surface of the battery cell 10 where the expansion of the battery cell 10 becomes noticeable due to abnormal heat generation.

[0019] The expansion-suppressing material 22 is a member that suppresses expansion due to heat generation from the battery cells 10, and may be made of any flame-retardant material, such as phenolic resin, glass wool, rock wool, gypsum, diatomaceous earth, or flame-retardant fiber.

[0020] By providing a wide non-contact area between the two pieces of coolant 21 that sandwich both sides of the expansion-inhibiting material 22, the air layer in the non-contact area enhances the insulating effect, so it is preferable to reduce the side area of ​​the expansion-inhibiting material 22. In addition, it is preferable that the expansion-inhibiting material 22 has a strength that can suppress expansion of the center portion due to abnormal heat generation of the adjacent battery cells 10 to a certain amount. The side area of ​​the expansion-inhibiting material 22 may be approximately 20% to 50% of the side area, depending on the strength of the coolant 21.

[0021] The thickness of the expansion suppressing material 22 is preferably 0.5 mm or more from the viewpoint of ensuring expansion suppression, and is preferably 2 mm or less from the viewpoint of miniaturization for mounting on a vehicle. Expansion of the battery cell may occur not only in the battery cell that has undergone thermal runaway, but also in adjacent battery cells due to heat received from the battery cell that has undergone thermal runaway. In particular, when the battery cell generates abnormal heat, the expansion of the center of the side of the battery cell is remarkable. Therefore, by sandwiching the expansion suppressing material 22 in the center of the side between the two coolants 21, the expansion of the battery cell 10 can be suppressed to a certain amount. Furthermore, by suppressing the expansion of the battery cell 10 to a certain amount, the two coolants 21 arranged on both sides of the expansion suppressing material 22 can be prevented from contacting each other. This ensures an air layer between the two coolants 21, and suppresses heat transmission from the battery cell that has generated abnormal heat to the adjacent battery cell.

[0022] The expansion suppressor 22 may be sandwiched between the two coolants 21 at the center of the side surface, and the shape of the side surface is not particularly limited, and may be, for example, a square, a rectangle, a polygon, a circle, an ellipse, etc., but a circle is preferable. If it is a circle, pressure is less likely to be applied to the edge of the side surface. The expansion-suppressing material 22 can be arranged in the center of the side surface between the two coolants 21, for example, by adhering with tape. The stacked battery cells 10 and separators 20 are restrained by end plates (described below) and a certain amount of pressure is applied between the battery cells 10. If thermal expansion occurs, the restraining pressure will increase, so the material may be fixed to the extent that positioning is possible.

[0023] <End plate> The multiple battery cells 10 and multiple separators 20, which are alternately stacked with their side faces facing each other, are restrained by a pair of end plates 40 and fasteners (not shown). The end plates 40 can be any known end plates without any restrictions, and examples of such end plates include metal plates made of aluminum, iron, copper, etc., and are insulated from the battery cells 10 by being adjacent to the battery cells 10 via the separators 20. Note that the surface of the end plates 40 may be coated with an insulating material to be adjacent to the battery cells 10. The stacked battery cells 10 and separators 20 are held together by the end plates 40 using known fasteners. EXAMPLES

[0024] [Battery module for evaluation] An evaluation battery module consisting of five electronic cells as shown in FIG. 1 was produced. In Examples 1 to 6 and Comparative Example 1, the same battery cells were used, and the side size of the battery cells was 148 mm×90 mm. In Examples 1 to 6, a coolant 21 and an expansion suppressing material 22 were arranged between the battery cells as separators between the battery cells. In Comparative Example 1, the coolant 21 and the expansion suppressing material 22 were not used, and a 3 mm thick polypropylene (PP) resin whose side size is the same as the side size of the battery cells in both length and width was used as a separator between the battery cells. In Examples 1 to 6, the coolant was a stainless steel (SUS) plate whose side size is the same as the side size of the battery cells in both length and width, and the expansion suppressing material was a phenolic resin whose side size is 2 cm×2 cm. The expansion suppressing material was arranged in the center of the side of the coolant, and the thicknesses of the coolant 21 and the expansion suppressing material 22 in Examples 1 to 6 are as shown in Table 1. Table 1 shows the thickness of each component of the battery cell separator in Examples 1 to 6 and Comparative Example 1, and the results of the nail penetration thermal chain test described below.

[0025] [Table 1]

[0026] [Nail penetration thermal chain test] One type of safety test is a nail penetration test, which is a simulation test of an internal short circuit, in which a nail is penetrated into a battery to simulate an internal short circuit and to confirm that the battery does not catch fire or explode. For the evaluation battery modules of Examples 1 to 6 and Comparative Example 1, a thermal chain test was carried out using the nail penetration of the center battery cell as a trigger.

[0027] The conditions for the nail penetration thermal chain test are as follows: <Condition> ·Nail: Φ6mm, tip angle 60° ·Nail speed: 2mm / sec ·Starting SOC (State of Charge): 100%

[0028] [result] Table 1 shows the ratio of the time from nail penetration to chain smoking of the central battery cells in Examples 1 to 6, when the time from nail penetration to chain smoking of the central battery cell in Comparative Example 1 is taken as 1. As shown in Table 1, in Examples 1 to 5, the time from nail penetration to chain smoking of the central battery cell is 1.9 to 5.7 times that of Comparative Example 1, and heat transfer to adjacent battery cells is suppressed and chain smoking (spread of fire) is delayed. Furthermore, in Example 6, chain smoking due to thermal chain is prevented. In other words, according to the battery module of the present disclosure, when a battery cell in the battery module generates abnormal heat, heat transfer to adjacent battery cells can be suppressed and spreading of fire can be prevented or delayed. [Industrial Applicability]

[0029] The battery module of the present disclosure can be widely used as a power source for a wide range of applications, from large power sources for vehicle installation to small power sources for mobile terminals. [Explanation of symbols]

[0030] 10 Battery Cells 10a, 10b side 11 Positive terminal 12 Negative terminal 13 Secondary battery body 20, 20´ separator 21 Coolant 22 Expansion inhibitor 40 End Plate 100 Battery Module

Claims

[Claim 1] A battery module in which a plurality of battery cells are stacked with separators interposed therebetween, the separator includes two coolants and an expansion suppressor disposed between the two coolants at the center of a side surface of the battery cell, the two coolants being in contact with the battery cell; the cooling material is a plate-like or film-like member having two side surfaces perpendicular to a thickness direction, one of the side surfaces being in contact with the battery cell, and the thickness of the cooling material is 1 mm or more; Battery module.

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