Battery Module

Abstract

To provide a battery module capable of achieving both suppression of increase in battery resistance and suppression of precipitation of metal.SOLUTION: A battery module includes a plurality of battery cells arranged in a first direction and a separator member provided between the plurality of battery cells. Each battery cell includes an electrode body, a housing storing the electrode body, and two electrode terminals provided on the housing to be arranged in a second direction orthogonal to the first direction. The separator member includes a body and a projection projecting from the body along the first direction. The projection height of the projection from the body is 0.05 mm or more and 0.10 mm or less. In a third direction orthogonal to the first and second directions, the size of the tip of the projection is 7.7% or more and 30.8% or less of the size of the housing.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Japanese Patent Application Publication No. 2018-060755 (Patent Document 1) discloses that when a battery cell is arranged with its electrode terminals facing upward, an increase in battery resistance is suppressed by adjusting the height of a through portion provided in a spacer (separator) so that the surface pressure applied to the lower region of the battery side wall is smaller than the surface pressure applied to the upper region.

[0003] Japanese Patent Application Laid-Open No. 2017-098107 (Patent Document 2) discloses that metal deposition in the electrode winding is suppressed by setting a low spring constant for the separator ribs (convex portions) that press against both the upper and lower ends of the electrode winding and a high spring constant for the ribs (convex portions) that press against the center of the electrode winding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-060755 A [Patent Document 2] JP 2017-098107 A Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Documents 1 and 2 disclose adjustments to the shape of the protrusions or the spring constant to individually solve the separate problems of suppressing an increase in battery resistance and suppressing metal deposition, but simply combining these technologies does not solve the two problems simultaneously.

[0006] An object of the present technology is to provide a battery module that can achieve both improved performance in terms of battery capacity or resistance and suppression of metal precipitation. [Means for solving the problem]

[0007] The present technology provides the following battery module.

[0008] [1] A battery module comprising: a plurality of battery cells arranged to be side by side in a first direction; and a separator member provided between the plurality of battery cells, wherein the battery cells include an electrode body, a housing for housing the electrode body, and two electrode terminals provided on the housing to be side by side in a second direction perpendicular to the first direction; the separator member includes a main body and a convex portion protruding from the main body along the first direction, wherein the protrusion has a protruding height from the main body of between 0.05 mm and 0.10 mm, and wherein in a third direction perpendicular to the first and second directions, the dimension of the tip of the convex portion is between 7.7 percent and 30.8 percent of the dimension of the housing.

[0009] [2] The battery module according to [1], wherein in the third direction, the dimension of the tip of the convex portion is 7.7 percent or more and 15.4 percent or less of the dimension of the housing.

[0010] [3] The battery module according to [1] or [2], wherein the protrusion is formed in an area including the center of the housing in the third direction.

[0011] [4] The battery module according to any one of [1] to [3], wherein the protrusion is formed in a strip shape extending in the second direction.

[0012] [5] A battery module described in any one of [1] to [4], wherein the electrode body has a flat portion having a flat outer surface when viewed from both the second direction and the third direction, and the convex portion is provided at a position that overlaps at least the flat portion when viewed from the first direction.

[0013] [6] The battery module according to [5], wherein the convex portion is formed over at least the entire flat portion in the second direction.

[0014] [7] The battery module according to any one of [1] to [6], wherein the protrusion has a shape in which the dimension in the third direction tapers off from the main body side toward the tip.

[0015] [8] The battery module described in any one of [1] to [7], wherein the thickness dimension of the main body in the first direction is greater than the protruding height of the convex portion.

[0016] [9] The battery module according to [8], wherein the thickness dimension is 0.25 mm or more and 0.3 mm or less. Effect of the Invention

[0017] According to the present technology, by setting the protruding height and tip dimension (width) of the protruding portion protruding from the separator body within a predetermined range, it is possible to retain the electrolyte in a balanced manner in the electrode body and effectively suppress metal deposition. As a result, a battery module is provided that can achieve both improved performance in terms of battery capacity and resistance and suppression of metal deposition. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing a basic configuration of a battery module. [Diagram 2] FIG. 2 is a perspective view showing a battery cell. [Diagram 3] FIG. 4 is a diagram showing the battery cell and the separator as viewed from the Y-axis direction. [Figure 4] FIG. 2 is a diagram showing the battery cell and separator as viewed from the X-axis direction. [Diagram 5] FIG. 13 is a diagram showing a state of a restraint experiment using a separator according to the present embodiment, as viewed from the X-axis direction. [Figure 6] FIG. 13 is a diagram showing a state of a restraint experiment using a separator according to a comparative example, as viewed from the X-axis direction. [Figure 7] 13 is a graph for explaining calculation of a restraining dimension by a restraining member. [Figure 8]FIG. 2 is a cross-sectional view showing an electrode body. [Figure 9] FIG. [Figure 10] 1 is a chart showing high-rate cycle conditions for performance evaluation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 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 will not be repeated.

[0020] In the embodiments described below, when referring to the number, amount, etc., the scope of the present technology is not necessarily limited to the number, amount, etc., unless otherwise specified. In addition, in the following embodiments, each component is not necessarily essential to the present technology, unless otherwise specified. In addition, the present technology is not necessarily limited to those that achieve all of the effects and advantages mentioned in the present embodiment.

[0021] In this specification, the words "comprise", "include" and "have" are open-ended, i.e., when a certain configuration is included, other configurations may or may not be included.

[0022] Furthermore, when geometric terms and terms expressing positional and directional relationships, such as "parallel," "orthogonal," "45° diagonal," "coaxial," and "along" are used in this specification, 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 one state, and the relative positional relationships can be inverted or rotated to any angle depending on the installation direction of each mechanism (for example, by turning the entire mechanism upside down).

[0023] In this specification, a "battery" is typically a lithium ion battery, but the concept of the present technology may also be applied to other batteries such as nickel-metal hydride batteries and sodium ion batteries. In this specification, an "electrode" may collectively refer to a positive electrode and a negative electrode. Also, an "electrode plate" may collectively refer to a positive electrode plate and a negative electrode plate.

[0024] In this specification, a "battery cell" can be mounted in a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), an electric vehicle (BEV), etc. However, the use of the "battery cell" is not limited to being mounted in a vehicle.

[0025] 1 is a diagram showing the basic configuration of a battery module 1. As shown in FIG. 1, the battery module 1 includes a battery cell 100, an end plate 200, and a restraining member 300.

[0026] The multiple battery cells 100 are arranged so as to be aligned in the Y-axis direction (first direction). This forms a stack of the battery cells 100. The battery cells 100 include electrode terminals 110. Separators (not shown) are interposed between the multiple battery cells 100. The multiple battery cells 100 sandwiched between the two end plates 200 are pressed by the end plates 200 and are restrained between the two end plates 200.

[0027] The end plates 200 are disposed on both ends of the battery module 1 in the Y-axis direction. The end plates 200 are fixed to a base such as a case that houses the battery module 1. The restraining members 300 connect the two end plates 200 to each other.

[0028] By fixing the restraining member 300 to the end plate 200 while a compressive force in the Y-axis direction is applied to the stack of multiple battery cells 100 and end plates 200, and then releasing the compressive force, a tensile force acts on the restraining member 300 connecting the two end plates 200. In reaction to this, the restraining member 300 presses the two end plates 200 in a direction that brings them closer to each other.

[0029] Fig. 2 is a perspective view showing 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 and a housing 120 (external can). In other words, the battery cell 100 is a rectangular secondary battery cell.

[0030] The electrode terminal 110 is formed on the housing 120. The electrode terminal 110 has a positive electrode terminal 111 and a negative electrode terminal 112 aligned along an X-axis direction (second direction) perpendicular to a Y-axis direction (first direction). The positive electrode terminal 111 and the negative electrode terminal 112 are provided apart from each other in the X-axis direction.

[0031] The housing 120 has a rectangular parallelepiped shape and forms the external appearance of the battery cell 100. The housing 120 includes a case body 120A that contains an electrode body and an electrolyte (not shown), and a sealing plate 120B that seals an opening of the case body 120A. The sealing plate 120B is joined to the case body 120A by welding.

[0032] The housing 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. The housing 120 is provided with a gas exhaust valve 126.

[0033] The upper surface 121 is a plane perpendicular to the Z-axis direction (third direction) 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.

[0034] Each of the first side surface 123 and the second side surface 124 is formed of 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 housing 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 with the X-axis direction being the long side direction and the Z-axis direction being the short side direction when viewed in the Y-axis direction.

[0035] 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.

[0036] Gas exhaust valve 126 is provided on top surface 121. When the temperature of battery cell 100 rises (thermal runaway) and the internal pressure of housing 120 exceeds a predetermined value due to gas generated inside housing 120, gas exhaust valve 126 exhausts the gas to the outside of housing 120.

[0037] 3 and 4 are diagrams showing the battery cell 100 and the separator 400 (separator member) as viewed from the Y-axis direction and the X-axis direction, respectively.

[0038] As shown in FIGS. 3 and 4, separator 400 includes a main body 410 and a protruding portion 420 that protrudes from the main body along the Y-axis direction.

[0039] The protruding height (T) of protrusion 420 from the main body is about 0.05 mm or more and 0.10 mm or less. The width (W) of the tip of protrusion 420 is about 7.7 percent or more and 30.8 percent or less (more preferably, about 7.7 percent or more and 15.4 percent or less) of the height (H) of case main body 120A.

[0040] In the example of FIGS. 3 and 4, convex portion 420 is formed near the center of case main body 120A in the Z-axis direction, but the installation height of convex portion 420 is not limited to the position shown in FIGS.

[0041] In the example of FIGS. 3 and 4, the convex portion 420 is formed in a strip shape extending in the X-axis direction, but the shape of the convex portion is not limited to the position shown in FIGS.

[0042] The length (L) of the band-shaped protrusion 420 in the X-axis direction can be changed as appropriate. In the example of Fig. 3 and Fig. 4, the protrusion 420 is provided at a position overlapping with a flat portion 130A of the electrode body 130 described below when viewed from the Y-axis direction. Moreover, the protrusion 420 is preferably formed over substantially the entire flat portion 130A in the X-axis direction.

[0043] It is possible to appropriately change the cross-sectional shape of the convex portion 420. In the example of Fig. 3 and Fig. 4, the width (W) of the convex portion 420 is constant from the base (main body 410 side) of the convex portion 420 toward the tip, but for example, the width (W) of the convex portion 420 may be tapered from the main body 410 side toward the tip.

[0044] Convex portion 420 may be formed integrally with main body 410, or may be formed by a separate member. For example, convex portion 420 may be formed by attaching a resin tape to main body 410 made of a resin plate. In this case, the thickness of the resin plate constituting main body 410 may be greater than, less than, or approximately the same as the protruding height of convex portion 420. In a typical example, the thickness of main body 410 is greater than the protruding height (T) of convex portion 420.

[0045] 5 and 6 are diagrams showing the state of a restraint experiment using separator 400 and separator 400A according to the present embodiment, as viewed from the X-axis direction, respectively.

[0046] In the example of FIG. 5, separators 400 each including a main body 410 and a protruding portion 420 are placed on a pair of restraining plates 500, and the protruding portion 420 is brought into contact with the case main body 120A of the battery cell 100 to press the case main body 120A.

[0047] For example, a resin plate having a thickness of about 0.25 mm or more and 0.3 mm or less can be used as main body 410. For example, double-sided tape including a PP base material can be used as protruding portion 420.

[0048] In the example of FIG. 6, separators 400A without protrusions are placed on each of a pair of restraint plates 500, and the case body 120A of the battery cell 100 is pressed against them via adhesive layers 400B.

[0049] Fig. 7 is a graph for explaining calculation of the constraint dimension of the battery cell 100. By the constraint experiment according to Fig. 5 and Fig. 6, the reaction force when the battery cell is constrained with a plurality of different constraint dimensions is measured ("Actual value" in Fig. 7), and a target constraint dimension D1 that results in a predetermined reaction force F1 (for example, 300 N) is calculated based on an approximation line. A high-rate cycle test and a lithium precipitation evaluation test, which will be described later, are performed based on this target constraint dimension D1.

[0050] FIG. 8 is a cross-sectional view showing the electrode body 130. As shown in FIG. 8, the electrode body 130 is formed by winding a stack of a positive electrode plate 131A, a negative electrode plate 131B, and a separator 133 (133A, 1333B) around the X-axis. An electrolyte solution permeates the inside of the electrode body 130. The electrode body 130 has a flat portion 130A having a flat outer surface when viewed from the X-axis direction, and a curved portion 130B having an R-shaped outer surface. The flat portion 130A is located in the center in the Z-axis direction, and the curved portions 130B are located at both ends in the Z-axis direction.

[0051] Fig. 9 is an exploded perspective view of the battery cell 100. As shown in Fig. 9, the housing 120 of the battery cell 100 has a rectangular case main body 120A and a sealing plate 120B.

[0052] The inside of the case body 120A contains an electrolyte (not shown) together with the electrode body 130. The electrode body 130 has a positive electrode 131 and a negative electrode 132 aligned in the X-axis direction. The positive electrode 131 and the negative electrode 132 located at both ends of the electrode body 130 in the X-axis direction are foil-collected so that the electrode plates are centered in the Y-axis direction. The flat portion 130A located between the positive electrode 131 and the negative electrode 132 has a flat outer surface even when viewed from the Z-axis direction.

[0053] The sealing plate 120B seals the opening of the case body 120A. Electrode terminals 110 (positive electrode terminal 111 and negative electrode terminal 112) are provided on the upper surface of the sealing plate 120B with a gap in the X-axis direction. A current collector 140 is provided on the lower surface of the sealing plate 120B. The current collector 140 includes a positive electrode side current collector 141 and a negative electrode side current collector 142. The positive electrode side current collector 141 is electrically connected to the positive electrode terminal 111. The negative electrode side current collector 142 is electrically connected to the negative electrode terminal 112.

[0054] Furthermore, the positive electrode side current collector 141 is connected to the positive electrode 131 of the electrode body 130, and the negative electrode side current collector 142 is connected to the negative electrode 132 of the electrode body 130. This electrically connects the positive electrode 131 and the negative electrode 132 of the electrode body 130 to the positive electrode terminal 111 and the negative electrode terminal 112.

[0055] Figure 10 is a chart showing the high-rate cycle for performance evaluation. The conditions of this high-rate cycle are shown in Table 1.

[0056] [Table 1]

[0057] The high-rate cycle shown in Fig. 10 was carried out under the conditions shown in Table 1, and the capacity retention rate and resistance increase rate of the battery cell 100 were measured. For the high-rate cycle test, the dimensions of the protrusions were changed and tests were carried out twice for each dimension. The capacity and resistance of the battery cell 100 were obtained under the following conditions.

[0058] [Capacity (CCCV discharge capacity charge / discharge conditions) Measured in a 25℃ thermostatic chamber (battery case bottom temperature is within 25±2℃) (1)CC-CV charging (4A / 4.1V)×2h (2) Break x 30 min (3)CC-CV discharge (2A / 3V)×3h

[0059] [Output resistance] Measured in a 25℃ thermostatic chamber (battery case bottom temperature is within 25±2℃) After adjusting to 3.706V, calculate the resistance when discharging at 130A for 10 seconds.

[0060] [Timing of acquisition] (1) Early period (2) Immediately after 9,000 cycles (3) After 5 days of cycling

[0061] As for the lithium deposition evaluation test, the dimensions of the protrusions were changed in the same manner as in the high-rate cycle test, and a test was carried out for each dimension (n=1).

[0062] The performance evaluation results obtained by the above-mentioned high-rate cycle test and lithium precipitation evaluation test are shown in Table 2. Here, the height (H) of the case body 120A of the battery cell 100 is 65.0 mm. Therefore, when W = 5 mm, W / H is approximately 0.077, when W = 10 mm, W / H is approximately 0.154, and when W = 20 mm, W / H is approximately 0.307.

[0063] [Table 2]

[0064] According to the results shown in Table 2, in Examples 1 to 3, a high capacity retention rate or a low resistance increase rate was achieved while maintaining the precipitation limit current.

[0065] In particular, in Example 2 (W=5 mm, T=0.10 mm), the same deposition limit current (120 A) as in Comparative Example 2 with "no protrusion" is maintained, while the highest capacity retention rate or the lowest resistance increase rate is achieved. It is understood that by providing an appropriate amount of space to retain the electrolyte within the wound electrode body 130, the electrolyte is prevented from entering or leaving the electrode body 130 during the charge / discharge cycle, the salt concentration distribution in the electrode body 130 is made uniform, and the resistance increase rate after the charge / discharge cycle is suppressed to a particularly low value.

[0066] Thus, according to the separator 400 of the present embodiment, by setting the protruding height (T) and the width (W) of the tip of the protruding portion 420 protruding from the main body 410 within a predetermined range (0.05 mm≦T≦0.10 mm, 0.077H≦W≦0.308H), it is possible to retain the electrolyte in a well-balanced manner in the electrode body 130 and effectively suppress the deposition of metals such as lithium. As a result, it is possible to provide a battery module 1 that achieves both improved high-rate performance regarding battery capacity or resistance and suppression of metal deposition.

[0067] Although the embodiment of the present technology has been described above, the embodiment disclosed herein should be considered as 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 scope and meaning equivalent to the claims. [Explanation of symbols]

[0068] 1 battery module, 100 battery cell, 110 electrode terminal, 111 positive electrode terminal, 112 negative electrode terminal, 120 housing, 120A case body, 120B sealing plate, 121 upper surface, 122 lower surface, 123 first side, 124 second side, 125 third side, 126 gas exhaust valve, 130 electrode body, 130A flat portion, 130B curved portion, 131 positive electrode, 131A positive electrode plate, 132 negative electrode, 132A negative electrode plate, 133, 133A, 133B separator, 140, 141, 142 current collector, 200 end plate, 300 restraining member, 400, 400A separator, 400B adhesive layer, 410 body, 420 convex portion, 500 restraining plate.

Claims

1. A plurality of battery cells arranged side by side in a first direction; a separator member provided between the plurality of battery cells; The battery cell includes an electrode body, a housing that houses the electrode body, and two electrode terminals provided on the housing so as to be aligned in a second direction perpendicular to the first direction, the separator member includes a main body and a protrusion protruding from the main body along the first direction, The protruding height of the protrusion from the main body is 0.05 mm or more and 0.10 mm or less, a dimension of a tip of the protrusion is equal to or greater than 7.7 percent and equal to or less than 15.4 percent of a dimension of the housing in a third direction perpendicular to the first direction and the second direction; The battery module, wherein the protrusion is formed near a center of the housing in the third direction.

2. The battery module according to claim 1 , wherein the protrusion is formed in a region including a center of the housing in the third direction.

3. The battery module according to claim 1 , wherein the protrusion is formed in a strip shape so as to extend in the second direction.

4. the electrode body has a flat portion having a flat outer surface when viewed from both the second direction and the third direction, The battery module according to claim 1 , wherein the protruding portion is provided at a position overlapping at least the flat portion when viewed from the first direction.

5. The battery module according to claim 4 , wherein the convex portion is formed over at least the entire flat portion in the second direction.

6. 3 . The battery module according to claim 1 , wherein the protrusion has a shape such that a dimension in the third direction decreases in a tapered manner from the main body side toward a tip end.

7. The battery module according to claim 1 or 2, wherein a thickness dimension of the main body in the first direction is greater than a protruding height of the convex portion.

8. The battery module according to claim 7 , wherein the thickness dimension is 0.25 mm or more and 0.3 mm or less.

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