Battery pack

Abstract

The present invention addresses the problem of providing a battery pack in which battery cells are easy to slide within a case. In order to solve the problem, a battery pack is provided with a plurality of battery cells and a case. The case accommodates a battery stack in which battery cells are stacked in a predetermined stacking direction. Each battery cell has a curved surface that connects a bottom surface and a side surface on the width direction side orthogonal to the stacking direction. The battery pack is further provided with a heat-conducting sheet on each battery cell. Each heat-conducting sheet has a heat-conducting layer and a sliding layer having a lower coefficient of friction than the heat-conducting layer. The surface on the heat-conducting layer side in each heat-conducting sheet is mounted on the battery cell so as to cover a portion including the bottom surface and the curved surface in the battery cell. The sliding layer abuts against the inner bottom face of the shell.

Description

Technical Field

[0001] The present invention relates to a battery pack containing a plurality of battery cells. Background Art

[0002] In recent years, from the viewpoints of reducing carbon dioxide emissions and reducing adverse effects on the global environment, electric vehicles such as electric vehicles (EV) and hybrid electric vehicles (HEV) have been popularized. Among the battery packs mounted on electric vehicles and the like, there are battery packs including a battery laminate and a case. The battery laminate is formed by laminating a plurality of battery cells in a specified lamination direction. The case houses the battery laminate.

[0003] [Prior Art Documents]

[0004] (Patent Documents)

[0005] Patent Document 1: International Publication No. 2021 / 070478 Summary of the Invention

[0006] [Problems to be Solved by the Invention]

[0007] In such a battery pack, there is a case where a heat conductive sheet is disposed between the bottom surface of the battery laminate and the inner bottom surface of the case. In this case, the present inventors have focused on the following problem that may occur if the heat conductive sheet is adhered to the inner bottom surface of the case.

[0008] When a battery cell is placed on the heat conductive sheet, the heat conductive sheet is elastically deformed due to the weight of the battery cell and a concave portion is formed. The bottom of the battery cell is fitted into the concave portion, and thus it is difficult for the battery cell to slide on the heat conductive sheet.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to make it easy for the battery cells to slide within the case.

[0010] [Means for Solving the Problems]

[0011] The present inventors have found that if a heat conductive sheet is provided on each battery cell, and a heat conductive layer and a sliding layer having a friction coefficient smaller than that of the heat conductive layer are provided on each heat conductive sheet, the above object can be achieved, and thus the present invention has been completed. The present invention is the following battery packs (1) to (4).

[0012] (1) A battery pack,

[0013] comprising: a plurality of battery cells; and a case housing a battery laminate in which the battery cells are laminated in a specified lamination direction;

[0014] Each of the foregoing battery cells has a curved surface that connects the side surface and the bottom surface on the width direction side orthogonal to the foregoing stacking direction; wherein,

[0015] Each of the foregoing battery cells is provided with a heat conducting sheet,

[0016] Each of the foregoing heat conducting sheets has a heat conducting layer and a sliding layer with a friction coefficient smaller than that of the foregoing heat conducting layer,

[0017] The surface on the heat conducting layer side of each of the foregoing heat conducting sheets is mounted on the battery cell in such a way as to cover a part including the foregoing bottom surface and the foregoing curved surface in the foregoing battery cell,

[0018] The foregoing sliding layer abuts against the inner bottom surface of the foregoing housing.

[0019] According to this configuration, the sliding layer with a friction coefficient smaller than that of the heat conducting layer abuts against the inner bottom surface of the housing. Moreover, the heat conducting sheet is mounted on each battery cell with respect to the bottom surface of the battery cell rather than the inner bottom surface of the housing. Therefore, it is possible to suppress the drawback that a concave portion is formed on the heat conducting sheet due to the weight of the battery cell and the bottom portion of the battery cell is embedded in the concave portion. Thus, the battery cell can slide easily in the housing.

[0020] Moreover, each heat conducting sheet is mounted on the battery cell in such a way as to cover not only the bottom surface of the battery cell but also the curved surface. Thus, the end portion of each heat conducting sheet is mounted on the curved surface or the side surface of the battery cell and is not easily rubbed against the inner bottom surface of the housing. Therefore, it is possible to suppress the drawback that the heat conducting sheet peels off from the end portion. Thus, the peeling of the heat conducting sheet can be suppressed.

[0021] (2) The battery pack according to the foregoing (1), wherein a plurality of the foregoing battery laminates are accommodated side by side in the foregoing width direction in the foregoing housing,

[0022] The state formed by the foregoing heat conducting sheet when no external force is applied to the foregoing heat conducting sheet is defined as the natural state of the sheet,

[0023] Assuming the foregoing natural state of the sheet, a plurality of the foregoing battery laminates are arranged in such a way that the foregoing heat conducting sheets adjacent to each other in the foregoing width direction overlap each other.

[0024] According to this configuration, by overlapping the heat conducting sheets, the heat conducting sheets are elastically deformed and protrude into the gaps such as below the overlapping region. Thus, it is possible to reduce the gap and improve the heat conduction performance from the battery cell to the bottom of the housing.

[0025] (3) The battery pack according to the foregoing (2), wherein the region where the foregoing heat conducting sheets arranged in the foregoing width direction overlap each other assuming the foregoing natural state of the sheet is defined as the overlapping region,

[0026] The area formed below the overlapping area, i.e., the area surrounded by the two thermally conductive sheets arranged along the width direction and the inner bottom surface, assuming that the sheet is in a natural state, is defined as a gap area.

[0027] The plurality of battery stacks are arranged such that the area of ​​the overlapping region is smaller than the area of ​​the gap region when viewed in the stacking direction.

[0028] According to this configuration, when the heat conductive sheet is elastically deformed due to overlapping, the protruding portion of the heat conductive sheet caused by the elastic deformation is accommodated in the gap area. Therefore, the disadvantage that the protruding portion of the heat conductive sheet has nowhere to go and protrudes to the bottom side of the housing is suppressed. As a result, the disadvantage of hindering the sliding of the battery cell relative to the inner bottom surface of the housing is suppressed. Therefore, the sliding property of the battery cell relative to the inner bottom surface of the housing can be ensured.

[0029] (4) The battery pack according to any one of (1) to (3), wherein the sliding layer is a polyethylene terephthalate film.

[0030] Polyethylene terephthalate film is excellent in both low friction and insulation properties. Therefore, according to this configuration, the sliding layer of the thermally conductive sheet can have both low friction and insulation properties.

[0031] [Effects of the invention]

[0032] As described above, according to the configuration of (1), the battery cell can be easily slid in the case. Furthermore, according to the configurations of (2) to (4) referring to (1), respective additional effects can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a perspective view showing a battery pack according to this embodiment.

[0034] Figure 2 It is a perspective view showing a battery stack and a thermally conductive sheet.

[0035] Figure 3 The figure shows an exploded perspective view of a battery pack.

[0036] Figure 4 A side cross-sectional view of a battery pack is shown.

[0037] Figure 5 It is an exploded front view showing a battery cell.

[0038] Figure 6 This is a front view showing the natural state of the sheets in the battery cells arranged along the X direction.

[0039] Figure 7It is a front view showing parts between battery cells arranged in the X direction. Detailed Embodiment

[0040] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments in any way and can be implemented with appropriate modifications without departing from the gist of the present invention.

[0041] [First Embodiment]

[0042] As Figure 1 shown, the battery pack 100 includes two battery laminates Bs, a plurality of bus bars 50, a housing 80, a port member 85, and a pressure plate 87.

[0043] Hereinafter, two specified directions orthogonal to each other in the horizontal plane will be referred to as the "X direction" and the "Y direction". In addition, one of the X directions will be referred to as the "X - direction", and its opposite direction will be referred to as the "X + direction". In addition, one of the Y directions will be referred to as the "Y - direction", and its opposite direction will be referred to as the "Y + direction".

[0044] As Figure 3 shown, the housing 80 has a box - shaped shape that is open upward and houses the two battery laminates Bs arranged in the X direction. The material of the housing 80 is metal or the like. A through - hole - shaped pressure window 82 is provided at the end of the housing 80 on the Y - direction side.

[0045] As Figure 2 shown, each battery laminate Bs includes a plurality of battery cells 70, a plurality of separators 79, and end plates 78. Each battery cell 70 has a rectangular outer package. Specifically, for each battery cell 70, the X direction is set as the width direction, the Y direction is set as the depth direction, and the up - and - down direction is set as the height direction. Thus, the "X direction" can also be referred to as the "width direction". In each battery laminate Bs, the battery cells 70 are stacked in the Y direction. Thus, the "Y direction" can also be referred to as the "stacking direction". The separators 79 are arranged between every two battery cells 70 arranged in the Y direction. The end plates 78 are provided closer to the Y - direction side than the lowermost battery cell 70 in the Y - direction. The materials of the separators 79 and the end plates 78 are resin or the like.

[0046] In each battery laminate Bs, the plurality of battery cells 70, the plurality of separators 79, and the end plates 78 are joined together by an adhesive (not shown) which is a frame - shaped member.

[0047] As Figure 1 shown, the pressure plate 87 is installed at the end of the housing 80 on the Y - direction side. The material of the pressure plate 87 is metal or the like. As Figure 3As shown, on the surface of the pressing plate 87 on the Y+ direction side, there is a protrusion 87a for pressing the end plate 78 of each battery laminate Bs in the Y+ direction through the pressing window 82.

[0048] As Figure 1 shown, the port component 85 is installed at the end of the housing 80 on the X- direction side. The port component 85 is provided with a power port 85a. Inside the power port 85a, there are the positive terminal and the negative terminal of the entire battery pack 100.

[0049] Each battery cell 70 has a positive electrode p at one end in the X direction on the upper surface of the outer package, and a negative electrode n at the other end in the X direction on the upper surface of the outer package. Specifically, for a specified plurality of battery cells 70, the positive electrode p is arranged on the X- direction side, and the negative electrode n is arranged on the X+ direction side. On the other hand, for the battery cells 70 other than these, the negative electrode n is arranged on the X- direction side, and the positive electrode p is arranged on the X+ direction side.

[0050] Most of the busbars 50 electrically connect the electrodes p and n of the battery cells 70 adjacent to each other in the X direction or the Y direction. On the other hand, a specified one busbar 50 electrically connects the positive electrode p of the battery cell 70 on the most positive side to the positive electrode of the entire battery pack 100 located inside the power port 85a. In addition, another busbar 50 electrically connects the negative electrode n of the battery cell 70 on the most negative side to the negative electrode of the entire battery pack 100 located inside the power port 85a. Through the above, in this embodiment, all the battery cells 70 in the battery pack 100 are connected in series.

[0051] Hereinafter, as Figure 5 shown, for each battery cell 70, the end face on the X direction side is called the "side face 70s", and the lower surface is called the "bottom face 70b". Each battery cell 70 has a curved surface 70c connecting the side face 70s and the bottom face 70b.

[0052] As Figure 2 shown, the battery pack 100 further includes a plurality of heat conducting sheets 75. Specifically, a heat conducting sheet 75 is provided on each battery cell 70. Each heat conducting sheet 75 is a rectangle with the X direction as the length direction and the Y direction as the width direction. As Figure 5 shown, each heat conducting sheet 75 has a heat conducting layer 75a on the upper side and a sliding layer 75b on the lower side. The materials of the heat conducting layer 75a and the sliding layer 75b are different resins, etc. Both the heat conducting layer 75a and the sliding layer 75b have electrical insulation and heat conductivity. The friction coefficient of the sliding layer 75b is smaller than that of the heat conducting layer 75a. More specifically, in this embodiment, the sliding layer 75b is a polyethylene terephthalate film. The upper surface of each heat conducting sheet 75 is mounted on the battery cell 70 so as to cover the part including the bottom face 70b and the curved surface 70c.

[0053] With the above, as Figure 4 shown, each heat conducting sheet 75 is disposed between the bottom surface of the battery cell 70 and the inner bottom surface 80i of the housing 80. And, the sliding layer 75b of each heat conducting sheet 75 abuts against the inner bottom surface 80i of the housing 80.

[0054] Hereinafter, as Figure 5 shown, the state formed by the heat conducting sheet 75 when no external force is applied to the heat conducting sheet 75 is defined as the "sheet natural state". As Figure 6 shown, assuming the sheet natural state, two battery laminates Bs are arranged in such a manner that the heat conducting sheets 75 adjacent to each other in the X direction overlap each other. However, in reality, since the heat conducting sheets 75 adjacent to each other in the X direction cannot overlap each other, elastic deformation occurs due to mutual abutment. According to the settings such as the thickness and elastic modulus of these heat conducting sheets 75, the specific arrangement in the X direction on the two battery laminates Bs is adjusted.

[0055] Hereinafter, as Figure 6 shown, the region where the heat conducting sheets 75 arranged along the X direction overlap each other assuming the sheet natural state is defined as the "overlap region R1". In addition, the region formed below the overlap region R1, that is, the region surrounded by the two heat conducting sheets 75 arranged along the X direction and the inner bottom surface 80i of the housing 80 assuming the sheet natural state is defined as the "gap region R2".

[0056] When viewed from the Y direction, the two battery laminates Bs are arranged such that the area of the overlap region R1 is less than or equal to the area of the gap region R2.

[0057] Next, the manufacturing steps of the battery pack 100 described above will be described. First, each heat conducting sheet 75 as Figure 2 shown is installed on the lower surface of the respective corresponding battery cell 70 as Figure 3 shown. Next, the two battery laminates Bs including these battery cells 70 are accommodated in the housing 80 arranged along the X direction. Next, as Figure 4 shown, the end plate 78 is pressed in the Y+ direction by the protrusion 87a of the pressing plate 87, and each battery laminate Bs is compressed in the Y direction. In this state, as Figure 1 shown, the pressing plate 87 is fixed to the housing 80. Thereafter, after the bus bar 50 is installed on each battery cell 70, a cover body (not shown) is installed at the upper end portion of the housing 80.

[0058] The configuration and effects of the present embodiment are summarized below.

[0059] According to the present embodiment, as Figure 4As shown, the sliding layer 75b of the heat-conducting sheet 75 abuts against the inner bottom surface 80i of the housing 80. The coefficient of friction of this sliding layer 75b is less than that of the heat-conducting layer 75a. Moreover, the heat-conducting sheet 75 is mounted on each battery cell 70 with respect to the bottom surface 70b of the battery cell 70 rather than the inner bottom surface 80i of the housing 80. Therefore, it is possible to suppress the drawback that a recess is formed on the heat-conducting sheet 75 due to the weight of the battery cell 70 and the bottom of the battery cell 70 is embedded in the recess. By the above, the battery cell 70 can slide easily within the housing 80.

[0060] Therefore, during the manufacturing process of the battery pack 100, when the battery laminate Bs is compressed in the Y direction, each battery cell 70 can slide smoothly in the Y direction. In addition, during subsequent use of the battery pack 100, due to the thermal expansion difference between the battery cells 70, etc., when each battery cell 70 slides in the Y direction within the housing 80, the sliding becomes smooth.

[0061] Moreover, as Figure 5 shown, each heat-conducting sheet 75 is mounted on the battery cell 70 in such a way as to cover not only the bottom surface 70b of the battery cell 70 but also the curved surface 70c. Thus, as Figure 6 shown, the end portion 75e in the X direction of each heat-conducting sheet 75 is mounted on the curved surface 70c or the side surface 70s of the battery cell 70, and it is not easy to generate friction with respect to the inner bottom surface 80i of the housing 80. Therefore, it is possible to suppress the drawback that the heat-conducting sheet 75 peels off from the end portion 75e in the X direction. Thus, it is possible to suppress the peeling of the heat-conducting sheet 75.

[0062] As Figure 6 shown, assuming the natural state of the sheet, two battery laminates Bs are arranged in such a way that the heat-conducting sheets 75 adjacent to each other in the X direction overlap each other. As Figure 7 shown, due to this overlap, the heat-conducting sheet 75 undergoes elastic deformation, and a part of the heat-conducting sheet 75 protrudes into the gap region R2 located below the overlap region R1. Thus, it is possible to reduce the gap in the gap region R2 and improve the heat-conducting performance from the battery cell 70 to the bottom of the housing 80.

[0063] As Figure 6 shown, when viewed from the Y direction, the two battery laminates Bs are arranged in such a way that the area of the overlap region R1 is less than or equal to the area of the gap region R2. Therefore, as Figure 7 shown, when the heat-conducting sheet 75 undergoes elastic deformation due to this overlap, the protruding portion of the heat-conducting sheet 75 generated due to this elastic deformation is received within the gap region R2. Therefore, it is possible to suppress the drawback that the protruding portion of the heat-conducting sheet 75 has nowhere to go and protrudes downward, etc. Thus, it is possible to suppress the drawback that hinders the sliding of the battery cell 70 with respect to the inner bottom surface 80i of the housing 80. Therefore, it is possible to ensure the slidability of the battery cell 70 with respect to the inner bottom surface 80i of the housing 80.

[0064] As shown Figure 5 The sliding layer 75b of the heat conducting sheet 75 shown has a polyethylene terephthalate film. The polyethylene terephthalate film is excellent in both low friction property and insulation property. Therefore, for the sliding layer 75b of the heat conducting sheet 75, both low friction property and insulation property can be ensured simultaneously.

[0065] [Other embodiments]

[0066] The above - shown embodiments can be changed in the following ways, for example. Figure 1 The shown housing 80 can accommodate only one battery laminate Bs, or can accommodate three or more battery laminates Bs. In the housing 80, a plurality of arranged connectors may be connected in series, and the arranged connectors have a specified number of battery cells 70 such as two or three.

[0067] Figure 5 The shown sliding layer 75b can also be made of a material other than the polyethylene terephthalate film. Even when Figure 6 the area of the shown overlapping region R1 exceeds the area of the gap region R2, and in cases where the possibility of hindering the sliding of the battery cell 70 is relatively small, etc., the area of the overlapping region R1 can also exceed the area of the gap region R2. In cases where the heat conduction performance from the battery cell 70 to the bottom of the housing 80 can be sufficiently ensured even when the heat conducting sheets 75 do not overlap with each other in the natural state, etc., two battery laminates Bs can also be arranged in a non - overlapping manner.

[0068] Reference numerals

[0069] 70 Battery cell

[0070] 70s Side surface of the battery cell

[0071] 70b Bottom surface of the battery cell

[0072] 70c Curved surface of the battery cell

[0073] 75 Heat conducting sheet

[0074] 75a Heat conducting layer

[0075] 75b Sliding layer

[0076] 80 Housing

[0077] 80i Inner bottom surface of the housing

[0078] 100 Battery pack

[0079] Bs Battery laminate

[0080] R1 Overlapping region

[0081] R2 clearance area

[0082] X width direction

[0083] Y stacking direction

Claims

1. A battery pack, comprising: a plurality of battery cells; and a housing that houses a battery stack in which the battery cells are stacked in a predetermined stacking direction; Each of the battery cells has a curved surface that connects a side surface and a bottom surface on a width direction side orthogonal to the stacking direction; Among them, Each of the battery cells is provided with a heat conducting sheet, Each of the heat conducting sheets has a heat conducting layer and a sliding layer with a friction coefficient smaller than that of the heat conducting layer, The surface on the heat conducting layer side of each of the heat conducting sheets is mounted on the battery cell so as to cover a part including the bottom surface and the curved surface in the battery cell, The sliding layer abuts against the inner bottom surface of the housing.

2. The battery pack according to claim 1, Among them, The housing houses a plurality of the battery stacks side by side in the width direction, The state formed by the heat conducting sheet when no external force is applied to the heat conducting sheet is defined as the natural state of the sheet, Assuming the natural state of the sheet, a plurality of the battery stacks are arranged in such a manner that the heat conducting sheets adjacent to each other in the width direction overlap each other.

3. The battery pack according to claim 2, Among them, The region where the heat conducting sheets arranged in the width direction overlap each other assuming the natural state of the sheet is defined as the overlapping region, The region formed below the overlapping region, that is, the region surrounded by two of the heat conducting sheets arranged in the width direction and the inner bottom surface assuming the natural state of the sheet, is defined as the gap region, When viewed from the stacking direction, a plurality of the battery stacks are arranged in such a manner that the area of the overlapping region is equal to or less than the area of the gap region.

4. The battery pack according to any one of claims 1 to 3, Among them, The sliding layer is a polyethylene terephthalate film.

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