Battery pack

Abstract

To provide a battery pack capable of suppressing lithium deposition at an end of a single cell wound body.SOLUTION: A battery pack 1 includes a laminate 2 in which a plurality of single cells 10 and a plurality of heat insulation materials 20 are alternately laminated. The single cell 10 includes a case 12 for accommodating a wound body 11, and an exterior film 13 disposed on an outer surface of the case 12. The heat insulation material 20 is in contact with an outside surface 13c of the exterior film 13 in the lamination direction of the laminate 2, and relatively thickens a portion on an end 11a side of the wound body 11 with respect to at least one of the case 12, the exterior film 13, and the heat insulation material 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery pack.

Background Art

[0002] Patent Document 1 discloses a structure in which a part of a portion of the end of a separator that cannot be stopped by a winding tape is bent in order to suppress lithium precipitation in a single battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the configuration described in Patent Document 1 suppresses lithium precipitation caused by the winding tape and is not a countermeasure against the occurrence of lithium precipitation at the end of the wound body. When manufacturing the wound body, a coating sag occurs at the end of the wound body. Therefore, at the end of the wound body, the distance between the positive electrode and the negative electrode becomes wider due to the coating sag, and the resistance increases locally, so there is a risk that lithium is likely to precipitate.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a battery pack capable of suppressing the occurrence of lithium precipitation at the end of a wound body of a single battery.

Means for Solving the Problems

[0006] The present invention relates to a battery pack having a laminate in which a plurality of single cells and a plurality of heat insulating materials are alternately laminated. The single cell has a case that houses a wound body and an exterior film disposed on the outer surface of the case. The heat insulating material contacts the side surface of the exterior film in the lamination direction of the laminate, and at least one of the case, the exterior film, and the heat insulating material is made relatively thick at a portion on the end side of the wound body.

Effect of the Invention

[0007] In the present invention, it is possible to suppress the occurrence of lithium precipitation at the end of the wound body of the single cell.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the battery pack in the embodiment of the present invention will be specifically described. Note that the present invention is not limited to the embodiments described below.

[0010] FIG. 1 is a schematic diagram showing a battery pack according to an embodiment. The battery pack 1 includes a plurality of single cells 10 and a plurality of heat insulating materials 20. The battery pack 1 has a laminate 2 in which the single cells 10 and the heat insulating materials 20 are alternately laminated. The heat insulating material 20 is a spacer disposed between adjacent single cells 10. Further, the battery pack 1 includes a pair of end plates disposed on both end sides in the lamination direction of the laminate 2, and a restraining member attached so as to connect the pair of end plates. In the battery pack 1, a restraining pressure in the lamination direction is applied to the laminate 2 by the pair of end plates and the restraining member. A restraining pressure acts on the laminate 2 from both end sides in the lamination direction toward the center side in the lamination direction. By this restraining pressure, the laminate 2 is integrally held. The lamination direction of the laminate 2 coincides with the X direction, and the width direction of the laminate 2 coincides with the Y direction.

[0011] The single cell 10 is a lithium ion secondary battery. The single cell 10 includes a wound body 11, a case 12, and an exterior film 13.

[0012] The wound body 11 includes a strip-shaped positive electrode sheet, a strip-shaped negative electrode sheet, and a strip-shaped separator, and is a flat electrode body obtained by winding a laminate in which the positive electrode sheet and the negative electrode sheet are laminated with the separator interposed therebetween.

[0013] The positive electrode sheet of the wound body 11 includes a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector is a strip-shaped foil-like electrode base material formed in a long shape. The positive electrode active material layer is provided on each of two opposing surfaces of the positive electrode current collector. The positive electrode current collector includes a positive electrode side uncoated portion where the positive electrode current collector is exposed without the positive electrode active material layer being formed at one end in the width direction. The positive electrode active material layer has coating sag formed at both ends in the width direction.

[0014] The negative electrode sheet of the wound body 11 includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is a strip-shaped foil-like electrode base material formed in a long shape. The negative electrode active material layer is provided on each of two opposing surfaces of the negative electrode current collector. The negative electrode current collector includes a non-polar side uncoated portion where the negative electrode current collector is exposed without the negative electrode active material layer being formed at one end in the width direction. The negative electrode active material layer has coating sag formed at both ends in the width direction.

[0015] In the wound body 11, the positive electrode sheet, the negative electrode sheet, and the separator are laminated so as to coincide with the longitudinal direction of each. Before winding, the laminate is laminated in the thickness direction in the order of the positive electrode sheet, the separator, the negative electrode sheet, and the separator. The wound body 11 has a flat structure in which the positive electrode sheet and the negative electrode sheet laminated with the separator interposed therebetween are wound around an axis extending in the strip width direction.

[0016] The case 12 is a can that houses the wound body 11. The case 12 is made of a metal such as aluminum or an aluminum alloy. The case 12 is formed in a flat rectangular parallelepiped shape and has side wall portions 12a facing each other in the stacking direction of the laminate 2. The side wall portion 12a is a wall portion that receives a restraint pressure. The side wall portion 12a has a flat surface 12b pressed by the heat insulating material 20 in the state of the assembled battery 1 and an inner surface 12c facing the flat surface of the wound body 11 in the stacking direction of the laminate 2.

[0017] The exterior film 13 is a film that covers the outer surface of the case 12. The exterior film 13 has a side portion 13a sandwiched between the case 12 and the heat insulating material 20 in the stacking direction of the laminate 2. The side portion 13a has an inner surface 13b that contacts the flat surface 12b of the case 12 and an outer surface 13c that contacts the side surface 20a of the heat insulating material 20.

[0018] In the single battery 10 configured as described above, in manufacturing the wound body 11, a coating sag occurs at the end portion 11a of the wound body 11. At the end portion 11a of the wound body 11, the resistance increases due to an increase in the inter-pole distance between the positive electrode and the negative electrode due to the coating sag, and lithium is likely to precipitate. This inter-pole distance is the distance in the stacking direction in which the positive electrode sheet, the separator, and the negative electrode sheet are stacked in the wound body 11, and is the distance between the positive electrode active material layer and the negative electrode active material layer of the wound body 11. Therefore, in the assembled battery 1, in order to suppress lithium precipitation at the end portion 11a of the wound body 11 caused by the coating sag, the inter-pole distance in the wound body 11 is configured to be constant.

[0019] Specifically, regarding the components of the assembled battery 1, the thickness of the portion where a restraining pressure is applied to the wound body 11 is made variable, and the portion on the end portion 11a side of the wound body 11 is made thicker than the portion on the central portion side of the wound body 11. As a result, in the state of the assembled battery 1, due to the restraining pressure in the stacking direction acting on the stacked body 2, the restraining load (end portion load) acting on the end portion 11a of the wound body 11 can be made larger than the restraining load (central portion load) acting on the central portion of the wound body 11. Thereby, the end portion load can be increased, and the inter-pole distance on the end portion 11a side with coating sag can be narrowed, so that the inter-pole distance in the wound body 11 can be made uniform.

[0020] The components that apply a restraining pressure to the wound body 11 in the stacked body 2 include the case 12, the exterior film 13, and the heat insulating material 20. In the assembled battery 1, for at least one of the case 12, the exterior film 13, and the heat insulating material 20, the portion on the end portion 11a side of the wound body 11 is made relatively thick. Thereby, the end portion load can be selectively increased.

[0021] As shown in FIG. 2, in the structure where the case 12 is thickened, the portion on the outer side in the width direction of the side wall portion 12a is formed thicker than the portion on the central side in the width direction. The side wall portion 12a has an outer surface formed as a flat surface 12b and an inner surface 12c formed as a curved surface curved in the width direction.

[0022] As shown in FIG. 3, in the structure where the exterior film 13 is thickened, the portion on the outer side in the width direction of the side portion 13a is formed thicker than the portion on the central side in the width direction. The side portion 13a has an inner side surface 13b formed as a flat surface and an outer side surface 13c formed as a curved surface curved in the width direction.

[0023] As shown in FIG. 4, in the structure where the heat insulating material 20 is thickened, the portion on the outer side in the width direction of the heat insulating material 20 is formed thicker than the portion on the central side in the width direction. In the heat insulating material 20, both side surfaces 20a on both sides in the stacking direction are formed as curved surfaces curved in the width direction.

[0024] As described above, according to the embodiment, by increasing the thickness of at least one of the case 12, the exterior film 13, and the heat insulating material 20 on the end portion 11a side of the wound body 11, the distance between the electrodes in the wound body 11 can be made constant. Thereby, it is possible to suppress the occurrence of lithium precipitation at the end portion 11a of the wound body 11.

Explanation of Reference Numerals

[0025] 1 set of batteries 2 laminate 10 single cells 11 wound body 11a end portion 12 case 13 exterior film 20 heat insulating material

Claims

【Claim 1】 A battery pack having a laminate in which a plurality of single cells and a plurality of heat insulating materials are alternately laminated, wherein the single cell has a case for accommodating a wound body, and an exterior film disposed on the outer surface of the case, the heat insulating material contacts the side surface of the exterior film in the lamination direction of the laminate, and a portion on the end side of the wound body is made relatively thick for at least one of the case, the exterior film, and the heat insulating material. The battery pack is characterized by the above.

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