Battery pack

Abstract

The utility model relates to a battery pack which is provided with a laminated body formed by alternately laminating a plurality of single batteries and a plurality of heat insulation materials, each single battery is provided with a shell for accommodating a winding body and an external film arranged on the outer surface of the shell, and the heat insulation materials are in contact with the side surface of the external film in the laminating direction of the laminated body. At least one of the case, the exterior film, and the heat insulating material is formed such that the thickness of a portion on the end side of the wound body is greater than the thickness of a portion on the center side of the wound body. This makes it possible to suppress the occurrence of lithium deposition at the end of the wound body of the single cell.

Description

Technical Field

[0001] The utility model relates to a battery pack. Background Art

[0002] Patent Document 1 discloses a structure in which a portion of a separator's terminal end portion that is not fixed by a roll-stop tape is partially bent in order to suppress lithium deposition in a single cell.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2021-68553

[0004] However, the structure described in Patent Document 1 is a structure for suppressing lithium precipitation caused by the stopper tape, and is not a countermeasure for lithium precipitation at the end of the winding body. When the winding body is manufactured, coating sag occurs at the end of the winding body. Therefore, the inter-electrode distance between the positive electrode and the negative electrode widens due to coating sag at the end of the winding body, and the local resistance increases, so lithium precipitation may easily occur. Utility Model Content

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

[0006] The battery pack of the utility model has a stacked body formed by alternately stacking a plurality of single cells and a plurality of insulating materials, wherein the single cells have a shell for accommodating a winding body and an outer film arranged on the outer surface of the shell, the insulating material is in contact with the side surface of the outer film in the stacking direction of the stacked body, and at least any one of the shell, the outer film and the insulating material is formed such that the thickness of a portion on the end side of the winding body is greater than the thickness of a portion on the central side of the winding body.

[0007] According to the present invention, it is possible to suppress the occurrence of lithium deposition at the end of the wound body of the single cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Schematic diagram showing a battery pack in an embodiment.

[0009] Figure 2 This is a diagram for explaining a structure in which the thickness of the case is increased on the end side of the wound body.

[0010] Figure 3 This is a diagram for explaining a structure in which the thickness of the exterior film is increased on the end side of the wound body.

[0011] Figure 4 This is a diagram for explaining a structure in which the thickness of the heat insulating material is increased on the end side of the wound body. DETAILED DESCRIPTION

[0012] The battery pack in the embodiment of the present invention will be described in detail below. In addition, the present invention is not limited to the embodiment described below.

[0013] Figure 1 Schematic diagram of a battery pack in an embodiment. The battery pack 1 includes a plurality of cells 10 and a plurality of insulating materials 20. The battery pack 1 includes a stack 2 in which the cells 10 and the insulating materials 20 are alternately stacked. The insulating material 20 is a spacer disposed between adjacent cells 10. Furthermore, the battery pack 1 includes a pair of end plates disposed at both end sides of the stack 2 in the stacking direction and a restraining member installed in a manner connecting the pair of end plates. In the battery pack 1, a restraining pressure in the stacking direction is applied to the stack 2 by a pair of end plates and a restraining member. The restraining pressure acts on the stack 2 from both end sides in the stacking direction toward the center side in the stacking direction. The stack 2 is held as a whole by the restraining pressure. The stacking direction of the stack 2 coincides with the X direction, and the width direction of the stack 2 coincides with the Y direction.

[0014] The cell 10 is a lithium ion secondary battery and includes a wound body 11 , a case 12 , and an exterior film 13 .

[0015] 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 formed by winding a laminated body in which the positive electrode sheet and the negative electrode sheet are laminated with the separator interposed therebetween.

[0016] The positive electrode sheet of the winding body 11 has a positive electrode collector and a positive electrode active material layer. The positive electrode collector is an electrode substrate formed into a long strip of foil. The positive electrode active material layer is respectively provided on two opposite surfaces of the positive electrode collector. The positive electrode collector has an uncoated portion on the positive electrode side at one end in the width direction where the positive electrode active material layer is not formed and the positive electrode collector is exposed. The positive electrode active material layer has coating sags formed at both ends in the width direction.

[0017] The negative electrode sheet of the winding body 11 has a negative electrode collector and a negative electrode active material layer. The negative electrode collector is an electrode substrate formed into a long strip of foil. The negative electrode active material layer is respectively provided on two opposite surfaces of the negative electrode collector. The negative electrode collector has an uncoated portion on the negative electrode side at one end in the width direction where the negative electrode active material layer is not formed and the negative electrode collector is exposed. The negative electrode active material layer has coating sags formed at both ends in the width direction.

[0018] In the wound body 11, the positive electrode sheet, the negative electrode sheet and the separator are stacked in a manner that their respective length directions are consistent. The stacked body before winding is stacked 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 stacked with the separator interposed therebetween are wound around its strip-shaped axis extending in the width direction.

[0019] The shell 12 is a can that accommodates the winding body 11. The shell 12 is made of a metal such as aluminum or an aluminum alloy. The shell 12 is formed into a flat rectangular parallelepiped shape and has side wall portions 12a facing each other in the stacking direction of the stack 2. The side wall portion 12a is a wall portion that receives the restraining pressure. The side wall portion 12a has a flat surface 12c that is pressed from the insulating material 20 in the state of the battery pack 1, and an inner surface 12b that faces the flat surface of the winding body 11 in the stacking direction of the stack 2.

[0020] The exterior film 13 is a film covering the outer surface of the housing 12. The exterior film 13 has a side portion 13a sandwiched by the housing 12 and the heat insulating material 20 in the stacking direction of the stacked body 2. The side portion 13a has an inner side surface 13b in contact with the flat surface 12c of the housing 12 and an outer side surface 13c in contact with the side surface 20a of the heat insulating material 20.

[0021] In the single cell 10 constructed in this way, when manufacturing the wound body 11, paint sag occurs at the end 11a of the wound body 11. At the end 11a of the wound body 11, the inter-electrode distance between the positive electrode and the negative electrode becomes larger due to the paint sag, so that the resistance increases and lithium is easily precipitated. The inter-electrode distance is the distance in the stacking direction of the stacked positive electrode sheet, separator and negative electrode sheet 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 battery pack 1, in order to suppress the lithium precipitation at the end 11a of the wound body 11 caused by paint sag, it is constructed so that the inter-electrode distance in the wound body 11 can be constant.

[0022] Specifically, for the structural parts of the battery pack 1, the thickness of the part where the restraining pressure acts on the wound body 11 is made adjustable, and the part on the end 11a side of the wound body 11 is made thicker than the part on the central part side of the wound body 11. As a result, in the state of the battery pack 1, the restraining load (end load) acting on the end 11a of the wound body 11 by the restraining pressure in the stacking direction acting on the stacked body 2 can be made larger than the restraining load (central load) acting on the central part of the wound body 11. This can increase the end load, reduce the inter-electrode distance on the end 11a side where the paint sags, and thus make the inter-electrode distance in the wound body 11 uniform.

[0023] The structural components that exert restraining pressure on the wound body 11 in the stacked body 2 include the case 12, the outer film 13, and the heat insulating material 20. In the battery pack 1, at least one of the case 12, the outer film 13, and the heat insulating material 20 is relatively thickened at the end 11a side of the wound body 11. This makes it possible to selectively increase the end load.

[0024] like Figure 2As shown, in the structure of making the housing 12 thicker, the outer side of the side wall 12a in the width direction is formed thicker than the center side in the width direction. The outer surface of the side wall 12a is formed as a flat surface 12c, and the inner surface 12b is formed as a curved surface curved relative to the width direction.

[0025] like Figure 3 As shown, in the structure of making the outer film 13 thicker, the outer side of the side portion 13a in the width direction is formed thicker than the center side in the width direction. The inner side surface 13b of the side portion 13a is formed as a flat surface, and the outer side surface 13c of the side portion 13a is formed as a curved surface curved relative to the width direction.

[0026] like Figure 4 As shown, in the structure where the insulating material 20 is thickened, the outer portions in the width direction of the insulating material 20 are formed thicker than the central portions in the width direction. The side surfaces 20a on both sides in the stacking direction of the insulating material 20 are formed as curved surfaces curved relative to the width direction.

[0027] As described above, according to the embodiment, the inter-electrode distance in the wound body 11 can be made constant by increasing the thickness of at least one of the case 12, the outer film 13, and the heat insulating material 20 on the end 11a side of the wound body 11. This can suppress the occurrence of lithium deposition at the end 11a of the wound body 11.

Claims

1. A battery pack comprising a stacked body formed by alternately stacking a plurality of single cells and a plurality of thermal insulation materials, characterized in that: The single cell includes a case for housing the wound body and an exterior film disposed on an outer surface of the case. The heat insulating material is in contact with the side surface of the exterior film in the stacking direction of the stacked body, At least any one of the case, the exterior film, and the heat insulating material is configured such that a thickness of a portion on an end portion side of the wound body is greater than a thickness of a portion on a center portion side of the wound body.

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