EP-4738448-A1 - SECONDARY BATTERY

EP4738448A1EP 4738448 A1EP4738448 A1EP 4738448A1EP-4738448-A1

Abstract

A secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode and the negative electrode are wound with the separator therebetween. The positive electrode includes a band-shaped positive electrode current collector and a positive electrode mixture layer provided on the positive electrode current collector. The positive electrode includes a positive electrode edge portion that includes one edge of the positive electrode in the lateral direction, and a positive electrode main portion other than the positive electrode edge portion. The positive electrode edge portion includes one or more positive electrode current collector-exposed portions that are provided partially at respective positions along the longitudinal direction of the positive electrode current collector. The exposed portions do not include the positive electrode mixture layer from the one edge in the lateral direction to the positive electrode main portion. The positive electrode mixture layer contains a positive electrode active material and a binder. The binder contains a first resin in an amorphous state.

Inventors

OMAE, TAKANORI
UKA, Youichirou
KISHI, Takuma
YAMAMOTO, NORIHISA

Assignees

Panasonic Intellectual Property Management Co., Ltd.

Dates

Publication Date: 20260506
Application Date: 20240606

Claims (14)

A secondary battery comprising: a positive electrode; a negative electrode; an electrolyte; and a separator, wherein the positive electrode and the negative electrode are wound with the separator therebetween, the positive electrode includes a positive electrode current collector having a band shape, and a positive electrode mixture layer provided on the positive electrode current collector, the positive electrode includes a positive electrode edge portion that includes one edge of the positive electrode in a lateral direction, and a positive electrode main portion other than the positive electrode edge portion, the positive electrode edge portion includes one or more positive electrode current collector-exposed portions that are provided partially at respective positions along a longitudinal direction of the positive electrode current collector, the positive electrode current collector-exposed portions not including the positive electrode mixture layer from the one edge of the positive electrode in the lateral direction to the positive electrode main portion, the positive electrode mixture layer contains a positive electrode active material and a binder, and the binder contains a first resin in an amorphous state.
The secondary battery according to claim 1, wherein the binder further contains a second resin in a crystalline state.
The secondary battery according to claim 1 or 2, wherein the positive electrode edge portion includes the positive electrode current collector-exposed portions that are intermittently provided along the longitudinal direction of the positive electrode current collector.
The secondary battery according to claim 1 or 2, wherein a mass of the positive electrode mixture layer per unit area provided on a surface of the positive electrode current collector is 240 g/m 2 or more.
The secondary battery according to claim 1 or 2, wherein a mass of the positive electrode mixture layer per unit area provided on a surface of the positive electrode current collector is 260 g/m 2 or more.
The secondary battery according to claim 1 or 2, wherein a mass of the positive electrode mixture layer per unit area provided on a surface of the positive electrode current collector is 280 g/m 2 or more.
The secondary battery according to claim 1 or 2, wherein a mass of the positive electrode mixture layer per unit area provided on a surface of the positive electrode current collector is 280 g/m 2 or more and 350 g/m 2 or less.
The secondary battery according to claim 2, wherein the first resin is a non-fluoropolymer, and the second resin is a fluoropolymer.
The secondary battery according to claim 2, wherein the first resin is a non-fluoropolymer and the second resin is a polyvinylidene fluoride-based polymer.
The secondary battery according to claim 2, wherein the first resin is a rubber-based polymer, and the second resin is a polyvinylidene fluoride-based polymer.
The secondary battery according to claim 2, wherein the first resin is a nitrile-based polymer or a styrene-based polymer, and the second resin is a polyvinylidene fluoride-based polymer.
The secondary battery according to claim 1 or 2, wherein a ratio between a length of the positive electrode edge portion in the lateral direction and a length of the positive electrode main portion in the lateral direction is in a range of 1:12 to 1:6.
The secondary battery according to claim 1 or 2, wherein a sum of lengths of all the positive electrode current collector-exposed portions in the longitudinal direction of the positive electrode current collector is 1% to 20% of a length of the positive electrode current collector in the longitudinal direction.
The secondary battery according to claim 1 or 2, wherein given that L100 represents a length of the positive electrode current collector and n represents a number of the positive electrode current collector-exposed portions, distances between the positive electrode current collector-exposed portions adjacent to each other are 0.8 × L100/n to 1.2 × L100/n.

Description

[Technical Field] The present disclosure relates to a secondary battery. [Background Art] Patent Literature 1 proposes "a method of manufacturing an electrode sheet for use in a power storage device, including discharging a mixture slurry into discharge regions of a belt-like current collector that extend in the length direction of the current collector from discharge nozzles corresponding to the respective discharge regions to form a mixture layer on the current collector, wherein the discharge regions are arranged such that a part of each discharge region overlaps a part of another discharge region adjacent thereto when viewed in the length direction of the current collector to form an overlapping portion, the overlapping portion has a length of 8 mm or less in the width direction of the current collector, and the mixture slurry is intermittently discharged to form an uncoated portion on at least one of the discharge regions." Patent Literature 2 proposes "an electrode sheet for use in a power storage device, including: a current collector having a substantially rectangular planar shape; and an active material layer formed on at least one surface of the current collector, wherein the current collector includes an exposed portion in a partial region in the longitudinal direction and at an end portion of the partial region in the width direction, and an electrode lead is to be connected to the exposed portion, and wherein, in a region in which the active material layer is formed, the elastic modulus of a first region adjacent to the exposed portion in the width direction is larger than the elastic modulus of a second region adjacent the exposed portion and the first region in the longitudinal direction". [Citation List] [Patent Literature] [Patent Literature 1] Japanese Patent No. 6965162[Patent Literature 2] Japanese Patent No. 6821595 [Summary of Invention] [Technical Problem] According to Patent Literatures 1 and 2, a high-capacity electrode sheet can be obtained due to the uncoated portion (or the exposed portion) of the mixture layer being reduced. However, as the energy density of the electrode increases, the mass of the mixture layer per unit area provided on the surface of the current collector increases to increase the difference in toughness between the coated portion and the uncoated portion. In addition, when the positive electrode and the negative electrode are wound with a separator interposed therebetween, a difference in degree of bending arises between the coated portion and the uncoated portion of the mixture layer. Therefore, fractures of the electrode are likely to occur at the boundary between the coated portion and the uncoated portion of the mixture layer. [Solution to Problem] One aspect of the present disclosure relates to a secondary battery including: a positive electrode; a negative electrode; an electrolyte; and a separator, wherein the positive electrode and the negative electrode are wound with the separator therebetween, the positive electrode includes a positive electrode current collector having a band shape, and a positive electrode mixture layer provided on the positive electrode current collector, the positive electrode includes a positive electrode edge portion that includes one edge of the positive electrode in a lateral direction, and a positive electrode main portion other than the positive electrode edge portion, the positive electrode edge portion includes one or more positive electrode current collector-exposed portions that are provided partially at respective positions along a longitudinal direction of the positive electrode current collector, the positive electrode current collector-exposed portions not including the positive electrode mixture layer from the one edge of the positive electrode in the lateral direction to the positive electrode main portion, the positive electrode mixture layer contains a positive electrode active material and a binder, and the binder contains a first resin in an amorphous state. [Advantageous Effects of Invention] According to the present disclosure, fractures of a positive electrode of a secondary battery can be suppressed. While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings. [Brief Description of Drawings] [FIG. 1] FIG. 1 is a schematic cross-sectional view of a secondary battery according to an exemplary embodiment.[FIG. 2] FIG. 2 is a schematic plan view of a positive electrode according to an exemplary embodiment.[FIG. 3] FIG. 3 is a schematic plan view of a negative electrode according to an exemplary embodiment. [Description of Embodiments] Embodiments of the present disclosure are described below by way of examples, but the present disclosure is not limited to the