# US 12,763,375 B2 · Secondary battery > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,763,375 B2 - Document ID: US12763375B2 - Status: Granted - Kind: B2 - Application number: 17/793,267 - Filed: 2021-01-06 - Published: 2023-02-09 - Granted: 2026-10-13 - Earliest claimed: 2020-01-23 - Assignees: Panasonic Energy Co., Ltd. - Applicants: SANYO Electric Co., Ltd. - Inventors: Yuki Nakai; Atsushi Kaiduka; Tatsuhiko Suzuki; Takaharu Morikawa - Web page: https://patentgrep.com/patent/US12763375B2 ## CPC - H01M 10/0587: of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators - H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY ## Abstract With respect to a secondary battery of one embodiment of the present invention, at least one of a positive electrode core body and a negative electrode core body is configured such that the tensile elongation in the central part in the width direction is higher than the tensile elongation in both end parts in the width direction. With respect to a secondary battery of another embodiment of the present invention, at least one of a positive electrode core body and a negative electrode core body is configured such that the number of crystal grains per unit area in the central part in the width direction is smaller than the number of crystal grains per unit area in both end parts in the width direction. ## Claims ### Claim 1 A secondary battery, comprising an electrode assembly including a belt-like positive electrode, a belt-like negative electrode, and a belt-like separator, wherein the positive electrode and the negative electrode are laminated via the separator in a thickness direction, the positive electrode includes a positive electrode core elongated in a longitudinal direction orthogonal to the thickness direction and to a width direction, and a positive electrode active material layer formed on a surface of the positive electrode core, the negative electrode includes a negative electrode core elongated in a longitudinal direction orthogonal to the thickness direction and to a width direction, and a negative electrode active material layer formed on a surface of the negative electrode core, and the negative electrode core exhibits varying tensile elongation percentages depending on locations in the width direction, measured on specimens each encompassing an entire dimension of the negative electrode core in the thickness direction, such that a first tensile elongation percentage at a center portion of the negative electrode core in the width direction is higher than a second tensile elongation percentage at both end portions of the negative electrode core in the width direction. ### Claim 2 (depends on 1) The secondary battery according to claim 1, wherein the first tensile elongation percentage is equal to or higher than 1.2 times of the second tensile elongation percentage. ### Claim 3 A secondary battery, comprising an electrode assembly including a belt-like positive electrode, a belt-like negative electrode, and a belt-like separator, wherein the positive electrode and the negative electrode are laminated via the separator in a thickness direction, the positive electrode includes a positive electrode core elongated in a longitudinal direction orthogonal to the thickness direction and to a width direction, and a positive electrode active material layer formed on a surface of the positive electrode core, the negative electrode includes a negative electrode core elongated in a longitudinal direction orthogonal to the thickness direction and to a width direction, and a negative electrode active material layer formed on a surface of the negative electrode core, and the negative electrode core exhibits varying numbers of crystal grains per unit area depending on locations in the width direction, measured on specimens located at a uniform height in the thickness direction, such that a first number of crystal grains per unit area at a center portion of the negative electrode core in the width direction is smaller than a second number of crystal grains per unit area at both end portions of the negative electrode core in the width direction. ### Claim 4 (depends on 3) The secondary battery according to claim 3, wherein the first number of the crystal grains per unit area is equal to or smaller than ½ of the second number of the crystal grains per unit area. ### Claim 5 (depends on 1) The secondary battery according to claim 1, wherein each of the center portion and both end portions extends across an entire length in the longitudinal direction of the negative electrode core, and the center portion encompasses 25% or less of an entire width in the width direction of the negative electrode core. ### Claim 6 (depends on 3) The secondary battery according to claim 3, wherein each of the center portion and both end portions extends across an entire length in the longitudinal direction of the negative electrode core, and the center portion encompasses 25% or less of an entire width in the width direction of the negative electrode core.