Wound Battery Negative Electrode Layout for Core Circularity
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face deformation of electrode plates where positive and negative electrodes face each other due to expansion during charge-discharge cycles, affecting the circularity of the winding core portion.
Innovation Solution
Incorporating a non-facing portion in the negative electrode that does not face the positive electrode, with a mixture non-facing portion having an average surface distance of at least 90 μm and a core material non-facing portion, to maintain the circularity of the winding core portion and reduce stress on the electrode assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electrode assembly expands during charge-discharge cycles, then the battery can store and release energy, but stress is locally applied to the central portion causing electrode plate deformation
Solution Approach 1:
The negative electrode is divided into two functional regions: a facing portion that faces the positive electrode for energy storage and release, and a non-facing portion that does not face the positive electrode to absorb expansion stress. This segmentation allows the electrode to simultaneously perform energy functions and stress accommodation, preventing electrode plate deformation while maintaining charge-discharge capability.
2Reliability
If a non-facing portion is added to maintain circularity and reduce stress, then structural integrity is improved, but the device complexity increases
Solution Approach 1:
The non-facing portion is specifically positioned at the central portion of the negative electrode where stress concentration occurs during expansion. By applying this structural modification locally rather than uniformly across the entire electrode, the design maintains simplicity in most areas while providing targeted stress relief where needed, thus improving reliability without significantly increasing overall device complexity.
Data Source
AI summary
A secondary battery comprises: an electrode body obtained by winding a negative electrode in which a negative electrode mixture layer is formed on a negative electrode core body and a positive electrode. The secondary battery is characterized in that: the negative electrode has, at the winding direction inner-end side of the electrode body, a non-facing part which does not face the positive electrode with the separator therebetween; the non-facing part has a mixture non-facing part in which the negative electrode mixture layer is formed on at least one surface of the negative electrode core body, from the winding direction outer end of the non-facing part and toward the winding direction inner side; and the average value of a mixture surface distance which is between the mixture non-facing part and the negative electrode positioned one turn outward of the mixture non-facing part is not less than 90 μm.