Battery Electrode Protective Layer Layout for Bending Stress Relief
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Solution Overview
Problem
Conventional non-aqueous electrolyte rechargeable batteries face stress concentration and load issues due to abrupt bending of connecting portions, which can lead to mechanical stress on metal foils and separators during the collective foiling process.
Innovation Solution
Incorporating an insulating protective layer with a thickness ratio between the outer and inner layers to manage bending moments and reduce load on the positive electrode base, separators, and the like, using boehmite and PVdF as insulator particles with a specific mass ratio, and adjusting the thickness of the inner insulating protective layer to ensure proper insulation and bending behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the distal ends of the connecting portions are aligned to each other and collectively foiled, then the battery structure is compact and efficient, but stress is concentrated on the bent portion causing load on metal foil and separators
Solution Approach 1:
The insulating protective layer is applied locally at the distal end of the positive electrode connecting portion where stress concentration occurs during collective foiling. This local reinforcement protects the metal foil and separators from excessive load without affecting other parts of the battery structure, thereby maintaining compact assembly while preventing mechanical failure.
Solution Approach 2:
The insulating protective layer is applied in advance to the positive electrode connecting portion before the collective foiling process. This pre-protection cushioning prevents stress concentration and mechanical damage to the metal foil and separators during the bending and foiling operation, ensuring structural integrity while maintaining production efficiency.
2Strength
If the insulating protective layer thickness is increased to reduce load on positive electrode base, then mechanical strength is enhanced, but battery volume increases
Solution Approach 1:
The insulating protective layer is applied only at the distal end of the positive electrode connecting portion where stress concentration occurs, rather than uniformly across the entire electrode. This localized application provides necessary mechanical strength protection while minimizing the additional volume introduced by the protective layer.
Solution Approach 2:
The insulating protective layer is applied with a thickness that is sufficient to protect against stress concentration at the critical distal end region, but not excessively thick throughout the entire electrode structure. This partial application provides adequate mechanical strength while controlling the overall volume increase of the battery.
Data Source
AI summary
A non-aqueous electrolyte rechargeable battery includes an electrode body, a negative electrode current collector, and a positive electrode current collector. The electrode body includes a stack of a negative electrode sheet, a positive electrode sheet, and a separator. The negative electrode sheet includes a negative electrode base, a negative electrode mixture layer, and a negative electrode connecting portion. The positive electrode sheet includes a positive electrode base, a positive electrode mixture layer, a positive electrode connecting portion, and an insulating protective layer. The insulating protective layer includes an outer insulating protective layer on a surface relatively far from the positive electrode current collector in a stacking direction of the electrode body and an inner insulating protective layer on a surface relatively close to the positive electrode current collector in the direction. The outer insulating protective layer has a larger thickness than the inner insulating protective layer.