Negative Electrode Assembly With Bent Layer Against Collector Cracks
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Solution Overview
Problem
Secondary batteries experience performance deterioration due to disconnections in the negative electrode current collector caused by volume changes from repeated shrinkage and expansion of the positive electrode, leading to interrupted current flow and battery malfunction.
Innovation Solution
An electrode assembly with a disconnection preventing layer formed by horizontally bending an extended negative electrode current collector to maintain electrical connection, incorporating a non-coated part and a welded connection at the bent portion to bypass potential cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the positive electrode is made shorter than the negative electrode to accommodate volume changes, then the battery can handle expansion/contraction, but the negative electrode current collector experiences stress and cracks leading to disconnection
Solution Approach 1:
The negative electrode current collector is divided into two functional parts: a coated part with active material that contacts the positive electrode, and a non-coated extended part that serves as a flexible buffer zone. This segmentation allows the structure to accommodate volume changes in the coated region while the extended non-coated part absorbs stress without cracking, maintaining electrical connection reliability.
Solution Approach 2:
The negative electrode current collector is pre-formed with an extended non-coated part beyond the coated region before assembly. This preliminary structural preparation creates a built-in buffer zone that proactively absorbs expansion/contraction stresses, preventing cracks from developing in the coated region during battery operation.
2Adaptability or versatility
If the negative electrode current collector is extended beyond the positive electrode edge, then it can accommodate expansion, but the extended portion is vulnerable to disconnection
Solution Approach 1:
Different regions of the negative electrode current collector are given different properties: the coated part has active material for electrochemical function, while the extended non-coated part has enhanced flexibility and stress-absorption capability. This local differentiation allows the extended portion to accommodate expansion without compromising overall structural integrity.
Solution Approach 2:
The extended non-coated part of the current collector acts as a pre-positioned cushion or buffer zone between the rigid coated region and the battery housing. This beforehand cushioning absorbs expansion stresses before they can propagate to the coated region, preventing disconnection while maintaining structural integrity.
3Ease of manufacture
If the positive electrode edge is made thick (free-edge type), then manufacturing is simplified, but crack generation in the negative electrode increases
Solution Approach 1:
The harmful stress concentration effect at the positive electrode edge is neutralized by extracting or removing the positive electrode active material at the edge region, creating a non-coated buffer zone in the negative electrode. This extraction eliminates the source of stress concentration that would otherwise cause cracks, while maintaining manufacturing simplicity through the free-edge design.
Data Source
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AI summary
The present invention relates to an electrode assembly including: a positive electrode; a negative electrode; and a separator interposed between the positive electrode and the negative electrode, wherein the positive electrode includes a positive electrode active material layer formed on a positive electrode current collector, and the negative electrode includes a negative electrode active material layer formed on a negative electrode current collector, wherein a non-coated part is formed at an edge of the negative electrode current collector, and wherein a disconnection preventing layer is formed as the negative electrode current collector, which is extended to an external side of the non-coated part, is horizontally bent.