Wound Battery Electrode Structure for Crack-Resistant Start Regions
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Solution Overview
Problem
The electrode material on the outer peripheral side of conventional non-aqueous electrolyte secondary batteries is unevenly distributed, leading to increased breakage and cracking at the winding-start side where the curvature is large due to charge and discharge cycles.
Innovation Solution
A winding-type electrode body design where the first and second electrodes are wound together with a separator, featuring uniform or increasing mixture layer amounts per unit length in specific regions to minimize breakage and damage, particularly at the winding-start side with high curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the electrode material amount is maximized on the winding-start side to increase battery capacity, then the battery capacity is improved, but the electrode material is easily broken and cracked due to large curvature and extension/contraction during charge and discharge
Solution Approach 1:
The patent applies local quality by making the electrode mixture layer thickness non-uniform along the winding direction. Specifically, the thickness is decreased from the winding-start side toward the winding-finish side, with the reduction rate being greater near the winding-start side. This creates a gradient structure where the electrode material distribution is optimized locally: thicker regions provide sufficient capacity while thinner regions near high-curvature areas reduce stress concentration and prevent breakage during charge-discharge cycles.
2Ease of manufacture
If the electrode material amount is uniformly distributed to simplify manufacturing, then the manufacturing process is simplified, but the electrode material on the outer peripheral side becomes excessive where curvature is large, leading to breakage and cracking
Solution Approach 1:
The patent applies parameter changes by modifying the thickness parameter of the electrode mixture layer along the winding direction. Instead of maintaining a constant thickness, the thickness parameter is varied continuously or gradually, with a greater reduction rate near the winding-start side and a smaller reduction rate toward the winding-finish side. This parameter variation optimizes the electrode structure to prevent breakage while remaining compatible with conventional manufacturing processes.
Data Source
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AI summary
In the present invention, a winding-start region that is closer to a winding-start side in the winding direction than a positive electrode core exposed part has positive electrode mixture unit amounts of a positive electrode inner mixture layer and a positive electrode outer mixture layer that are approximately uniform or increasing toward a winding-end side in the winding direction. A winding-start facing region, which faces the winding-start region across a separator, has negative electrode mixture unit amounts of a negative electrode inner mixture layer and a negative electrode outer mixture layer that are approximately uniform or increasing toward the winding-end side in the winding direction. The positive electrode inner mixture layer and the positive electrode outer mixture layer each have a positive electrode mixture unit amount that differs at two or more locations in the winding direction, excluding the positive electrode core exposed part. The negative electrode inner mixture layer and the negative electrode outer mixture each have a fluctuating part where the negative electrode mixture unit amount fluctuates toward the winding-end side in the winding direction.