Positive Electrode Layer Structure for Battery Reliability
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Solution Overview
Problem
Existing secondary batteries face challenges in improving reliability, particularly in maintaining the integrity and performance of the positive electrode structure.
Innovation Solution
The positive electrode includes a current collector with a positive electrode active material layer that has a first thin part and a first thick part, where the ratio of the positive electrode binder to the active material is lower in the thin part compared to the thick part, enhancing structural stability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the positive electrode active material layer is made uniformly thick, then the manufacturing process is simple, but the structural integrity and reliability during winding and charging-discharging cycles deteriorates
Solution Approach 1:
The positive electrode active material layer is segmented into multiple regions with different thicknesses along the winding direction. Specifically, it includes a first region with a first thickness and a second region with a second thickness different from the first thickness. This segmentation allows the electrode to better accommodate winding stresses and maintain structural integrity during charging-discharging cycles, resolving the contradiction between structural integrity and manufacturing simplicity.
Solution Approach 2:
Different regions of the positive electrode active material layer are given different local properties through varying thickness. The first region and second region have different thicknesses tailored to their specific functional requirements and stress conditions during winding and operation. This local quality approach optimizes structural integrity in critical areas while maintaining overall electrode performance.
2Reliability
If the binder content is increased uniformly throughout the electrode, then the structural stability improves, but the energy density and electrochemical performance deteriorates
Solution Approach 1:
The binder content is distributed non-uniformly across different regions of the positive electrode active material layer. Each region (first region and second region) has a binder content optimized for its specific requirements. Regions experiencing higher mechanical stress during winding have increased binder content for structural stability, while other regions maintain lower binder content to maximize energy density and electrochemical performance. This local optimization resolves the contradiction between structural stability and energy density.
Solution Approach 2:
The binder-to-active material ratio is varied as a parameter across different regions of the electrode. By changing this compositional parameter locally rather than maintaining a uniform value throughout, the electrode achieves optimal structural stability in critical areas while preserving high energy density in active regions, thus resolving the contradiction between these two opposing requirements.
Data Source
AI summary
A positive electrode includes a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector extends in both a longitudinal direction and a width direction. The positive electrode active material layer includes a positive electrode active material and a positive electrode binder and is stacked on the positive electrode current collector. The positive electrode active material layer includes a first thin part and a first thick part. The first thick part has a thickness greater than a thickness of the first thin part and is adjacent to the first thin part in the longitudinal direction. A ratio of an abundance of the positive electrode binder to an abundance of the positive electrode active material in the first thin part is lower than that in the first thick part.