Positive Electrode Thickness Rules for Fast-Charging Li-Ion Cells
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Solution Overview
Problem
Lithium-ion batteries face challenges in achieving fast-charge performance without compromising storage and cycle performance, as existing solutions often result in particle damage during cold-pressing, leading to defective electrode plates and performance issues.
Innovation Solution
The electrochemical device incorporates a positive electrode with a film layer and current collector, where the thickness of the film layer and current collector are optimized to satisfy specific relationships, and the positive active material includes primary and secondary particles, ensuring proper distribution and preventing particle crushing during cold-pressing, thereby enhancing fast-charge, storage, and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the film layer thickness is increased to improve fast-charge performance, then the storage performance and cycle performance deteriorate due to particle crushing during cold-pressing
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships between film layer thickness (Dl), current collector thickness (Dc), and particle diameter (Dv99). When primary particles constitute 20-100% of positive active material, Dl≥Dv99-Dc; when primary particles constitute 0-20%, Dl≥1.1Dv99. These parameter relationships prevent particle crushing during cold-pressing while maintaining fast-charge performance.
Solution Approach 2:
The patent applies local quality by differentiating the structural requirements based on the composition of positive active material. Two distinct structural configurations are specified: one for electrodes with predominantly primary particles (20-100%) and another for electrodes with predominantly secondary particles (0-20% primary particles). This allows optimization of local structural characteristics according to the specific particle composition.
2Manufacturing precision
If the film layer is made thicker to accommodate larger particles, then the manufacturing precision improves, but the device complexity increases
Solution Approach 1:
The patent simplifies device complexity by establishing clear parameter relationships that guide structural design. The formulas Dl≥Dv99-Dc and Dl≥1.1Dv99 provide straightforward design criteria that ensure uniform particle distribution without requiring complex multi-parameter optimization, thereby improving manufacturing precision while maintaining design simplicity.
Data Source
AI summary
An electrochemical device includes a positive electrode, the positive electrode includes a current collector and a film layer containing a positive active material. The film layer is disposed on at least one surface of the current collector. The positive active material includes a primary particle and/or a secondary particle. When a mass percent A of the primary particle in the positive active material based on a mass of the positive active material satisfies 20%≤A≤100%, the film layer, the positive active material, and the current collector satisfy: Dl≥Dv99−Dc; and, when a mass percent A′ of the primary particle in the positive active material based on the mass of the positive active material satisfies 0≤A′≤20%, the film layer, the positive active material, and the current collector satisfy: Dl≥1.1 Dv99.