Positive Electrode Single-Particle Structure for Battery Cycle Durability
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in maintaining capacity and durability during charge and discharge cycles, with existing positive electrode active materials not adequately addressing durability improvements.
Innovation Solution
A positive electrode with a mixture layer composed of single particles having no grain boundaries, where larger particles are surrounded by smaller particles with a diameter no more than one-fifth of the larger particles, and the content of larger particles is between 3% and 30% of the total active material, enhancing durability and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive electrode active materials with secondary particles formed by aggregation of primary particles are used, then manufacturing is easier and device complexity is lower, but durability and capacity retention deteriorate during charge-discharge cycles
Solution Approach 1:
The positive electrode active material is segmented into single particles without grain boundaries, eliminating the hierarchical aggregation structure of conventional materials. This segmentation into uniform single particles improves durability by preventing capacity degradation while maintaining manufacturing feasibility through simplified particle synthesis processes.
Solution Approach 2:
The invention applies local quality by ensuring that each particle in the positive electrode active material is a single particle with uniform composition and no grain boundaries, rather than having varying structures throughout. This local uniformity throughout the entire particle population enhances durability and capacity retention.
2Reliability
If single particles with no grain boundary are used, then durability is improved, but manufacturing precision and particle size control become more difficult
Solution Approach 1:
The invention changes the particle size parameter distribution by specifying that particles with diameters of 3 μm or more constitute 70-95% of the total particle count. This parameter control ensures manufacturing precision while maintaining the single particle structure without grain boundaries, achieving both durability and manufacturability.
3Reliability
If particles with diameter of 3 μm or more constitute 70-95% of total particles, then capacity retention is improved, but surface area to volume ratio decreases
Solution Approach 1:
The invention optimizes the particle size parameter by setting the diameter threshold at 3 μm and controlling the percentage distribution (70-95%). This parameter selection achieves the dual benefit of improving cycle characteristics through larger single particles while maintaining sufficient total surface area for effective electrochemical reactions.
Data Source
AI summary
Provided is a positive electrode for a nonaqueous electrolyte secondary battery of one embodiment, wherein a positive electrode active substance is constituted of single particles having no grain boundary therein. The single particles include first single particles having a particle diameter of at least 4 μm, and second single particles having a particle diameter smaller than that of the first single particles. In a positive electrode mixture layer, the second single particles are disposed around the first single particles. The second single particle, among the second single particles disposed adjacent to the first single particles, with the smallest particle diameter has a particle diameter that is no more than ⅕ of the particle diameter of the first single particle adjacent to said second single particle. The first single particles account for 3-30% relative to the total number of the particles in the positive electrode active substance.