Layered Positive Electrode Composition for High-Density Battery Output
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face a challenge in achieving both high filling density of the positive electrode mixture layer and excellent output characteristics, as increased filling density typically leads to deterioration of output characteristics.
Innovation Solution
A positive electrode with a double-layer structure, where the first layer contains non-aggregated lithium-containing transition metal composite oxide particles (>80% by mass) and the second layer contains secondary particles formed by aggregation of primary particles, improves output characteristics while maintaining high filling density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the filling density of the positive electrode mixture layer is increased to increase battery capacity, then the capacity is improved, but the output characteristics deteriorate
Solution Approach 1:
The positive electrode mixture layer is divided into two distinct layers: a first layer containing non-aggregated particles (≥80 mass%) for excellent output characteristics, and a second layer containing secondary particles for high filling density. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between output characteristics and capacity.
Solution Approach 2:
Different regions of the positive electrode mixture layer are assigned different particle compositions tailored to local requirements. The first layer (closer to current collector) uses non-aggregated particles for superior electron conduction and output, while the second layer (outer layer) uses secondary particles to maximize capacity through higher filling density. Each layer's composition is optimized for its specific position and function.
Data Source
AI summary
A nonaqueous electrolyte secondary battery positive electrode comprises a positive electrode mixture layer that contains, as positive electrode active materials, first lithium-containing transition metal composite oxide particles, which are non-aggregated particles having a volume-based median diameter of 2-10 μm, and second lithium-containing transition metal composite oxide particles, which are secondary particles having a volume-based median diameter of 10-30 μm and formed by the agglomeration of primary particles having an average particle diameter of 50 nm-2 μm, and that has a first layer formed on the positive electrode core material side and a second layer formed on the first layer. The first layer contains at least the first composite oxide particles, and the content of said composite oxide particles is 80% or more relative to the total mass of the positive electrode active materials contained in the first layer. The second layer contains at least the second composite oxide particles.