Cathode Particle Gradient in Non-Aqueous Batteries for Capacity and Cycle Life
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Solution Overview
Problem
Existing non-aqueous electrolyte secondary batteries struggle to achieve high capacity and excellent storage characteristics and cycle characteristics simultaneously, with previous solutions focusing on improving cycle characteristics at the expense of battery capacity or vice versa.
Innovation Solution
A non-aqueous electrolyte secondary battery design that incorporates a positive electrode with a specific composition and structure, featuring a positive electrode core and a mixture layer with non-aggregated and secondary lithium-metal composite oxide particles. The non-aggregated particles have a median diameter of 2-10 μm, while the secondary particles have a median diameter of 10-30 μm. The content of non-aggregated particles is higher on the surface side than on the core side of the positive electrode mixture layer, and the non-aqueous electrolyte liquid contains a cyclic carbonate and a chain carbonate at a volume ratio of 3:7 to 6:4.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-aggregated particles are used as positive electrode active material, then cycle characteristics are improved, but battery capacity decreases due to decrease in filling property
Solution Approach 1:
The patent combines non-aggregated particles (2-10 μm) and secondary particles (10-30 μm) in a mixed structure within the positive electrode mixture layer. This merging of different particle types allows the non-aggregated particles to provide good cycle characteristics while the secondary particles improve filling density and battery capacity, thus resolving the contradiction between cycle life and capacity.
Solution Approach 2:
The patent creates a non-uniform distribution of particle types within the positive electrode mixture layer, where non-aggregated particles are concentrated in certain regions and secondary particles in others. This local differentiation allows different regions to contribute differently to overall performance, with non-aggregated particles providing structural stability for cycle life and secondary particles enhancing capacity through better packing.
2Quantity of substance
If high capacity is pursued, then storage characteristics and cycle characteristics cannot be achieved simultaneously
Solution Approach 1:
The patent optimizes specific parameters including particle size ranges (non-aggregated: 2-10 μm, secondary: 10-30 μm), particle size ratios, and electrolyte composition (cyclic carbonate to chain carbonate volume ratio of 3:7 to 6:4). These parameter optimizations enable the positive electrode to achieve high capacity while maintaining excellent storage characteristics through improved structural stability and electrolyte interaction.
3Reliability
If non-aggregated particles with specific size are used, then cycle characteristics improve, but filling density decreases
Solution Approach 1:
The patent creates a composite particle system combining non-aggregated particles (2-10 μm) and secondary particles (10-30 μm) with different structural characteristics. The non-aggregated particles provide structural integrity for cycle stability, while the secondary particles with their aggregated structure improve filling density through better packing efficiency, achieving both goals simultaneously.
Data Source
AI summary
In this non-aqueous electrolyte secondary battery: a non-aqueous electrolytic solution includes a cyclic carbonate and a linear carbonate in a 3:7 to 6:4 volume ratio; a positive electrode mixture layer includes first lithium metal composite oxide particles being non-aggregated particles having a median diameter of 2 to 10 μm on a volume basis and second lithium metal composite oxide particles being secondary particles having a median diameter of 10 to 30 μm on a volume basis and formed by the aggregation of primary particles having an average particle diameter of 50 nm to 2 μm; when the positive electrode mixture layer is divided into two equal regions in the thickness direction and the regions are defined as a first region and a second region sequentially from the surface side, the content of the first lithium metal composite oxide particles is higher in the first region than in the second region.