Dual-Particle Cathode Material to Limit Ni Dissolution
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Solution Overview
Problem
The increased specific surface area of positive electrode active materials in non-aqueous electrolyte secondary batteries leads to higher Ni dissolution, causing resistance increases and internal short circuits, which degrade battery performance.
Innovation Solution
A positive electrode active material comprising a combination of Ni-containing lithium composite oxides with different average particle sizes and Ti content, where one oxide has a smaller primary particle size and larger secondary particle size than the other, to prevent Ni dissolution while maintaining high capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the specific surface area of the positive electrode active material is extended by using two different positive electrode active materials with different average secondary particle sizes, then the packing density of the positive electrode mixture layer is enhanced and battery capacity is increased, but the amount of Ni dissolution increases causing resistance increase and internal short circuit
Solution Approach 1:
The patent applies local quality by creating a dual-particle-size system where small secondary particles (1-5 μm) provide high specific surface area for capacity, while large secondary particles (6-20 μm) provide structural stability. Each particle size performs a specialized function: small particles enhance capacity through increased surface area, while large particles prevent Ni dissolution through their stable structure, resolving the contradiction between capacity and reliability.
Solution Approach 2:
The patent uses composite materials by combining two types of Ni-containing lithium composite oxides with different particle size characteristics into a single positive electrode active material system. This composite approach allows the material to simultaneously achieve high specific surface area (from small particles) and structural stability (from large particles), preventing Ni dissolution while maintaining high capacity.
2Productivity
If the average primary particle size is reduced to increase specific surface area, then battery capacity is improved, but Ni dissolution increases leading to resistance increase and internal short circuit
Solution Approach 1:
The patent applies segmentation by dividing the positive electrode active material into two distinct particle size segments: small secondary particles (1-5 μm) that provide high specific surface area for capacity, and large secondary particles (6-20 μm) that provide structural stability. This segmentation allows each segment to perform its specialized function independently, preventing Ni dissolution while maintaining high capacity.
Solution Approach 2:
The patent uses parameter changes by precisely controlling the average primary particle size (0.5-2 μm) and average secondary particle size (1-20 μm) within specific ranges. By optimizing these particle size parameters, the material achieves high specific surface area for capacity while maintaining structural stability to prevent Ni dissolution, resolving the contradiction between capacity improvement and harmful Ni dissolution.
Data Source
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AI summary
This positive electrode active material for nonaqueous electrolyte secondary batteries includes a Ni-containing lithium composite oxide A and Ni-containing lithium composite oxide B. The Ni-containing lithium composite oxide A contains at least 55 mol% of Ni relative to the total number of mols of metal elements other than Li. The Ni-containing lithium composite oxide B contains Ti and Ni. The Ni content in the Ni-containing lithium composite oxide B is at least 55 mol% relative to the total number of mols of metal elements other than Ti and Li. The Ni-containing lithium composite oxide A and the Ni-containing lithium composite oxide B have a prescribed average first particle diameter and a prescribed average second particle diameter, respectively, and the ratio between the Ni-containing lithium composite oxide A and the Ni-containing lithium composite oxide B is, in mass ratio, 5:95-55:45. By using this positive electrode active material, a higher capacity nonaqueous electrolyte secondary battery can be provided that has suppressed occurrence of resistance increase and internal short circuits.