Boron-Gradient High-Nickel Cathode for Battery Stability
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Solution Overview
Problem
Lithium-transition metal composite oxides with high Ni content in non-aqueous electrolyte secondary batteries face challenges in maintaining battery capacity and resistance at high temperatures due to particle cracking and secondary reactions with the electrolyte, which degrades the cycle and rate characteristics.
Innovation Solution
A positive electrode active material with a lithium-transition metal composite oxide containing nickel in excess of 80 mol% and boron on the particle surface, where the boron coverage ratio is higher on larger particles to inhibit cracking and secondary reactions, while minimizing resistance on smaller particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a boron compound is provided on the particle surface of the positive electrode active material to inhibit secondary reaction with the electrolyte, then the high-temperature cycle characteristic is improved, but the rate characteristic degrades due to the formation of a resistance layer
Solution Approach 1:
The patent applies different boron coverage ratios to different particle size groups: larger particles (≥D70) have a boron coverage ratio of 80% or more to inhibit cracking and secondary reactions at high temperature, while smaller particles (≤D30) have a boron coverage ratio of 20% or less to minimize resistance layer formation. This local differentiation resolves the contradiction by optimizing boron coverage for each particle size's specific functional requirements.
2Stability of the object's composition
If the boron coverage ratio is increased to inhibit particle cracking, then the high-temperature cycle characteristic is improved, but the resistance increases due to the resistance layer
Solution Approach 1:
The patent differentiates boron coverage by particle size: large particles receive high boron coverage (≥80%) to prevent cracking and maintain structural stability, while small particles receive low boron coverage (≤20%) to minimize resistance. This local quality approach allows each particle size group to have optimized properties for its specific role.
Solution Approach 2:
The patent segments the particle population into three size groups (large: ≥D70, medium: D30-D70, small: ≤D30) and applies different boron coverage ratios to each segment. This segmentation enables targeted optimization where large particles are protected from cracking while small particles maintain low resistance, resolving the contradiction between stability and harmful resistance effects.
Data Source
AI summary
A positive electrode active material for a non-aqueous electrolyte secondary battery according to a configuration includes a lithium-transition metal composite oxide containing nickel (Ni) in an amount of greater than or equal to 80 mol %, in which boron (B) is present at least on a particle surface of the lithium-transition metal composite oxide. In the lithium-transition metal composite oxide, when particles having a larger particle size than a volume-based 70% particle size (D70) are first particles and particles having a smaller particle size than a volume-based 30% particle size (D30) are second particles, a coverage ratio of B on surfaces of the first particles is larger than a coverage ratio of B on surfaces of the second particles by 5% or greater.