Positive Electrode Material Gradient for Cycle and Rate Balance
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Solution Overview
Problem
Lithium-ion batteries face challenges in achieving balanced cycle performance and rate performance due to limitations in particle size and nickel content, where increased nickel content improves capacity but deteriorates cycle performance, and small particle sizes enhance rate performance but compromise cycle stability.
Innovation Solution
A positive electrode active material with a secondary particle structure, where the outer part has a larger average particle size than the inner part, with a controlled ratio of 1.1≤G≤10, incorporating elements like W, Nb, or Mo in the inner part and Mg, Ti, or Zr near the surface, to enhance cycle stability and rate performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content is increased to improve capacity, then the battery capacity is improved, but the cycle performance deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core contains high nickel content (0.8-0.95) for high capacity, while the outer shell contains lower nickel content (0.6-0.8) for better stability. This spatial differentiation of composition allows simultaneous achievement of high capacity and good cycle performance, resolving the contradiction between quantity of substance and reliability.
2Speed
If particle size is reduced to enhance rate performance, then the rate performance is improved, but the cycle stability is compromised
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core contains high nickel content (0.8-0.95) for high capacity, while the outer shell contains lower nickel content (0.6-0.8) for better stability. This spatial differentiation of composition allows simultaneous achievement of high capacity and good cycle performance, resolving the contradiction between quantity of substance and reliability.
3Ease of manufacture
If uniform particle size is used throughout the electrode, then the manufacturing process is simplified, but the overall performance cannot be optimized
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core contains high nickel content (0.8-0.95) for high capacity, while the outer shell contains lower nickel content (0.6-0.8) for better stability. This spatial differentiation of composition allows simultaneous achievement of high capacity and good cycle performance, resolving the contradiction between quantity of substance and reliability.
Data Source
AI summary
A positive electrode active material, including: a secondary particle formed from a primary particle. The secondary particle includes an inner part and an outer part that wraps the inner part. A ratio of an average particle size of primary particles in the outer part to an average particle size of primary particles in the inner part is G, and 1.1≤G≤10. The outer part is a region from an interface of the secondary particle to a surface of the secondary particle, and the inner part is a region from the interface of the secondary particle to a center of the secondary particle. The positive electrode active material in this disclosure improves cycle performance while ensuring good rate performance.