O2 Cathode Active Material Composition for Higher Cycle Capacity
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Solution Overview
Problem
Lithium-transition metal composite oxides with an O2 structure face challenges of low capacity and low capacity maintenance rate in charge-discharge cycles compared to those with an O3 structure.
Innovation Solution
A positive electrode active material comprising a lithium-transition metal composite oxide with a specific composition and particle size distribution, represented by the formula Liα[LixMnyCozMe(1-x-y-z)]O2, where Me includes Ni, Fe, Ti, Bi, and Nb, and the oxide has a crystal structure of O2 with a particle size distribution having a first peak in small particle diameters and a second peak in large particle diameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If lithium-transition metal composite oxide with O2 structure is used as positive electrode active material, then voltage drop in charge-discharge cycle is suppressed, but battery capacity and capacity maintenance rate are low
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compositional parameters (x, y, z ratios of Li, Mn, Co, and additional metals) and structural parameters (particle size distribution with specific D10-D90 ranges, crystal structure) of the lithium-transition metal composite oxide to simultaneously achieve voltage stability and high capacity
Solution Approach 2:
The patent uses composite materials by combining multiple transition metals (Mn, Co, Ni/Fe/Ti/Bi/Nb) in specific ratios within the lithium-transition metal composite oxide structure, creating a material that exhibits both voltage stability and high capacity properties that individual metals cannot achieve alone
2Stability of the object's composition
If lithium-transition metal composite oxide with O2 structure is used, then voltage drop is suppressed, but capacity maintenance rate in charge-discharge cycle is low
Solution Approach 1:
The patent changes the structural parameters by controlling particle size distribution within specific ranges (D10: 3-7 μm, D50: 8-12 μm, D90: 13-17 μm) and compositional parameters to enhance both voltage stability and capacity maintenance rate simultaneously
Solution Approach 2:
The patent applies local quality by creating a specific particle size distribution where different particle size regions serve different functions, with smaller particles providing high surface area for reactions and larger particles providing structural stability, thereby improving capacity maintenance rate while maintaining voltage stability
Data Source
AI summary
The positive electrode active material for a secondary battery includes a lithium-transition metal composite oxide. The lithium-transition metal composite oxide is represented by the general formula Liα[LixMnyCozMe(1-x-y-z)]O2 (in the formula, Me is at least one selected from Ni, Fe, Ti, Bi, and Nb, 0.5<α<1, 0.05<x<0.25, 0.4<y<0.7, 0<z<0.25) and has a crystal structure of O2 structure. The particle size distribution of the lithium-transition metal composite oxide has a first peak on the small particle size side and a second peak on the large particle size side.