NCM Cathode Particle Gradient for Low-Cobalt Output Stability
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Solution Overview
Problem
Lithium cobalt oxide-based positive electrode active materials for lithium secondary batteries have poor thermal properties and high costs, limiting their use in medium and large-sized devices, and reducing cobalt content leads to decreased discharge capacity and output characteristics.
Innovation Solution
A lithium transition metal oxide with a composition represented by Formula Li1+aNixCoyMnzM1wO2, where the cobalt content is less than the manganese content, and at least one of nickel, cobalt, and manganese has a concentration gradient from the center to the surface of the particle, forming a secondary particle structure with a specific c-axis direction angle, improving structural stability and lithium mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cobalt content is reduced in lithium nickel cobalt manganese oxide, then cost is reduced, but discharge capacity and output characteristics are reduced
Solution Approach 1:
The patent applies local quality by creating a concentration gradient where nickel content varies from the center to the surface of the particle. The center region has high nickel content for high capacity, while the surface region has lower nickel and higher manganese content for structural stability and output characteristics, allowing reduced overall cobalt content while maintaining performance
Solution Approach 2:
The patent uses composite materials by combining lithium nickel cobalt manganese oxide with a specific crystal structure orientation (c-axis perpendicular to surface) and concentration gradient composition, creating a composite effect that maintains output characteristics with reduced cobalt content through the synergistic combination of multiple elements in specific proportions and distributions
2Quantity of substance
If lithium cobalt oxide is used for high energy density, then capacity characteristics are improved, but thermal stability is poor due to unstable crystal structure
Solution Approach 1:
The patent uses composite materials by combining lithium nickel cobalt manganese oxide with a specific crystal structure orientation (c-axis perpendicular to surface) and concentration gradient composition, creating a composite effect that maintains output characteristics with reduced cobalt content through the synergistic combination of multiple elements in specific proportions and distributions
Solution Approach 2:
The patent applies local quality by creating a concentration gradient where nickel content varies from the center to the surface of the particle. The center region has high nickel content for high capacity, while the surface region has lower nickel and higher manganese content for structural stability and output characteristics, allowing reduced overall cobalt content while maintaining performance
Data Source
AI summary
A positive electrode active material includes a lithium transition metal oxide, in which a cobalt content in the lithium transition metal oxide is less than a manganese content, wherein at least one of nickel, cobalt, and manganese in the lithium transition metal oxide has a concentration gradient that gradually changes from a center of a particle to a surface thereof, the positive electrode active material is in the form of a secondary particle formed by agglomeration of primary particles, and a ratio in which angles between c-axis directions, which are measured at at least 8 points on a surface of the positive electrode active material by TEM analysis, and a growth direction of the particle at the measuring point satisfy 85° to 95° is 60% or more.