Layered Lithium Metal Oxide Cathode to Minimize Cation Mixing
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Solution Overview
Problem
Lithium secondary batteries suffer from reduced capacity and deteriorating cycle characteristics due to cation mixing in lithium metal composite oxides, which occurs during production and charging/discharging stages.
Innovation Solution
A lithium metal composite oxide with a layered structure, specific compositional formula Li[Li m (Ni (1-x-y) Co x M y ) 1-m ]O 2, controlled Me site occupancy, and defined diffraction peak ratios, along with optimized particle size and crystallinity, is developed to minimize cation mixing and volume change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal composite oxide is used as positive electrode active material, then battery capacity can be improved, but cation mixing occurs during production and charging/discharging stages causing capacity loss and performance deterioration
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compositional parameters (m, x, y) in the formula Li[Li m (Ni (1-x-y) Co x M y ) 1-m ]O 2, where -0.1≤m≤0.2, 0≤x≤0.5, and 0≤y≤0.5. This compositional optimization reduces cation mixing while maintaining high capacity, directly resolving the contradiction between improving battery capacity and ensuring cycle characteristics.
Solution Approach 2:
The patent uses composite materials by incorporating multiple elements (Ni, Co, M where M is one of Mn, Fe, Cu, Ti, Mg, Ca, Al, Zn, Sn, Zr, B, Si, Nb, W, Ta, Ba, S, or P) in specific proportions within the layered oxide structure. This multi-element composition suppresses cation mixing and improves both capacity and cycle stability simultaneously.
2Stability of the object's composition
If nickel ions migrate to lithium ion sites in crystal structure, then cation mixing occurs resulting in replacement of lithium ions, but this causes capacity loss and battery performance deterioration
Solution Approach 1:
The patent applies local quality by creating a specific local chemical environment around lithium sites through the addition of M elements and optimization of Ni:Co:M ratios. This local compositional control prevents nickel ion migration to lithium sites while maintaining high battery capacity, resolving the contradiction between crystal structure stability and battery capacity.
3Reliability
If volume change is reduced through controlled cation mixing, then cycle characteristics improve, but manufacturing complexity increases due to precise compositional control requirements
Solution Approach 1:
The patent defines specific parameter ranges (m: -0.1 to 0.2, x: 0 to 0.5, y: 0 to 0.5) that simultaneously achieve volume change reduction and improved cycle characteristics. By establishing these clear parameter boundaries, the patent simplifies the manufacturing process while maintaining high reliability, resolving the contradiction between cycle characteristics and manufacturing complexity.
Data Source
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AI summary
Provided are a lithium metal composite oxide, a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery and a lithium secondary battery that are capable of improving the initial discharge capacity and the cycle characteristics of a lithium secondary battery. The lithium metal composite oxide has a layered structure, and satisfies conditions (1), (2) and (3).