Cathode Active Material Coatings for Low-Cobalt Cycle Life
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Solution Overview
Problem
The demand for large-sized, high-capacity, and high-energy-density rechargeable lithium batteries has increased, but the supply of cobalt, a rare and expensive metal, is limited, necessitating the development of positive electrode active materials that either exclude or significantly reduce cobalt content while maintaining high capacity and cycle-life characteristics.
Innovation Solution
A positive electrode active material is developed with core particles composed of lithium nickel-manganese-based composite oxide coated with an aluminium layer and a grain boundary coating containing cobalt, enhancing structural stability and reducing gas generation under high-voltage and high-temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cobalt-free or low-cobalt positive electrode active materials are used, then cost is reduced and supply security is improved, but cycle-life characteristics deteriorate
Solution Approach 1:
The patent applies beforehand cushioning by pre-coating the core particles with an aluminium oxide layer and grain boundary coating before battery assembly. This protective coating acts as a cushion that prevents direct contact between the high-nickel core material and the electrolyte, reducing side reactions and structural degradation during cycling. The coating serves as a buffer that maintains structural integrity over thousands of charge-discharge cycles, enabling long cycle-life characteristics in cobalt-free or low-cobalt materials
2Quantity of substance
If high-nickel lithium nickel-manganese-based composite oxide is used, then capacity is improved, but structural stability under high-voltage and high-temperature conditions deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core particles contain high-nickel lithium nickel-manganese-based composite oxide for high capacity, while the surface is coated with aluminium oxide layer and grain boundary coating for stability. This localized differentiation allows the bulk material to maximize capacity while the surface regions provide structural stability and reduce side reactions, achieving both high capacity and long cycle life without requiring cobalt
Solution Approach 2:
The patent uses an aluminium oxide coating layer and grain boundary coating as intermediary substances between the high-nickel core particles and the electrolyte. This intermediary coating acts as a protective barrier that prevents direct interaction between the structurally unstable high-nickel material and the electrolyte under high-voltage and high-temperature conditions. The intermediary layer maintains structural stability by preventing Jahn-Teller distortion and surface degradation, allowing the high-capacity core material to function reliably
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed active material achieves high density, high capacity, and long cycle-life characteristics while minimizing gas production during high-temperature storage, thus addressing the limitations of cobalt-free materials.
Implementation Method 1
an aluminium coating layer on a surface of the core particles, and a grain boundary coating portion that is located on a surface of the primary particles
Data Source
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AI summary
A positive electrode active material for rechargeable lithium batteries includes (a) core particles, including a layered lithium nickel-manganese-based composite oxide, which are in a form of secondary particles, wherein the secondary particles are each an agglomeration of a plurality of primary particles; (b) an aluminium coating layer on a surface of the core particles; and (c) a grain boundary coating portion, which is located on the surface of the primary particles, and which includes cobalt. Also disclosed is a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode.