Lithium Cobalt Oxide Coating to Suppress High-Voltage Cobalt Elution
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Solution Overview
Problem
Lithium cobalt-based positive electrode active materials experience significant cobalt elution and deterioration of high-temperature storage properties when subjected to high-voltage driving, particularly at voltages of 4.45 V or greater, due to the formation of lithium defect layers during coating with metal oxides.
Innovation Solution
A method involving dry-mixing and heat-treating lithium cobalt oxide particles with lithium metal oxide particles, such as lithium aluminum oxide or lithium titanium oxide, to form a coating layer with an atomic ratio of Li/Co greater than or equal to 1, preventing lithium consumption and defect layer formation, thereby suppressing cobalt elution and enhancing electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal oxide coating is applied to improve structural stability, then electrochemical performance is improved at voltages below 4.45 V, but cobalt elution and gas generation occur rapidly at voltages of 4.45 V or greater
Solution Approach 1:
The patent introduces a lithium-containing coating layer as an intermediary substance between the lithium cobalt oxide particle and the electrolyte. This coating layer, containing lithium compounds such as lithium phosphate, lithium carbonate, or lithium oxalate, mediates the interaction between the active material and electrolyte, preventing direct contact that would cause cobalt elution while maintaining electrochemical performance at high voltages of 4.45 V or greater.
Solution Approach 2:
The patent changes the chemical composition parameters of the coating layer by incorporating lithium-containing compounds with specific lithium-to-metal ratios. By controlling the lithium content and chemical state in the coating layer, the patent achieves suppression of cobalt elution and gas generation while maintaining structural stability and electrochemical performance at high operating voltages.
2Duration of action of moving object
If a lithium defect layer is formed to improve lifespan and output properties, then electrochemical performance is improved, but reactivity with electrolyte increases causing gas generation and cobalt elution
Solution Approach 1:
The patent converts the harmful effect of lithium defect layers into a beneficial solution by intentionally introducing lithium-containing compounds into the coating layer. This approach transforms the lithium deficiency problem into a controlled lithium supplementation strategy, where the coating layer provides the necessary lithium to prevent cobalt elution and gas generation while maintaining improved lifespan properties.
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 approach effectively reduces cobalt elution and maintains excellent electrochemical properties even at high-voltage driving, ensuring superior high-temperature storage stability with a measured cobalt elution amount of 700 ppm or less after two weeks at 60°C.
Implementation Method 1
heat treating a lithium cobalt oxide particle represented by Formula 1 below and a lithium metal oxide particle
Implementation Method 2
dry-mixing and then heat treating a lithium cobalt oxide particle... and a lithium metal oxide particle
Data Source
AI summary
A method for preparing a lithium cobalt-based positive electrode active material and a positive electrode active material prepared by the method are provided. The method includes dry-mixing and then heat treating a lithium cobalt oxide particle represented by Formula 1 and one or more lithium metal oxide particle selected from the group consisting of lithium aluminum oxide, lithium zirconium oxide, and lithium titanium oxide.