Lithium Cobalt Oxide Cathode Shell Coating for High-Voltage Stability
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Solution Overview
Problem
Lithium cobalt oxide-based positive electrode active materials experience structural instability and reduced lifespan when used at high voltages due to side reactions with electrolytes, leading to safety concerns and capacity degradation in secondary batteries.
Innovation Solution
A positive electrode active material particle with a core of lithium cobalt oxide coated with a composite metal oxide shell, comprising metals with oxidation numbers +2 and +3, such as Ti, Mg, or Al, to reduce reactivity with the electrolyte and maintain structural stability, while allowing lithium ion movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high voltage (4.5 V or greater) is applied to lithium cobalt oxide to increase capacity, then battery capacity increases, but structural stability deteriorates and lifespan decreases due to side reactions with electrolyte
Solution Approach 1:
A coating layer comprising a composite oxide of a divalent metal and a trivalent metal is formed on the surface of lithium cobalt oxide particles. This coating layer acts as an intermediary between the lithium cobalt oxide and the electrolyte, preventing direct contact and side reactions while allowing lithium ion diffusion, thereby maintaining structural stability at high voltages
Solution Approach 2:
The coating layer uses a composite oxide structure combining divalent metals (Ti, Mg, Zn, Si, Al, Zr, V, Mn, Nb, Ni) and trivalent metals (Al, Co, Ni, Fe) in specific ratios. This composite material provides both protective function against electrolyte and maintains ion conductivity, resolving the contradiction between protection and performance
2Reliability
If a coating layer composed of single metal (Al, Ti, Mg, or Zr) is applied to lithium cobalt oxide surface, then structural stability improves, but lithium ion movement is interrupted and battery performance deteriorates
Solution Approach 1:
The patent employs a composite oxide coating combining divalent and trivalent metals in a specific ratio (0.125≤t/w≤1 where t is divalent metal content and w is trivalent metal content). This composite structure provides both protective function and ion conductivity pathways, unlike single metal coatings that block ion movement
Solution Approach 2:
The patent optimizes the compositional parameters of the coating layer, specifically the ratio of divalent to trivalent metals and the overall thickness (5-100 nm). By controlling these parameters, the coating maintains structural stability while preserving lithium ion diffusion channels, thus maintaining battery performance
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 composite metal oxide shell enhances the structural stability and lifespan of the positive electrode active material, preventing swelling and capacity degradation at high voltages, thereby improving the performance and safety of secondary batteries.
Implementation Method 1
a shell that is coated on the surface of the core and contains a composite metal oxide
Implementation Method 2
the performances of the secondary batteries deteriorates
Data Source
AI summary
A positive electrode active material particle includes a core that contains lithium cobalt oxide represented by the following Chemical Formula LiaCo(1-x)MxO2-yAy and a shell that is coated on the surface of the core and contains composite metal oxide of a metal with an oxidation number of +2 and a metal with an oxidation number of +3. In particular, M is at least one selected from the group consisting of Ti, Mg, Zn, Si, Al, Zr, V, Mn, Nb and Ni. A is oxygen-substitutional halogen and 1.00≤a≤1.05, 0≤x≤0.05, and 0≤y≤0.001.