Coated Cathode Active Material for High-Temperature Battery Stability
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Solution Overview
Problem
Current cathode active materials in lithium ion secondary batteries face challenges such as capacitance deterioration, increased internal resistance, and insufficient cycle characteristics, especially under high temperature conditions, due to issues with lithium ion diffusion and electron conductivity.
Innovation Solution
A cathode active material is developed with a composite oxide particle containing lithium and transition metals, coated with a layer of elements from Groups 2 to 16 and a halogen, where the coating elements exhibit different distribution states, including lithium fluoride, to enhance charge/discharge performance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the charge voltage is raised to increase energy density, then the battery capacitance increases, but capacitance deterioration occurs and battery life is shortened
Solution Approach 1:
A coating layer containing element M and halogen element X is introduced as an intermediary between the cathode active material and the electrolyte. This coating layer mediates the interaction at the interface, reducing harmful reactions while allowing beneficial charge/discharge processes to occur, thus enabling high voltage operation without severe capacitance deterioration
Solution Approach 2:
The coating layer changes the chemical and physical parameters at the electrode-electrolyte interface. By controlling the composition (element M from Groups 2-16 and halogen element X) and distribution states, the coating modifies the interface properties to suppress degradation reactions that occur at high charge voltages, thereby extending battery life
2Temperature
If the battery is used under high temperature environment, then the operating conditions are expanded, but internal resistance increases and sufficient battery capacitance cannot be extracted
Solution Approach 1:
The coating layer acts as a thermal intermediary that protects the cathode active material from direct exposure to harsh high-temperature conditions. It stabilizes the interface during thermal stress, preventing the formation of high-resistance layers and maintaining low internal resistance even at elevated temperatures
Solution Approach 2:
The coating layer serves as a sacrificial protective layer that can undergo controlled changes at high temperatures to prevent more severe degradation of the underlying cathode active material. This disposable-like coating absorbs thermal damage, maintaining the structural integrity and electrical properties of the bulk material
3Reliability
If a coating layer is applied to improve cycle characteristics, then the cycle life improves, but lithium ion diffusion may be obstructed
Solution Approach 1:
The coating layer exhibits local quality variations through different distribution states of element M and halogen element X. This spatial variation in composition creates regions with different properties: some areas provide enhanced protection for cycle stability, while other areas maintain higher lithium ion conductivity, thus balancing both requirements
Solution Approach 2:
The coating layer is a composite material combining element M (from Groups 2-16) and halogen element X. This composite structure synergistically combines the benefits of both elements: element M provides structural stability and protection, while halogen element X contributes to lithium ion conductivity, achieving both improved cycle characteristics and maintained diffusion rates
Data Source
AI summary
A cathode active material has: a composite oxide particle containing at least lithium and one or a plurality of transition metals; and a coating layer provided on at least a part of the composite oxide particle. The coating layer contains at least one kind of element M differing from a main transition metal element A forming the composite oxide particle and selected from Groups 2 to 16 of the periodic table and a halogen element X. In the coating layer, the element M and the halogen element X exhibit different distribution states.