Layered Lithium Composite Cathode for Capacity and Thermal Stability
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Solution Overview
Problem
Conventional non-aqueous electrolyte secondary batteries face challenges in achieving both increased charge capacity and thermal stability, as Li2NiO2 in the positive electrode has poor reversibility and can decrease battery capacity, and enhancing charge capacity lowers the pyrolysis temperature.
Innovation Solution
A lithium-metal composite oxide with a specific composition and structure, represented by the formula xLiyNizM1-zO2-(1−x)LiwNizM1-zO2, is used as the positive electrode active material, where Ni content is optimized to enhance charge capacity while maintaining thermal stability by coordinating Li at a tetrahedral position of oxygen, and the negative electrode includes materials like Si and Sn to support Li ion reversibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li2NiO2 is included in the positive electrode to supply sufficient Li ions, then charge capacity is improved, but thermal stability deteriorates and reversibility of Li ion intercalation/deintercalation decreases
Solution Approach 1:
The patent changes the chemical composition parameters by using Li1.2Ni0.6Mn0.2O2 instead of conventional Li2NiO2, adjusting the stoichiometric ratios to achieve both high charge capacity and improved thermal stability. This parameter optimization allows the material to supply sufficient Li ions while maintaining structural stability at elevated temperatures.
Solution Approach 2:
The patent employs a composite cathode material comprising Li1.2Ni0.6Mn0.2O2 combined with other lithium transition metal oxides or hydroxides. This composite approach leverages the high capacity of the nickel-rich phase while the manganese component provides thermal stability, thus resolving the contradiction between charge capacity and thermal stability.
2Quantity of substance
If charge capacity is increased, then battery capacity is improved, but pyrolysis temperature decreases
Solution Approach 1:
The patent optimizes the chemical composition parameters of the cathode material to achieve a balance between charge capacity and pyrolysis temperature. By adjusting the ratios of Li, Ni, Mn and other elements, the material maintains high charge capacity while exhibiting improved thermal stability and higher pyrolysis temperature compared to conventional Li2NiO2-based materials.
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
This approach improves both charge capacity and thermal stability by increasing the pyrolysis temperature while maintaining sufficient charge capacity, addressing the limitations of Li2NiO2 and common carbon-based materials.
Implementation Method 1
Li2NiO2 has poor reversibility of intercalating and deintercalating Li ions
Implementation Method 2
supply a sufficient amount of Li ions to the negative electrode during charge
Data Source
AI summary
This positive electrode active material contains a lithium metal composite oxide which is represented by general formula xLiyNizM1-zO2-(1−x)LiwNizM1-zO2 (wherein 0.1<x≤1, 1.5≤y≤2.5, 0.4<z≤0.9, 0.9≤w≤1.5, and M represents one or more elements that are selected from the group consisting of transition metals, Al, Si, Sn, Ge, Sb, Bi, Mg, Ca and Sr); and the lithium metal composite oxide has a layered structure, while comprising Li element that is coordinated to the position of the oxygen tetrahedron.