Li-Ni-Mn Cathode Composition for High-Voltage Cycle Stability
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Solution Overview
Problem
Existing electrochemical devices face challenges with increased voltage leading to oxygen release, electrolyte decomposition, gas generation, and a sharp decline in cycle performance and high-temperature storage performance.
Innovation Solution
The electrochemical device incorporates a positive active material with specific molar fractions of Li, Ni, and Mn (b/a = 0.4 to 0.6, b/c = 0.8 to 1.2) and an optimized electrolyte solution with fluorinated and ester-based solvents and lithium salt additives to enhance structural stability and improve cycle and high-temperature storage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the voltage of the electrochemical device is increased to increase energy density, then the energy density is improved, but oxygen release from the positive electrode, decomposition of the electrolyte solution, gas generation, and sharp decline in cycle performance occur
Solution Approach 1:
The patent changes the chemical composition parameters of the positive active material by controlling the molar ratios of Li, Ni, and Mn elements. Specifically, it uses a positive active material containing Li, Ni, and Mn with a molar fraction ratio of Ni to Mn (b/c) of 0.8 to 1.2 and Li to Ni (a/b) of 0.85 to 1.15. This parameter optimization enhances structural stability at high voltage while maintaining high capacity, thereby improving both energy density and cycle performance simultaneously.
Solution Approach 2:
The patent employs a composite positive active material comprising multiple elements (Li, Ni, Mn) in specific proportions to create a material with optimized properties. The composite structure combines the high capacity benefits of nickel with the structural stability provided by manganese and lithium, achieving a balance between high energy density and improved cycle performance at elevated voltages.
2Use of energy by moving object
If the voltage of the electrochemical device is increased to increase energy density, then the energy density is improved, but release of oxygen from the positive electrode and decomposition of the electrolyte solution occur
Solution Approach 1:
The patent optimizes the chemical composition parameters of the positive active material by precisely controlling the molar ratios of Li, Ni, and Mn. The specific parameter range of Ni/Mn (b/c) = 0.8 to 1.2 and Li/Ni (a/b) = 0.85 to 1.15 creates a material structure that enhances oxygen release resistance and electrolyte stability at high voltage, thereby reducing harmful side reactions while maintaining high energy density.
Solution Approach 2:
The patent converts the potential harm of high-voltage operation into a benefit by designing a positive active material composition that specifically addresses the instability issues. The optimized Li-Ni-Mn composite material transforms the high-voltage condition, which would normally cause oxygen release and electrolyte decomposition, into an operable state that maintains structural integrity and chemical stability.
3Use of energy by moving object
If the voltage of the electrochemical device is increased to increase energy density, then the energy density is improved, but gas generated by the electrode assembly occurs
Solution Approach 1:
The patent controls the molar composition parameters of the positive active material to suppress gas-generating side reactions. By maintaining Ni/Mn (b/c) ratio of 0.8 to 1.2 and Li/Ni (a/b) ratio of 0.85 to 1.15, the material structure becomes more stable at high voltage, reducing electrolyte decomposition and oxygen release that lead to gas generation, thereby improving both energy density and operational stability.
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 solution enhances the structural stability of the positive active material, improving cycle performance and high-temperature storage performance by reducing interface reactions and maintaining lithium salt concentration, thereby maintaining conductivity and reducing internal resistance.
Implementation Method 1
The fluorinated solvents is characterized by high oxidation resistance, and can reduce the interface reaction activity between the positive active material and the electrolyte solution
Implementation Method 2
The lithium salt additives are conducive to maintaining the lithium salt concentration in the electrolyte solution, thereby improving the cycle performance of the electrochemical device
Implementation Method 3
By making the value of b/a range from 0.4 to 0.6 and the value of b/c from 0.8 to 1.2, this application enhances the structural stability of the positive active material
Data Source
AI summary
An electrochemical device includes a positive electrode plate. The positive electrode plate includes a positive active material layer. The positive active material layer includes a positive active material. The positive active material contains three elements Li, Ni, and Mn. A molar fraction of Li in the positive active material is a, a molar fraction of Ni in the positive active material is b, a molar fraction of Mn in the positive active material is c, a value of b/a is 0.4 to 0.6, and a value of b/c is 0.8 to 1.2.