High-Nickel Li-Ion Cathode Electrolyte for High-Voltage Stability
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Solution Overview
Problem
High-nickel-containing positive electrode active materials in lithium-ion batteries face challenges with severe phase transition oxygen release, leading to poor high-temperature storage and cycling performance, as well as safety concerns due to oxidative decomposition and dehydrogenation reactions under high voltage.
Innovation Solution
The use of a nickel-containing positive electrode active material with controlled nickel content and fluoroethylene carbonate in the electrolyte, along with additional sulfur-oxygen double-bond compounds and lithium difluorophosphate, forms a stable solid electrolyte interface film, enhancing the battery's high-temperature storage, cycling, and safety performance by limiting nickel content and optimizing electrolyte composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the amount of nickel in nickel-containing positive electrode materials is continuously increased to further increase energy density, then mass-energy density is improved, but severe phase transition oxygen release occurs leading to poor high-temperature storage and cycling performance and safety performance
Solution Approach 1:
The patent optimizes the nickel content parameter in the positive electrode material to a specific range (0.8≤x≤1.0 in LiNixM1-y-zMg1-yMn1-zO2) rather than continuously increasing it, and adjusts the charge cut-off voltage parameter to 4.3V-4.45V to balance energy density with structural stability and prevent oxygen release
Solution Approach 2:
The patent uses composite materials by combining nickel with magnesium and manganese in a specific ratio (LiNixMg1-yMn1-zO2 where y and z are both between 0.05-0.20), creating a multi-element composite that maintains high energy density while improving thermal stability and preventing phase transition
2Use of energy by moving object
If the amount of nickel in nickel-containing positive electrode materials is continuously increased to further increase energy density, then mass-energy density is improved, but severe phase transition oxygen release occurs leading to poor safety performance
Solution Approach 1:
The patent sets the charge cut-off voltage parameter between 4.3V and 4.45V, which is lower than conventional high-voltage charging, to avoid the voltage range where severe oxygen release and oxidative decomposition occur, thereby improving safety while maintaining acceptable energy density
Solution Approach 2:
The magnesium-containing composite structure (LiNixMg1-yMn1-zO2) provides enhanced thermal stability and suppresses oxygen release at high temperatures, improving safety performance while maintaining high nickel content for energy density
3Productivity
If nickel-containing positive electrode materials are used to achieve high energy density, then battery capacity is improved, but oxidative decomposition and dehydrogenation reactions occur under high voltage leading to poor cycling performance
Solution Approach 1:
The patent optimizes the charge cut-off voltage parameter to 4.3V-4.45V and controls the nickel content parameter (x≥0.8) to balance capacity with cycling stability, avoiding the most severe oxidative decomposition zone while maintaining high capacity
Solution Approach 2:
The multi-element composite (LiNixMg1-yMn1-zO2 with controlled y and z values) provides structural reinforcement that resists degradation from oxidative decomposition and dehydrogenation reactions, improving cycling performance while maintaining high capacity
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 configuration significantly improves the battery's impedance, cycle capacity retention, and high-temperature storage swelling rate, ensuring stable operation and safety under high voltage conditions by forming a self-repairing solid electrolyte interface film and reducing oxidative reactions.
Implementation Method 1
forms a stable solid electrolyte interface film
Implementation Method 2
forming a self-repairing solid electrolyte interface film
Implementation Method 3
reducing oxidative reactions
Implementation Method 4
severe phase transition oxygen release
Data Source
AI summary
An electrochemical apparatus including: a positive electrode, where the positive electrode includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material, wherein the positive electrode active material includes lithium nickel oxide and an electrolyte. The electrolyte includes fluoroethylene carbonate, where based on a total mass of the electrolyte, a mass percentage of the fluoroethylene carbonate is a %. In this application, a charge cut-off voltage U V of the electrochemical apparatus, a molar ratio x of nickel in the lithium nickel oxide, and the mass percentage a % of the fluoroethylene carbonate in the electrolyte satisfy the following relationship:a≤2.3x0.7-6x0.1(U-4.2).