Lithium Phosphate Coating for High Voltage Battery Stability
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Solution Overview
Problem
Existing lithium ion batteries face limitations in durability and internal resistance, particularly when operating at high voltages, due to oxidative decomposition of the electrolyte solution near the positive electrode.
Innovation Solution
A method for producing a positive electrode active material layer using a slurry containing lithium phosphate as a first lithium salt and a second lithium salt such as lithium hydroxide, which forms a thin coating film on the positive electrode active material particles, inhibiting oxidative decomposition and improving battery durability and internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the maximum operating potential of the positive electrode is raised to increase open-circuit voltage and battery capacity, then battery capacity increases, but oxidative decomposition of the electrolyte solution near the positive electrode during charging is exacerbated
Solution Approach 1:
Lithium phosphate serves as an intermediary substance that forms a protective coating film between the positive electrode active material and the electrolyte solution. This coating film acts as a mediator that prevents direct contact and harmful oxidative decomposition reactions, allowing the electrode to operate at high potentials without suffering from electrolyte decomposition. The lithium phosphate coating enables the system to achieve both high capacity and high stability simultaneously.
Solution Approach 2:
A thin coating film of lithium phosphate is formed on the surface of the positive electrode active material particles. This thin film provides protective functionality while maintaining the electrochemical performance of the electrode. The coating film is sufficiently thin to allow lithium ion transport but sufficiently continuous to prevent electrolyte decomposition, resolving the contradiction between capacity and stability.
2Reliability
If lithium phosphate is used to improve battery durability at high voltage, then durability improves, but internal resistance remains a limiting factor for overall battery performance
Solution Approach 1:
The invention changes the chemical composition parameters of the positive electrode mixture by incorporating lithium phosphate at specific concentrations (0.1-10 wt%). This parameter change modifies the surface properties of the electrode particles, forming a coating that simultaneously improves durability and optimizes ionic conductivity. The specific concentration range is critical to achieving both low internal resistance and high durability without compromising either property.
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 method enhances the durability and internal resistance of lithium ion batteries, especially those operating at high voltages, by forming a protective coating that minimizes electrolyte decomposition, thereby maintaining capacity retention and reducing internal resistance.
Implementation Method 1
coating a substrate with a positive electrode mixture slurry containing a positive electrode active material, a first lithium salt, a second lithium salt and a solvent, and drying off the solvent
Data Source
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AI summary
[PURPOSE] To provide a method for producing a positive electrode active material layer for a lithium ion battery that can improve the durability and internal resistance of a lithium ion battery, and particularly a lithium ion battery that operates at high voltage. [SOLUTION MEANS] The method for producing a positive electrode active material layer for a lithium ion battery according to the invention comprises coating a substrate with a positive electrode mixture slurry containing a positive electrode active material, a first lithium salt, a second lithium salt and a solvent, and drying off the solvent. In the present invention, the first lithium salt is lithium phosphate, the second lithium salt is selected from the group consisting of lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, lithium sulfate and combinations thereof, and the proportion of the second lithium salt with respect to the first lithium salt is 1 to 50 mol% based on the number of lithium atoms.