LiF Coated Lithium Transition Metal Composite Oxide for Battery Stability
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Solution Overview
Problem
Lithium transition metal composite oxides in lithium secondary batteries experience a decrease in calcination temperature with increasing nickel content, leading to the accumulation of Li-containing impurities on the surface, which decompose and react with the electrolyte to generate gases, thereby reducing the battery's lifespan.
Innovation Solution
A positive active material with a lithium transition metal composite oxide core coated with a LiF layer, formed using fluoride-based compounds, to reduce the amount of Li-containing impurities such as Li2CO3 and LiOH on the surface, thereby preventing gas generation and improving lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content in lithium transition metal composite oxide is increased to achieve high capacity, then the battery capacity is improved, but the calcination temperature decreases leading to increased Li-containing impurities on the surface
Solution Approach 1:
The patent applies preliminary action by performing surface treatment with fluoride-based compounds before the positive active material is used in the battery. This pre-treatment converts Li-containing impurities (Li2CO3, LiOH) on the surface into LiF, preventing their decomposition and gas generation during subsequent battery operation. The surface treatment is conducted in advance during the material preparation stage, allowing the high-nickel material to be manufactured with acceptable purity while ensuring stable battery performance.
2Ease of manufacture
If Li-containing impurities such as Li2CO3 and LiOH remain on the surface of positive active material, then the material can be obtained from standard synthesis, but these impurities decompose during charge to generate gases reducing battery lifespan
Solution Approach 1:
The patent converts the harmful Li-containing impurities into beneficial LiF coating through fluoride treatment. The impurities Li2CO3 and LiOH that would normally decompose and generate CO2 gas are transformed into stable LiF compounds. This conversion changes the nature of the surface layer from harmful (gas-generating) to beneficial (protective coating), allowing the battery to achieve long lifespan while using standard synthesis methods that produce these impurities.
3Object-generated harmful factors
If surface treatment is performed to remove Li-containing impurities, then gas generation is decreased, but additional processing steps are required
Solution Approach 1:
The patent applies parameter changes by modifying the chemical state of the surface through fluoride-based treatment. Instead of physically removing impurities through multiple mechanical or separation steps, the method changes the chemical parameter of the surface layer by converting Li2CO3 and LiOH into LiF. This single chemical transformation step effectively eliminates gas generation while adding minimal processing complexity, as the fluoride treatment can be performed in a straightforward solution-based process.
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 LiF coating layer effectively decreases gas generation and maintains high capacity, enhancing the chemical stability and lifespan of lithium secondary batteries by limiting the amount of Li-containing impurities to 0.25 parts by weight or less on the surface of the lithium transition metal composite oxide core.
Implementation Method 1
The LiF coating layer effectively decreases gas generation and maintains high capacity, enhancing the chemical stability and lifespan of lithium secondary batteries
Implementation Method 2
A positive active material with a lithium transition metal composite oxide core coated with a LiF layer, formed using fluoride-based compounds
Data Source
AI summary
Provided are a positive active material that has a decreased amount of Li-containing impurities that remain on a lithium transition metal composite oxide surface to decrease an amount of gas generation and has improved lifespan properties, a method of preparing the same, a positive electrode for a lithium secondary battery including the positive active material, and a lithium secondary battery including the same.