Cathode Active Material Surface Fluorination Without Washing Damage
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Solution Overview
Problem
The degradation of electrochemical properties and stability of lithium composite oxide-based positive electrode active materials in lithium secondary batteries is caused by lithium impurities such as LiOH and Li2CO3 on the surface, which is exacerbated by conventional washing processes that damage the surface and lead to premature degradation.
Innovation Solution
A fluorine-containing coating layer is formed on the surface of the lithium composite oxide by reacting lithium impurities with a fluorine-containing raw material, effectively reducing the content of lithium impurities without a washing process, thereby maintaining the electrochemical properties and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a washing process is performed to remove lithium impurities from the surface of lithium composite oxide, then the content of lithium impurities is reduced, but the surface of the lithium composite oxide is damaged leading to degradation of electrochemical properties and stability
Solution Approach 1:
The patent converts the harmful lithium impurities (LiOH, Li2CO3) on the surface into beneficial LiF coating by reacting them with fluorine-containing compounds during the heat treatment process. This transforms the harmful substances that would otherwise require washing into a protective coating layer that improves battery performance and stability.
Solution Approach 2:
The patent performs preliminary removal of lithium impurities during the heat treatment process itself, before the material is used in battery assembly. By adding fluorine-containing compounds during heat treatment, the impurities are converted to LiF in advance, eliminating the need for subsequent washing processes that would damage the surface.
2Quantity of substance
If the content of nickel in lithium composite oxide is increased to improve reversible capacity, then high discharge capacity is achieved, but cation mixing increases reducing stability and increasing lithium impurities on the surface
Solution Approach 1:
The patent changes the chemical composition parameters by introducing fluorine-containing compounds during heat treatment. This modifies the surface chemistry to form LiF coating, which stabilizes the high-nickel lithium composite oxide structure and suppresses cation mixing, thereby maintaining both high capacity and stability.
Solution Approach 2:
The patent creates a composite structure where the high-nickel lithium composite oxide core is coated with a fluorine-containing protective layer (LiF). This composite material approach allows the inner high-nickel material to provide high reversible capacity while the outer fluorine-containing layer provides stability and prevents further degradation.
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 method prevents and mitigates the degradation of electrochemical properties and stability by controlling the content of lithium impurities, ensuring improved performance and longevity of the positive electrode active material.
Implementation Method 1
A fluorine-containing coating layer is formed on the surface of the lithium composite oxide by reacting lithium impurities with a fluorine-containing raw material
Data Source
AI summary
The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more particularly, to a positive electrode active material capable of preventing and/or mitigating the degradation of electrochemical properties and lifetime of the positive electrode active material caused by lithium impurities and/or a washing process by removing lithium impurities through surface modification without a washing process for reducing the content of lithium impurities such as LiOH and Li2CO3 remaining on the surface of the positive electrode active material, and a lithium secondary battery using a positive electrode including the positive electrode active material.