Plasma Treatment of Cathode Active Material Surfaces
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Solution Overview
Problem
Lithium impurities such as LiOH and LiCO3 on the surface of cathode active materials in lithium secondary batteries cause gelation and swelling issues during electrode production and battery operation, necessitating a method to minimize their surface content.
Innovation Solution
A surface treatment method using plasma generated from gases like fluorine-containing and phosphorus-containing gases to remove lithium impurities from the cathode active material surface, modifying them into non-reactive forms like LiF, thereby reducing their presence to less than 0.3 wt%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium impurities (LiOH, LiCO3) are present on the cathode active material surface, then the electrode slurry can be prepared, but gelation occurs during slurry preparation and swelling phenomenon occurs when reacted with electrolyte components
Solution Approach 1:
The patent applies preliminary action by performing plasma treatment on the cathode active material surface before electrode slurry preparation. This pre-treatment removes lithium impurities (LiOH, LiCO3) from the surface, preventing subsequent gelation during slurry mixing and swelling during battery operation. The plasma treatment is conducted as a preliminary step to ensure impurity-free surface before further processing.
Solution Approach 2:
The patent utilizes parameter changes by altering the chemical state of lithium impurities through plasma treatment. The plasma process transforms lithium compounds (LiOH, LiCO3) into lithium fluoride (LiF) with different chemical properties that do not cause gelation or swelling. This chemical parameter change converts harmful impurities into benign substances.
2Reliability
If lithium impurities are removed from the cathode active material surface, then gelation and swelling are prevented, but additional plasma treatment process is required
Solution Approach 1:
The patent replaces mechanical removal methods (such as grinding, washing, or scraping) with plasma treatment. Instead of physically removing lithium impurities through mechanical means, the plasma process chemically transforms them into lithium fluoride. This substitution provides a more effective and cleaner removal mechanism without the limitations of mechanical methods.
Solution Approach 2:
The patent employs plasma as a strong reactive environment that accelerates the chemical transformation of lithium impurities. The plasma contains highly reactive species that rapidly convert LiOH and LiCO3 into LiF through enhanced chemical reactions. This accelerated chemical process is more efficient than conventional chemical treatment methods.
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 effectively reduces lithium impurities on the cathode active material surface, suppressing side reactions with the electrolyte and preventing swelling phenomena, thereby enhancing the battery's performance and stability.
Implementation Method 1
generating a plasma from gases comprising at least one of a fluorine-containing gas and a phosphorus-containing gas as a part of a reactive gas
Implementation Method 2
removing lithium impurities present on the particle surface of the cathode active material by contact and reaction with the plasma
Implementation Method 3
The step (c) may further comprise sputtering at least part of the lithium impurities with the accelerated ions of the plasma by reaction with plasma ions
Data Source
AI summary
The present invention provides a method for treating the particle surface of a cathode active material for a lithium secondary battery, the method comprising (a) preparing a cathode active material having a lithium compound; (b) generating a plasma from a gas comprising at least one of a fluorine-containing gas and a phosphorus-containing gas as a part of a reactive gas; and (c) removing lithium impurities present on the particle surface of the cathode active material with the plasma. In accordance with the present invention, the amount of the lithium impurities present on the particle surface of the cathode active material can be reduced to suppress a side reaction of the lithium impurities and an electrolyte.