Positive Electrode Washing and Boron Coating for Residual Lithium
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Solution Overview
Problem
Existing nickel-based positive electrode active materials with high nickel content face issues of residual lithium leading to performance degradation, such as long-term lifetime degradation, resistance increase, and gas generation, due to unreacted lithium and by-products on the surface, which react with the electrolyte solution, and repeated lithium movement causing cracks.
Innovation Solution
A method involving simultaneous washing and filtering of lithium transition metal oxide using a filter device with specific washing solutions, followed by drying and forming a boron-containing coating layer to minimize surface degradation and control residual lithium, resulting in a uniform coating layer on the positive electrode active material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of washing solution is used in the washing process, then residual lithium is effectively controlled, but process limitations occur and battery performance degrades due to surface degradation of the positive electrode active material
Solution Approach 1:
The patent changes the chemical composition parameters of the washing solution by adding specific additives (such as chelating agents like EDTA or NH4F) to the washing solution. This allows effective removal of residual lithium while preventing surface degradation of the positive electrode active material, resolving the contradiction between thorough washing and material protection
Solution Approach 2:
The patent introduces a washing solution additive as an intermediary substance that mediates between the washing solution and the positive electrode active material. This additive selectively binds to residual lithium for removal while forming a protective layer that prevents surface degradation, thus enabling effective lithium control without harming the material surface
2Quantity of substance
If high nickel content is used in the positive electrode active material, then battery capacity is improved, but residual lithium increases leading to performance degradation and stability issues
Solution Approach 1:
The patent extracts and removes residual lithium and by-products from the surface of high-nickel positive electrode active material through a specialized washing process. This extraction of harmful residual substances allows the material to maintain high nickel content for capacity while eliminating the reliability issues caused by residual lithium
Solution Approach 2:
The patent creates a composite surface structure on the positive electrode active material by forming a coating layer containing lithium fluoride (LiF) and/or lithium oxalate (Li2C2O4) through the washing process. This composite surface layer combines the high-capacity benefits of high-nickel material with the stability and protection provided by the protective coating
3Duration of action of moving object
If repeated charge and discharge cycles occur, then battery operation is maintained, but cracks occur in the positive electrode active material due to contraction and expansion, adversely affecting long-term performance
Solution Approach 1:
The patent applies a protective coating layer to the surface of the positive electrode active material before battery operation begins. This pre-formed coating layer acts as a cushioning buffer that absorbs and distributes the mechanical stress from repeated contraction and expansion during charge-discharge cycles, preventing crack formation and maintaining structural integrity throughout the battery's operational life
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 controls residual lithium and minimizes surface degradation, leading to improved electrochemical performance and thermal stability of the battery.
Implementation Method 1
mixing a positive electrode active material precursor and a lithium-containing raw material to produce a positive electrode active material, and then washing the positive electrode active material using a washing solution
Implementation Method 2
first filter the lithium transition metal oxide; simultaneously second washing and second filtering the lithium transition metal oxide
Implementation Method 3
mixing a coating element-containing raw material with the dried lithium transition metal oxide and heat-treating the mixture to form a coating layer
Implementation Method 4
forming a uniform coating layer on the surface of the positive electrode active material
Data Source
AI summary
A method for producing a positive electrode active material which can minimize the surface degradation of a positive electrode active material which occurs in a washing process, effectively control residual lithium, and form a uniform coating layer on the surface of the positive electrode active material, the method including the steps of: preparing a lithium transition metal oxide; mixing the lithium transition metal oxide and a first washing solution to first wash and then first filter the lithium transition metal oxide; simultaneously second washing and second filtering the lithium transition metal oxide using a filter device capable of washing and filtering simultaneously with a second washing solution; and drying the lithium transition metal oxide, then mixing a coating element-containing raw material with the dried lithium transition metal oxide and heat-treating the mixture to form a coating layer. A positive electrode active material produced by the method is also provided.