Positive Electrode Material Washing With Weak-Acid pH Control
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Solution Overview
Problem
Current methods for washing lithium composite transition metal oxides struggle to effectively adjust the amount of lithium by-products and selectively remove LiOH and Li2CO3, leading to issues with thermal stability and battery performance.
Innovation Solution
A method involving a lithium composite transition metal oxide with a Ni content of 60 mol % or more, washed in water with a weak acid to adjust the pH to 7-10, allowing for the selective removal of LiOH and Li2CO3, thereby controlling the lithium by-product ratio on the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If water washing is used to remove lithium by-products, then LiOH and Li2CO3 can be removed, but it is impossible to selectively remove LiOH and Li2CO3 and control their proportions
Solution Approach 1:
The patent applies parameter changes by adjusting the pH value of the washing solution to selectively remove LiOH and Li2CO3. By controlling the pH within specific ranges (7-9 for LiOH, 4-6 for Li2CO3), the method achieves selective removal and precise control of lithium by-product proportions, resolving the contradiction between manufacturing precision and selective removal capability.
2Reliability
If all lithium by-products are removed, then battery performance improves, but side reactions and corrosion of the NCM-based lithium oxide surface occur
Solution Approach 1:
The patent applies partial action by intentionally retaining a controlled amount of lithium by-products (0.1-5 wt% total lithium content) on the NCM-based lithium oxide surface. This partial retention prevents surface corrosion and side reactions while maintaining acceptable battery performance, resolving the contradiction between reliability and harmful factors.
Solution Approach 2:
The patent uses parameter changes by controlling the pH value during washing to selectively remove specific lithium by-products while retaining others. This allows precise control over the composition and amount of residual lithium compounds, optimizing the balance between battery performance and surface stability.
3Stability of the object's composition
If LiOH and Li2CO3 remain on the surface, then thermal stability improves, but LiOH increases pH causing gelation and Li2CO3 generates gases
Solution Approach 1:
The patent applies parameter changes by controlling the pH value of the washing solution to selectively remove LiOH (which causes gelation) at pH 7-9, while retaining or removing Li2CO3 (which generates gases) at pH 4-6. This selective removal based on pH control resolves the contradiction by eliminating harmful effects while maintaining thermal stability through controlled retention of beneficial lithium compounds.
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 approach effectively adjusts the washing amount of lithium by-products, improving thermal stability and battery performance by inhibiting gas generation and enhancing capacity and lifetime characteristics.
Implementation Method 1
adding a weak acid to the water to which the lithium composite transition metal oxide is input to adjust the pH to 7 to 10
Data Source
AI summary
A method of washing a positive electrode active material includes (1) preparing a lithium composite transition metal oxide which contains Ni, Co and Mn, and has the Ni content of 60 mol % or more; (2) putting the lithium composite transition metal oxide into water; and (3) adding a weak acid to water to which the lithium composite transition metal oxide is added to adjust the pH to 7 to 10, wherein the acid is a weak acid.