Positive Electrode Slurry Composition for Anti-Stringing Coating
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Solution Overview
Problem
The formation of string traces at the coating end of positive electrode slurry application in lithium ion secondary batteries leads to deviations in electrode thickness, potentially reducing battery capacity and complicating lead welding, especially when the string trace is long.
Innovation Solution
A method involving the preparation of a positive electrode slurry by dissolving smectite in an aqueous solution with N-methyl-2-pyrrolidone (NMP), followed by thermal dehydration to create a smectite-containing solid mass, which is then mixed with NMP and a positive electrode active material to impart thixotropy, reducing stringing during application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If positive electrode slurry is applied to positive electrode current collector, then electrode coating is formed, but string trace is generated at coating end causing thickness deviation
Solution Approach 1:
The patent changes the chemical composition parameters of the slurry by incorporating smectite clay and specific solvents (NMP, water, ethanol) in controlled ratios. This compositional parameter change modifies the slurry's rheological properties, specifically its thixotropy and surface tension, which directly controls the stringing behavior at the coating end and achieves uniform electrode thickness without string traces.
Solution Approach 2:
The patent uses a composite slurry system combining positive electrode active material (lithium transition metal oxide), smectite clay, and multiple solvents (NMP, water, ethanol). The smectite clay acts as a thickening agent that forms a gel structure, creating a composite material with enhanced anti-stringing properties while maintaining coating quality and electrode performance.
2Ease of operation
If string trace is long at coating end, then electrode thickness deviates, but lead welding becomes difficult
Solution Approach 1:
By adjusting the slurry composition parameters (smectite content, solvent ratios), the patent controls the string trace length to be within an optimal range. This parameter optimization simultaneously achieves uniform electrode thickness and provides sufficient non-coated area on the current collector for lead welding operations.
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 suppresses stringing at the coating end, shortening the string trace length and ensuring consistent electrode thickness, thereby maintaining battery capacity and facilitating lead welding.
Implementation Method 1
subjecting the smectite-NMP aqueous solution to thermal dehydration, to obtain a smectite-containing solid mass
Implementation Method 2
mixing the smectite-containing solid mass, a positive electrode active material, and the N-methyl-2-pyrrolidone (NMP)-containing solvent, to prepare a slurry
Data Source
AI summary
This method for producing a positive electrode slurry comprises: a step wherein an aqueous solution, in which a smectite is dissolved, is mixed with a solvent containing N-methyl-2-pyrrolidone (NMP), thereby preparing an aqueous smectite-NMP solution; a step wherein the aqueous smectite-NMP solution is subjected to thermal dehydration, thereby obtaining a smectite-containing solid content lump; and a step wherein the smectite-containing solid content lump, a positive electrode active material and the solvent containing N-methyl-2-pyrrolidone (NMP) are mixed with each other, thereby preparing a slurry.