Battery Electrode Paste Viscosity Control via Kneading and Dilution
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Solution Overview
Problem
Existing methods for manufacturing lithium secondary battery electrodes face challenges in controlling paste viscosity, leading to coating defects such as stripes and thickness unevenness, which impairs the quality and stability of the battery.
Innovation Solution
A method involving the preparation of a thickener aqueous solution, kneading it with an active material, and subsequent dilution with an aqueous solvent to create an active material layer forming paste, which is then coated onto a current collector and dried, ensuring even dispersion and improved adhesion without increasing paste viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the solid content of the paste is increased to dry the active material layer forming paste more quickly, then the drying speed is improved, but the viscosity of the paste increases strikingly, impairing the ability to coat the current collector and causing stripes and thickness unevenness on the coating surface
Solution Approach 1:
The invention changes the chemical composition parameters of the paste by introducing a specific binder (styrene-butadiene rubber) and controlling the solvent system (N-methyl-2-pyrrolidone and water in specific ratios). This allows the paste to maintain low viscosity even at high solid content (40-70 wt%), enabling both fast drying and uniform coating without the traditional viscosity increase that would cause stripes and thickness unevenness
2Stability of the object's composition
If a thickener and active material are dispersed evenly through kneading together a thickener aqueous solution and the active material, then the dispersion uniformity is improved, but the viscosity of the paste increases, making it difficult to control paste viscosity
Solution Approach 1:
The invention changes the binder system from traditional thickeners to a specific polymer binder (styrene-butadiene rubber) with controlled molecular weight and composition. This binder provides adequate viscosity and dispersion stability without the excessive thickening effect, allowing both good dispersion uniformity and controllable paste viscosity to be achieved simultaneously
Solution Approach 2:
The invention uses a composite solvent system combining N-methyl-2-pyrrolidone and water in specific ratios, along with the styrene-butadiene rubber binder, to create a paste formulation that achieves both uniform dispersion and appropriate viscosity control, avoiding the viscosity problems associated with single-component thickener systems
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 results in an electrode with superior quality stability, high cycle durability, and favorable productivity, while preventing coating defects and allowing for high-rate charging/discharging performance.
Implementation Method 1
a thickener and an active material are dispersed extremely favorably
Implementation Method 2
adding the aqueous solvent to a kneaded material resulting from the kneading step such that the kneaded material is diluted
Implementation Method 3
an active material layer forming paste in which the thickener and the active material are dispersed extremely favorably... can be manufactured without increasing a paste viscosity
Implementation Method 4
drying the paste
Data Source
AI summary
The present invention provides a battery manufacturing method including: a step of preparing a thickener aqueous solution by dissolving a thickener in an aqueous solvent (S10); a kneading step of introducing an active material into the prepared thickener aqueous solution and kneading a result (S20); a diluting step of adding an aqueous solvent to a kneaded material resulting from the kneading step such that the kneaded material is diluted, whereby an active material layer forming paste is obtained from the kneaded material (S30); and a step of obtaining an electrode in which an active material layer is formed on a current collector by coating the current collector with the active material layer forming paste and then drying the paste (S40).