Negative Electrode Paste Manufacturing for Lithium Ion Batteries
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Solution Overview
Problem
The existing methods for manufacturing paste for negative electrodes in lithium ion secondary batteries suffer from inferior storage stability, leading to non-uniform active material layers and compromised battery characteristics.
Innovation Solution
A method involving dry-mixing of graphite and conductive auxiliary agents followed by sequential addition and wet-mixing with aqueous solutions containing thickening and binder agents, using specific mixing processes and conditions to enhance dispersibility and stability of the paste components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional paste manufacturing methods are used, then production efficiency is maintained, but storage stability of the paste deteriorates
Solution Approach 1:
The paste manufacturing process is segmented into three distinct stages with different mixing speeds: high-speed mixing (1000-3000 rpm) for initial dispersion, medium-speed mixing (500-1500 rpm) for homogenization, and low-speed mixing (100-500 rpm) for final uniformity. This segmentation allows each stage to optimize for its specific function, improving overall paste stability without sacrificing production efficiency.
Solution Approach 2:
The mixing process employs periodic action by alternating between different mixing speeds in a controlled sequence. The mixer operates at high speed for a predetermined period, then transitions to medium speed, and finally to low speed. This periodic variation in mixing intensity ensures thorough dispersion while preventing excessive energy input that could destabilize the paste formulation.
2Manufacturing precision
If strong shear force mixing is applied, then dispersibility of components is improved, but uniformity of the active material layer deteriorates
Solution Approach 1:
The mixing process dynamically adjusts the shear force by varying the mixing speed through three distinct phases. The high-speed phase provides strong shear force for initial dispersion, while the subsequent medium and low-speed phases gradually reduce shear force to prevent over-mixing and maintain uniformity. This dynamic adjustment resolves the contradiction between dispersibility and uniformity.
Solution Approach 2:
The mixing process maintains continuous useful action by seamlessly transitioning between the three mixing speed phases without interruption. Each phase builds upon the previous one, ensuring that dispersion, homogenization, and uniformity are achieved in a continuous sequence. This continuous multi-stage approach ensures both good dispersibility and uniformity in the final paste.
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 a paste with improved storage stability and uniformity, leading to enhanced battery characteristics and performance in lithium ion secondary batteries.
Implementation Method 1
adding an aqueous solution, which contains the thickening agent, to the mixture, and wet-mixing the resultant mixture
Implementation Method 2
adding an aqueous emulsion solution, which contains the water-based binder, to the paste precursor, and additionally wet-mixing the resultant mixture
Data Source
AI summary
Provided is a method of manufacturing paste for manufacturing of a negative electrode of a lithium ion secondary battery which contains a graphite material, a conductive auxiliary agent, a thickening agent, and a water-based binder. The method includes: a process (A) of dry-mixing the graphite material and the conductive auxiliary agent to prepare a mixture containing the graphite material and the conductive auxiliary agent; a process (B) of adding an aqueous solution, which contains the thickening agent, to the mixture, and wet-mixing the resultant mixture to prepare a paste precursor; and a process (C) of adding an aqueous emulsion solution, which contains the water-based binder, to the paste precursor, and additionally wet-mixing the resultant mixture to prepare the paste for manufacturing of a negative electrode.