Electrode Paste Composition for Stable Conductive Slurry Dispersion
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Solution Overview
Problem
Conventional slurries for electrochemical device electrodes face challenges in improving dispersibility and sedimentation resistance, leading to increased internal resistance over time.
Innovation Solution
A paste comprising a conductive material with a fibrous structure, a polymer with specific chemical composition and Mooney viscosity, and a dispersion medium, used in specific proportions to enhance dispersibility and sedimentation resistance, thereby reducing internal resistance in electrochemical devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional slurries are used for electrode mixed material layer formation, then the manufacturing process is simple, but dispersibility is poor and sedimentation occurs readily
Solution Approach 1:
The patent uses a composite binder system comprising both a polyacrylonitrile-based polymer and a carboxymethyl cellulose-based polymer. This composite material approach combines the advantages of both polymers: polyacrylonitrile provides good adhesion and conductivity, while carboxymethyl cellulose enhances dispersibility and sedimentation resistance. The synergistic effect of these two polymers resolves the contradiction by improving slurry stability without requiring complex additives or processing steps.
Solution Approach 2:
The patent optimizes specific parameters of the binder polymers, including the ratio of polyacrylonitrile to carboxymethyl cellulose (1:4 to 4:1 by mass), the degree of substitution of carboxymethyl cellulose (0.6-1.2 mmol/g), and the average molecular weight (10,000-1,000,000). By carefully controlling these parameters, the slurry achieves improved dispersibility and sedimentation resistance while maintaining a relatively simple composition and manufacturing process.
2Reliability
If conductive material is added to improve conductivity, then internal resistance decreases, but sedimentation occurs readily
Solution Approach 1:
The carboxymethyl cellulose-based polymer acts as an intermediary substance between the conductive material particles and the solvent. It adsorbs onto the surface of conductive material particles, providing steric stabilization and preventing aggregation and sedimentation. This intermediary role allows the conductive material to remain uniformly dispersed in the slurry, maintaining both low internal resistance and high sedimentation resistance.
Solution Approach 2:
The composite binder system creates a protective matrix around conductive material particles, preventing their direct contact and subsequent sedimentation. The carboxymethyl cellulose component specifically interacts with conductive material surfaces, forming a stable dispersion that maintains electrical conductivity while preventing settlement during storage and processing.
3Stability of the object's composition
If polymer amount is increased to improve binding, then sedimentation resistance improves, but slurry viscosity increases excessively
Solution Approach 1:
The patent optimizes the total binder content and the specific ratio between polyacrylonitrile and carboxymethyl cellulose to achieve the desired balance. By controlling the degree of substitution of carboxymethyl cellul (0.6-1.2 mmol/g) and the average molecular weight (10,000-1,000,000), the slurry maintains appropriate viscosity while achieving good sedimentation resistance. The synergistic interaction between the two polymers allows for reduced total binder content compared to using a single polymer.
Solution Approach 2:
The two polymers perform different local functions: polyacrylonitrile primarily provides adhesion and conductivity at the electrode-active material interface, while carboxymethyl cellulose primarily provides dispersibility and sedimentation resistance in the bulk slurry. This division of functional responsibilities allows each polymer to work efficiently at its optimal concentration, avoiding excessive viscosity increase while achieving comprehensive performance improvement.
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 solution effectively improves the dispersibility and sedimentation resistance of the slurry, resulting in reduced internal resistance of electrochemical devices over a long period.
Implementation Method 1
the polymer includes a nitrile group-containing monomer unit and an alkylene structural unit and has a Mooney viscosity (ML1+4, 100° C.) of not less than 70 and not more than 150
Data Source
AI summary
A paste for an electrochemical device contains a conductive material, a polymer A, and a dispersion medium. The conductive material includes a fibrous conductive material and is contained in the paste in a proportion of more than 2 mass %. The polymer A includes a nitrile group-containing monomer unit and an alkylene structural unit and has a Mooney viscosity (ML1+4, 100° C.) of not less than 70 and not more than 150. The paste contains the polymer A in a proportion of more than 50 parts by mass and not more than 200 parts by mass per 100 parts by mass of the conductive material.