SWCNT Dispersion Liquid Using CMC for Stable High-Concentration Coating
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Solution Overview
Problem
Single-walled carbon nanotubes have difficulty being stably dispersed in water at high concentrations, limiting their use in electrode coating materials for nonaqueous electrolyte secondary batteries, and existing dispersion liquids achieve only concentrations of 0.4% by mass or less with poor dispersion stability.
Innovation Solution
A carbon nanotube dispersion liquid comprising single-walled carbon nanotubes, carboxymethyl cellulose, and water, with specific molecular weight and etherification ranges for the cellulose, allows for concentrations of 0.47% to 1.00% by mass and improved dispersion stability, incorporating a silicon-based active material for enhanced battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If single-walled carbon nanotubes are dispersed in water at high concentrations, then the concentration of the dispersion liquid is improved, but the dispersion stability deteriorates
Solution Approach 1:
The patent uses carboxymethyl cellulose as an intermediary substance to mediate between single-walled carbon nanotubes and water. The dispersant adsorbs onto the carbon nanotube surface through hydrophobic interactions and steric stabilization, preventing aggregation while enabling high-concentration stable dispersion in aqueous medium
Solution Approach 2:
The patent optimizes specific parameters of carboxymethyl cellulose including degree of substitution (0.3-0.7) and molecular weight (10,000-1,000,000), as well as the ratio of dispersant to carbon nanotubes (5-50 parts by mass), to achieve the optimal balance between high concentration and stable dispersion
2Stability of the object's composition
If conventional dispersants are used to disperse carbon nanotubes, then dispersibility is improved, but the concentration is limited to 0.4% by mass or less
Solution Approach 1:
The patent systematically optimizes the molecular weight and degree of substitution of carboxymethyl cellulose, finding that moderate molecular weight (10,000-1,000,000) and degree of substitution (0.3-0.7) provide the best balance between dispersibility and concentration capability, breaking through the 0.4% concentration limit while maintaining stable dispersion
3Reliability
If single-walled carbon nanotubes are used as conductive agent, then electrical conductivity is improved, but aggregation due to van der Waals forces worsens
Solution Approach 1:
Carboxymethyl cellulose acts as a mediator that adsorbs onto single-walled carbon nanotube surfaces through hydrophobic interactions and steric stabilization, creating a protective layer that prevents van der Waals aggregation while maintaining the electrical conductivity network of carbon nanotubes in the electrode
Solution Approach 2:
The patent creates a composite system combining single-walled carbon nanotubes with carboxymethyl cellulose dispersant, where the dispersant forms a protective interface layer around the carbon nanotubes, preventing aggregation while preserving electrical conductivity properties
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 achieves high-concentration, stable dispersion of single-walled carbon nanotubes, improving electrode coating materials for nonaqueous electrolyte secondary batteries, enhancing battery performance through increased flexibility and cycle characteristics.
Implementation Method 1
carbon nanotubes strongly aggregate due to van der Waals forces, resulting in difficulty in being uniformly dispersed in water
Implementation Method 2
carboxymethyl cellulose and/or a salt thereof having a degree of etherification of 0.65 to 0.85 and a weight-average molecular weight of 120,000 to 250,000
Implementation Method 3
carboxymethyl cellulose and/or a salt thereof having a degree of etherification of 0.65 to 0.85
Data Source
AI summary
Provided is a carbon nanotube dispersion liquid that exhibits good dispersion stability of single-walled carbon nanotubes.A carbon nanotube dispersion liquid according to an embodiment includes single-walled carbon nanotubes, carboxymethyl cellulose and/or a salt thereof, and water, in which a content of the single-walled carbon nanotubes is 0.47% to 1.00% by mass. The carboxymethyl cellulose and/or the salt thereof includes at least one having a degree of etherification of 0.65 to 0.85 and a weight-average molecular weight of 120,000 to 250,000. A content of the carboxymethyl cellulose and/or the salt thereof is 120 to 220 parts by mass relative to 100 parts by mass of the single-walled carbon nanotubes.