Conductive Material Dispersion for Low-Viscosity Li-Ion Cathode Slurries
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Solution Overview
Problem
Conductive material dispersions used in lithium ion secondary batteries face issues with high viscosity at high concentrations, leading to poor handleability and storage stability, which affects the quality and productivity of electrode pastes, and increases the solvent load and environmental impact.
Innovation Solution
A conductive material dispersion is developed using a combination of polyvinyl acetal-based resin and cellulose-based resin, with specific ratios and properties, to maintain low viscosity and enhance storage stability, allowing for high-concentration conductive material formulations suitable for lithium ion secondary batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the concentration of conductive material in the dispersion is increased to improve conductivity and reduce internal resistance, then the conductivity improves, but the viscosity increases significantly leading to poor handleability
Solution Approach 1:
A dispersant is introduced as an intermediary substance to mediate between the conductive material particles and the dispersion medium. The dispersant adsorbs onto the conductive material surface, providing steric or electrostatic repulsion that prevents aggregation and reduces interparticle friction, thereby maintaining low viscosity even at high conductive material concentrations
Solution Approach 2:
The chemical composition parameters of the dispersion system are changed by selecting specific dispersants with appropriate molecular structures and concentrations. By adjusting the dispersant-to-conductive material ratio and selecting dispersants with optimal hydrophilic-lipophilic balance, the system achieves both high conductivity and low viscosity through modified interfacial properties
2Reliability
If the concentration of conductive material is increased to improve battery performance, then the conductivity improves, but the storage stability deteriorates and viscosity increases with time
Solution Approach 1:
The dispersant acts as a protective intermediary that forms a stable coating around conductive material particles, preventing direct particle-to-particle contact and aggregation over time. This steric barrier maintains uniform dispersion and prevents viscosity increase during storage, ensuring both high performance and long-term stability
Solution Approach 2:
The dispersant provides beforehand cushioning by pre-establishing a protective layer around conductive material particles before aggregation can occur. This preventive mechanism cushions against the natural tendency of particles to aggregate during storage, maintaining dispersion stability and consistent viscosity over extended periods
3Ease of operation
If a low-concentration conductive material dispersion is used to maintain low viscosity and good handleability, then the handleability improves, but the amount of solvent increases and the load in the drying process increases
Solution Approach 1:
The dispersant enables high solid content by mediating particle interactions, allowing the formulation to achieve both low viscosity and high conductive material concentration. This eliminates the need for excess solvent, reducing both material usage and drying load while maintaining excellent handleability
Solution Approach 2:
The dispersion is formulated with optimized parameters including dispersant concentration, conductive material particle size distribution, and dispersion medium selection. These parameter changes enable the system to achieve maximum solid content (70-90 wt%) while maintaining low viscosity and good handleability, thereby minimizing solvent usage and drying energy requirements
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 reduces the kneading time and in-plane variation of positive electrodes, ensures stable battery quality, shortens drying times, decreases solvent usage, and minimizes environmental impact by maintaining low viscosity and stability over time.
Implementation Method 1
a conductive material dispersion containing at least a conductive material, a dispersion medium, a polyvinyl acetal-based resin and a cellulose-based resin
Data Source
AI summary
An object of the present application is to provide a conductive material dispersion having excellent performance, and methods for manufacturing a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery, using the conductive material dispersion. As a means for achieving the object, the conductive material dispersion contains at least a conductive material, a dispersion medium, a polyvinyl acetal-based resin, and a cellulose-based resin, wherein 10-200 parts by weight of the polyvinyl acetal-based resin is contained with respect to 100 parts by weight of the cellulose-based resin.