Conductive Paste Viscosity Control via Copolymer Resin
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conductive pastes for lithium-ion battery positive electrodes require a low viscosity to facilitate easy application, but existing methods using dispersants in large amounts can negatively impact battery performance, necessitating a dispersant that reduces viscosity with a small amount.
Innovation Solution
A conductive paste comprising a dispersion resin with a specific structure, including a polymerizable unsaturated group-containing monomer, fatty acid vinyl ester, and polyvinyl alcohol, which is copolymerized and saponified to achieve a high saponification degree, combined with a polycyclic aromatic hydrocarbon group-containing resin, to reduce viscosity effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a large amount of dispersant is added to reduce the viscosity of conductive paste, then the viscosity is reduced and application is facilitated, but the battery performance (internal resistance and capacity) is negatively affected
Solution Approach 1:
The invention changes the chemical structure parameters of the dispersant by introducing a specific copolymer composition containing vinyl alcohol units (from saponified fatty acid vinyl ester) and polymerizable unsaturated group-containing monomer units. This structural parameter change enables effective dispersibility at low concentrations (0.1-10 mass%) without the need for large amounts of conventional dispersants, thus reducing viscosity while maintaining battery performance.
Solution Approach 2:
The invention uses a composite dispersant system formed by copolymerizing two different monomer types: (1) fatty acid vinyl ester units that provide dispersibility through hydrolyzed ester groups, and (2) polymerizable unsaturated group-containing monomer units that enable crosslinking and network formation. This composite structure synergistically achieves both low viscosity and maintained battery performance.
2Reliability
If a small amount of dispersant is used to maintain battery performance, then the battery performance is maintained, but the viscosity reduction is insufficient and application becomes difficult
Solution Approach 1:
The invention optimizes the compositional parameters of the copolymer by controlling the ratio of vinyl alcohol units to polymerizable unsaturated group-containing monomer units within 90/10 to 50/50 based on monomer units. This parameter optimization ensures that even at low dispersant concentrations (0.1-10 mass%), the paste achieves sufficiently low viscosity for easy application while maintaining excellent battery performance.
Solution Approach 2:
The copolymer acts as an intermediary substance that mediates between the conductive auxiliary agent particles and the binder/solvent system. The vinyl alcohol units provide strong adsorption to conductive carbon particles, while the polymerizable unsaturated groups enable crosslinking with the binder matrix, creating an optimized intermediate layer that facilitates application at low dispersant concentrations.
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 proposed conductive paste achieves sufficient viscosity reduction with a small amount of dispersion resin, enhancing the dispersibility and solubility of the paste, thereby improving battery performance without compromising internal resistance or capacity.
Implementation Method 1
the resin (A1) is obtained by copolymerization of the monomer (A1-1) and a fatty acid vinyl ester (A1-2)
Implementation Method 2
the copolymerized resin is subjected to saponification so that fatty acid vinyl ester units are hydrolyzed to vinyl alcohol units
Implementation Method 3
the moisture content in the conductive paste is measured by Karl Fischer coulometric titration
Data Source
AI summary
This invention relates to a conductive paste for lithium-ion battery positive electrodes and a mixture paste for a lithium ion battery positive electrode that have an easy-to-apply viscosity, even when a relatively small amount of a dispersion resin is incorporated. More specifically, the invention provides a conductive paste for lithium-ion battery positive electrodes, the conductive paste comprising a dispersion resin (A), conductive carbon (B), and a solvent (C), the dispersion resin (A) containing a resin (A1), the resin (A1) containing, as one constituent component, a polymerizable unsaturated group-containing monomer (A1-1) represented by a specific formula.