Polycarboxylic Acid Binder for Battery Porous Membrane Moisture Control
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Solution Overview
Problem
Cellulose-based polymers like carboxymethyl cellulose in secondary battery porous membranes have high hydrophilicity, leading to increased moisture content, which impairs battery performance, and their slurry preservation stability is low, complicating manufacturing.
Innovation Solution
A binder composition for secondary battery porous membranes using a specific polycarboxylic acid with a carboxylic acid group-containing monomer unit and alkyl (meth)acrylate units, which is water-insoluble at acidic pH and soluble at alkaline pH, providing high preservation stability and appropriate viscosity for the slurry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cellulose-based polymer such as carboxymethyl cellulose is used as a binder in the slurry, then the slurry can be prepared with favorable physical properties such as viscosity, but the polymer increases the content of moisture remaining in the porous membrane after drying, which impairs battery performance
Solution Approach 1:
The patent changes the chemical composition parameter by replacing cellulose-based polymers with a specific copolymer containing carboxylic acid groups and hydrophobic groups. This compositional parameter change reduces the hydrophilicity of the binder, thereby reducing the moisture content in the dried porous membrane while maintaining favorable slurry preparation properties.
2Duration of action of stationary object
If a cellulose-based polymer such as carboxymethyl cellulose is used to impart preservation stability to the slurry, then the slurry can be preserved for extended periods, but the preservation stability is actually low and the slurry needs to be prepared immediately before use, complicating manufacturing
Solution Approach 1:
The patent changes the chemical composition parameter by using a copolymer with both carboxylic acid groups and hydrophobic groups. This compositional change provides excellent preservation stability to the slurry, allowing it to be stored for extended periods without deterioration or separation, thereby simplifying the manufacturing process as the slurry no longer needs to be prepared immediately before use.
3Duration of action of stationary object
If a polycarboxylic acid is used as a binder in the slurry, then the preservation stability improves, but the slurry viscosity becomes inappropriate and the application process is affected
Solution Approach 1:
The patent uses a composite polymer structure combining carboxylic acid groups (which provide preservation stability) with hydrophobic groups (which regulate viscosity and improve application properties). This composite material approach allows the binder to simultaneously provide excellent preservation stability while maintaining appropriate slurry viscosity for easy application.
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 binder composition enhances the preservation stability and application ease of the slurry, resulting in improved high-temperature cycle performance and manufacturing efficiency of secondary batteries with reduced moisture content in the porous membranes.
Implementation Method 1
the polymer includes a hydrophobic group in a specific amount... reduces the content of moisture remaining in the porous membrane
Implementation Method 2
a polymer that can be used as a substitute for a part or all of a cellulose-based polymer such as carboxymethyl cellulose... providing favorable physical properties to the slurry
Data Source
AI summary
A binder composition for a porous membrane of a secondary battery, including a polycarboxylic acid and water, wherein the polycarboxylic acid includes a carboxylic acid group-containing monomer unit in an amount of 20% by weight or more and 50% by weight or less, the polycarboxylic acid is water-insoluble at a pH of 6.5 or less and water-soluble at a pH of 8 or more, and the binder composition for a porous membrane of a secondary battery has a pH of 6.5 or less; and a slurry for a porous membrane of a secondary battery using the binder composition, a porous membrane for a secondary battery, and a secondary battery.