Battery Separator Copolymer Coating for Heat Shrinkage and Adhesion
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Solution Overview
Problem
Current polyolefin-based separators in lithium secondary batteries suffer from severe heat shrinkage and poor mechanical properties, which can lead to safety issues such as short circuits and explosions, and require improved heat resistance and adhesive strength to maintain battery stability.
Innovation Solution
A copolymer comprising a vinyl acetate-based monomer unit, a vinyl alcohol-based monomer unit, an acrylate-based monomer unit, an acrylic acid-based monomer unit, and an amine-based organic compound is used to create a slurry composition that enhances dispersion stability, adhesive strength, and heat resistance when applied to a separator substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyolefin-based films are used as separators, then ease of manufacture is improved, but heat resistance and mechanical properties deteriorate due to severe heat shrinkage at high temperatures
Solution Approach 1:
The patent uses a composite binder system combining polyacrylic acid and polyvinyl alcohol in specific ratios (0.5:99.5 to 50:50 by weight) to create a coating layer that maintains the polyolefin substrate's manufacturability while adding heat resistance through the composite binder's high-temperature stability and low shrinkage characteristics
2Ease of manufacture
If polyolefin-based films are used as separators, then ease of manufacture is improved, but mechanical properties deteriorate due to poor strength and adhesion
Solution Approach 1:
The patent creates a composite coating layer using polyacrylic acid and polyvinyl alcohol binders with polyolefin particles, where the polyvinyl alcohol component specifically enhances mechanical strength and adhesion to electrodes while maintaining ease of manufacturing through the polyolefin-based substrate
Solution Approach 2:
The patent applies a coating layer with specific binder composition (polyacrylic acid and polyvinyl alcohol) only on the surface of the polyolefin separator substrate, providing enhanced mechanical properties and adhesion where needed (at the electrode interface) while maintaining the bulk substrate's manufacturability
3Reliability
If inorganic particles and binder are coated on porous separator substrate, then heat resistance is improved, but adhesive strength deteriorates due to poor bonding between coating layer and substrate
Solution Approach 1:
The patent uses a composite binder system of polyacrylic acid and polyvinyl alcohol that provides both heat resistance (through high-temperature stability) and strong adhesion to the polyolefin substrate, eliminating the trade-off between these two properties
Solution Approach 2:
The patent optimizes the molecular weight ranges of the binders (polyacrylic acid: 10,000-1,000,000; polyvinyl alcohol: 10,000-500,000) and their weight ratio (0.5:99.5 to 50:50) to achieve both sufficient heat resistance and strong adhesive bonding between the coating layer and substrate
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 copolymer improves the dispersion stability and adhesive strength of the slurry composition, leading to a separator with enhanced heat resistance and improved safety characteristics, effectively addressing the heat shrinkage and mechanical property issues of polyolefin-based separators.
Implementation Method 1
A copolymer of the present disclosure can improve the dispersion stability of a slurry composition
Implementation Method 2
increase adhesive strength to a polyolefin film, which is a separator substrate
Data Source
AI summary
The present invention relates to a copolymer, a slurry composition using same, a separator, and a secondary battery, the copolymer comprising, relative to 100 weight % of the total weight of the copolymer: 3 weight % to 38 weight % of vinyl acetate-based monomer unit; 57 weight % to 81 weight % of vinyl alcohol-based monomer unit; 0.7 weight % to 18 weight % of acrylate-based monomer unit; 14 weight % to 38 weight % of acrylic acid-based monomer unit; and less than 1 weight % of amine organic compound.