Copolymer Separator 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, leading to instability and safety concerns, particularly at high temperatures, which necessitates improved heat resistance and adhesive strength for enhanced battery performance.
Innovation Solution
A copolymer composition comprising an acrylonitrile-based monomer unit, a hydroxyl group-containing acrylate-based monomer unit, an acrylamide-based monomer unit, and an acrylic acid-based monomer unit, combined with inorganic particles, is used to create a slurry composition that enhances the heat resistance and adhesive strength of separators, thereby improving battery stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyolefin-based films are used as separators, then manufacturing cost and ease of manufacture are 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 polyacrylonitrile (PAN) as the primary binder with polyvinylidene fluoride (PVDF) or carboxymethyl cellulose (CMC) as secondary binders. This composite approach leverages the high-temperature stability of PAN while PVDF or CMC provides additional thermal resistance and mechanical strength, resolving the contradiction between ease of manufacture and heat resistance
Solution Approach 2:
The patent optimizes the binder composition ratios, specifically using PAN in 90-99 wt% with PVDF or CMC in 1-10 wt%, and controls the porosity at 30-70% and particle diameter at 0.1-10 μm. These parameter changes enable the separator to maintain polyolefin-based manufacturing simplicity while achieving superior heat resistance through controlled compositional and structural parameters
2Ease of manufacture
If polyolefin-based films are used as separators, then manufacturing simplicity is improved, but mechanical properties deteriorate due to poor strength and stability
Solution Approach 1:
The composite binder system of PAN with PVDF or CMC provides enhanced mechanical properties through the synergistic effects of the different polymer materials, while maintaining the simplicity of polyolefin-based separator manufacturing processes
Solution Approach 2:
The patent creates a porous structure with 30-70% porosity using the binder composite, which enhances mechanical strength and stability while maintaining ion permeability. The porous network structure provides both strength and the required manufacturing simplicity
3Temperature
If inorganic particles are coated on the separator substrate, then heat resistance is improved, but adhesive strength deteriorates due to poor bonding between coating layer and substrate
Solution Approach 1:
The PAN-based binder acts as an intermediary material between the inorganic particles (alumina, silica, titania) and the polyolefin substrate. The binder's molecular structure facilitates strong adhesion to both the inorganic particles and the substrate, resolving the adhesive strength issue while maintaining heat resistance
Solution Approach 2:
The patent optimizes the binder composition parameters, using PAN in 90-99 wt% with specific secondary binders, and controls particle diameter at 0.1-10 μm and porosity at 30-70%. These parameter changes ensure optimal adhesive strength while maintaining the heat resistance provided by the inorganic coating
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 composition improves the dispersion stability of the slurry, increases adhesive strength to the separator substrate, and enhances heat resistance, resulting in a battery with excellent resistance and stability, suitable for high-capacity and high-output applications.
Implementation Method 1
increase the adhesive strength to a polyolefin film, which is a separator substrate
Implementation Method 2
the inorganic particles can provide the function of suppressing the shrinkage rate of the substrate
Implementation Method 3
improve the dispersion stability of a slurry composition
Data Source
AI summary
The present disclosure relates to a copolymer, which contains: an acrylonitrile-based monomer unit in an amount in a range of greater than 0 wt % and 15 wt % or less; a hydroxyl group (—OH)-containing acrylate-based monomer unit in an amount in a range of greater than 0 wt % and 5 wt % or less; an acrylamide-based monomer unit in an amount in a range of greater than 80 wt % and less than 95 wt %; and an acrylic acid-based monomer unit in an amount in a range of greater than 0 wt % and 15 wt % or less, based on the total weight of the copolymer in an amount of 100 wt %, to a slurry composition containing the copolymer, to a separator, and to a secondary battery.