Separator Copolymer Coating for Heat-Resistant Battery Adhesion
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Solution Overview
Problem
Conventional polyolefin-based separators for lithium-ion secondary batteries suffer from high thermal shrinkage and poor mechanical properties, necessitating improved adhesive strength and heat resistance to enhance safety and performance.
Innovation Solution
A copolymer comprising specific monomer units, including vinylacetate, acrylate-based, and acrylic acid-based monomers, is used to create a slurry composition that enhances adhesive strength and heat resistance by incorporating alkali metal or acetate salt compounds, which improve cohesion and elasticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based film is used as a separator, then it provides basic insulation and separation function, but it exhibits high thermal shrinkage at high temperature and poor mechanical properties
Solution Approach 1:
The patent applies composite materials by combining polyolefin base material with inorganic particles (such as alumina, silica, or boehmite) and binder polymers to create a separator that maintains the thermal stability of polyolefin while gaining the heat resistance and mechanical strength of inorganic materials. The composite structure allows the separator to resist thermal shrinkage and improve overall mechanical properties.
Solution Approach 2:
The patent changes the physical and chemical parameters of the separator by controlling the particle size distribution (0.1-10 μm), porosity (30-80%), and composition ratios of inorganic particles and binders. These parameter adjustments optimize both thermal stability and mechanical strength, allowing the separator to maintain structural integrity at elevated temperatures while improving tensile and puncture resistance.
2Temperature
If inorganic particles are coated on the separator substrate to suppress thermal shrinkage, then heat resistance improves, but adhesive strength between inorganic particles and substrate may be insufficient
Solution Approach 1:
The patent uses binder polymers (such as polyvinylidene fluoride, polyacrylonitrile, or carboxymethyl cellulose) as intermediary materials between the inorganic particles and the polyolefin substrate. These binders provide adhesive functionality that strongly bonds inorganic particles to the substrate while maintaining porosity and ion permeability. The binder acts as a mediator that ensures strong adhesion without compromising the separator's functional properties.
Solution Approach 2:
The patent applies local quality by creating a multi-layer coating structure where different regions have different functions: the bottom layer provides strong adhesion to the substrate, the intermediate layer ensures particle binding, and the top layer maintains porosity and ion transport. This localized functional differentiation ensures both strong adhesive strength and effective heat resistance throughout the separator structure.
3Reliability
If the coating layer is made thicker to improve safety and shrinkage resistance, then thermal stability improves, but manufacturing complexity and uniformity control become more difficult
Solution Approach 1:
The patent segments the coating layer into multiple thin layers rather than applying one thick coating. Each layer can be independently controlled for uniformity, and the cumulative thickness achieves the desired safety performance. This segmentation simplifies manufacturing by allowing better control of each individual layer's application and drying processes, reducing defects while maintaining or improving thermal stability.
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 increases adhesive strength between inorganic substances and electrodes, improving the mechanical stability and thermal resistance of the separator, thereby reducing battery failure risks and enhancing overall battery performance.
Implementation Method 1
an attempt has been made to develop a porous separator in which a polyolefin porous substrate film is coated with a mixture of inorganic particles and a binder
Implementation Method 2
the inorganic particles impart a function of suppressing shrinkage of the substrate and the coating layer provides the separator with improved safety
Data Source
AI summary
The present invention relates to a copolymer, and a slurry composition, a separator, and a secondary battery that comprise same, wherein the copolymer comprises, based on 100 wt % of the total weight of the copolymer, 15 wt % or less of a vinylacetate monomer unit, 10-55 wt % of an acrylate-based monomer unit, and 1-10 wt % of an acrylic acid-based monomer unit bound with at least one selected from the group consisting of an alkali metal and an acetate salt compound comprising an alkali metal.