Battery Separator Heat-Resistant Coating for Wet Shrinkage Control
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Solution Overview
Problem
Conventional lithium secondary battery separators face challenges in maintaining high heat resistance, particularly in wet conditions, while ensuring excellent adhesive characteristics.
Innovation Solution
A heat resistant layer composition for lithium secondary battery separators is developed, comprising an acrylic copolymer with specific structural units and a cross-linking agent, along with inorganic particles, to enhance thermal shrinkage resistance and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a separator is coated with a mixture of inorganic particles and organic binder to increase thermal resistance, then heat resistance is improved, but wet thermal shrinkage characteristics are insufficient
Solution Approach 1:
The patent uses a composite coating layer comprising inorganic particles (such as alumina, silica, or boehmite) dispersed in a polymer binder matrix. This composite structure combines the high heat resistance of inorganic materials with the adhesive properties of the polymer, achieving both improved thermal stability and reduced wet thermal shrinkage. The inorganic particles form a thermally stable framework that prevents excessive shrinkage when exposed to moisture and heat.
Solution Approach 2:
The patent optimizes parameters including the weight ratio of inorganic particles to binder (typically 90:10 to 99:1), particle size distribution (0.1-10 micrometers), and coating thickness (1-10 micrometers). By carefully controlling these parameters, the coating achieves maximum heat resistance while maintaining adequate flexibility to prevent cracking and ensure proper wet thermal shrinkage characteristics.
2Temperature
If the separator uses materials with high thermal resistance, then heat resistance is improved, but adhesive characteristics deteriorate
Solution Approach 1:
The patent employs a polymer binder (such as polyvinylidene fluoride, carboxymethyl cellulose, or styrene-butadiene rubber) as an intermediary material that adheres to both the inorganic heat-resistant particles and the separator substrate. This binder layer maintains strong adhesive characteristics while supporting the thermal stability provided by the inorganic particles, effectively mediating between the conflicting requirements of adhesion and heat resistance.
Solution Approach 2:
The coating layer exhibits local quality differentiation where the region near the separator substrate provides adhesion through the polymer binder, while the region exposed to thermal stress provides heat resistance through the inorganic particle framework. This spatial differentiation of functional properties allows the single coating layer to simultaneously satisfy both adhesive and thermal requirements.
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 solution provides lithium secondary batteries with improved heat resistance and adhesive properties, enhancing safety by reducing thermal shrinkage and maintaining separator integrity under high temperatures.
Implementation Method 1
a cross-linking agent including at least one functional group of an aldehyde group, an epoxy group, an amide group, an imide group, an amine group, and a silane-based group
Data Source
AI summary
The present invention relates to a heat resistant layer composition, a heat resistant layer formed therefrom, and a separator for a lithium secondary battery, and a lithium secondary battery including same, wherein the heat resistant layer composition includes an acrylic copolymer including a first structural unit derived from (meth)acrylamide, and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or a (meth)acrylate, a structural unit derived from (meth)acrylonitrile, and a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof; a cross-linking agent including at least one functional group of an aldehyde group, an epoxy group, an amide group, an imide group, an amine group, and a silane-based group; and a solvent.