Composite Separator Coating for Thermal Shrinkage and Wettability
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Solution Overview
Problem
Traditional lithium-ion battery separators made from polyolefin materials suffer from severe thermal shrinkage, poor wettability, and inadequate thermal stability, leading to safety concerns such as short circuits and explosions, especially in high-energy-density batteries.
Innovation Solution
A modified composite separator is developed with a coating comprising high-temperature resistant polymer microspheres, nanofibers, and inorganic particles, which provides improved thermal protection, wettability, and electrolyte retention, enhancing the safety and performance of lithium-ion batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional polyolefin separators are used, then good tensile properties and pore size distribution are achieved, but severe thermal shrinkage occurs at high temperature leading to safety issues
Solution Approach 1:
The patent applies composite materials by combining polyolefin base membrane with ceramic coatings (alumina, silica, boehmite) to create a separator that maintains the mechanical strength of polyolefin while adding high-temperature stability from the ceramic layer, preventing thermal shrinkage at elevated temperatures
2Stability of the object's composition
If traditional polyolefin separators are used, then chemical stability is maintained, but poor wettability with electrolyte results due to non-polar nature
Solution Approach 1:
The patent applies local quality by modifying only the surface of the polyolefin separator with ceramic coatings and polar functional groups, maintaining the bulk chemical stability of polyolefin while improving surface wettability with electrolyte through the coated layer's polar characteristics
3Temperature
If ceramic coatings are applied to improve wettability and temperature resistance, then thermal protection is enhanced, but coating peeling and powder loss occur due to poor compatibility
Solution Approach 1:
The patent uses silane coupling agents as intermediaries between the polyolefin base membrane and ceramic coatings, creating chemical bonds that improve interfacial compatibility and prevent coating peeling and powder loss while maintaining thermal protection benefits
Solution Approach 2:
The patent modifies surface parameters of the ceramic coating through controlled coating thickness (0.5-5 μm), particle size distribution (1-10 μm), and compositional ratios to optimize both thermal resistance and adhesion strength, preventing coating failure
4Productivity
If separator porosity is increased to improve lithium ion conductivity, then ion transport is enhanced, but mechanical strength and thermal stability deteriorate
Solution Approach 1:
The patent uses composite materials where the ceramic coating layer provides structural reinforcement to the porous polyolefin matrix, allowing high porosity (30-80%) for ion conductivity while the ceramic network maintains mechanical strength and 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 modified composite separator significantly reduces thermal shrinkage, improves electrolyte absorption, and increases the cycle life and rate capability of lithium-ion batteries, addressing the safety and stability issues of traditional separators.
Implementation Method 1
The coating comprises at least two of high temperature resistant polymer microspheres, high temperature resistant polymer nanofibers and inorganic particles... improves electrolyte absorption
Implementation Method 2
The coating... provides improved thermal protection, wettability, and electrolyte retention
Data Source
AI summary
The present invention relates to the technical field of battery separators and provides a coated modified composite separator, a preparation method thereof and a coating slurry for preparing the composite separator. The coated modified composite separator includes a base membrane and a coating, wherein the coating is coated on either any one side or both sides of the base membrane, and the coating comprises at least two of the following: b2.1 high temperature resistant polymer microspheres, b2.2 high temperature resistant polymer nanofibers, and b2.3 inorganic particles. The coating in the modified composite separator of the present invention notably enhances the thermal dimensional stability of the base membrane, decreases the areal density of the composite separator, boosts the battery's energy density, lowers the probability of occurrence of thermal runaway, and improves battery safety.