Porous Amide-Coated Battery Separator for Thermal Shrinkage Resistance
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Solution Overview
Problem
Existing battery separators face challenges with high shrinkage and low heat stability, particularly at high temperatures, which can lead to electrode exposure, short-circuiting, thermal runaway, and explosions, especially when thinner separators are used to increase capacity.
Innovation Solution
A coated battery separator with a porous polymeric coating comprising a polymer with a high thermal decomposition temperature, such as poly(N-vinylacetamide), which includes a cyclic or non-cyclic amide functional group, is applied to the separator to reduce shrinkage and enhance heat stability, using methods like gas-generating compounds or ceramic removal to create pores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a thin battery separator is used to increase capacity, then capacity is increased, but heat stability and shrinkage resistance deteriorate
Solution Approach 1:
The patent applies composite materials by combining a thin polyolefin separator base layer with a porous coating layer containing high-temperature stable polymers (such as polyacrylonitrile, polyacrylic acid, or carboxymethyl cellulose) and ceramic particles. This composite structure allows the separator to maintain thinness for high capacity while the coating provides thermal stability and shrinkage resistance, resolving the contradiction between thinness and heat stability.
Solution Approach 2:
The patent uses porous materials in the coating layer that contains porous polymers and ceramic particles with porous structures. The porous structure allows ion transport while the high surface area and thermal stability of the porous materials provide heat resistance and prevent shrinkage at elevated temperatures, enabling thin separator design without sacrificing thermal safety.
2Reliability
If a thick coating is provided to prevent shrinkage, then heat stability is improved, but separator thickness increases
Solution Approach 1:
The porous structure of the coating layer provides high thermal stability and shrinkage resistance with lower material density. The porous polymers and ceramic particles create a three-dimensional network that maintains structural integrity at high temperatures without requiring a thick coating, thus preventing shrinkage while keeping the separator thin.
Solution Approach 2:
The coating is applied locally on the separator surface rather than requiring uniform thick coverage throughout. The porous coating layer with concentrated ceramic particles provides localized thermal management and shrinkage prevention at the critical separator surfaces, achieving heat stability with minimal thickness addition.
3Reliability
If a porous coating is applied to reduce shrinkage, then heat stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent controls the porous structure parameters of the coating layer, including pore size, porosity, and particle distribution, to optimize both thermal performance and manufacturability. By adjusting parameters such as ceramic particle size (0.1-10 micrometers) and polymer-to-ceramic ratios, the coating achieves high thermal stability while maintaining compatibility with existing battery manufacturing processes.
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 coated separator achieves low shrinkage of less than 1% at 120°C and less than 5% at 150°C, providing improved safety and stability against thermal runaway and explosions.
Implementation Method 1
The polymer in the porous polymeric coating has a high thermal decomposition temperature. For example, the decomposition temperature may be greater than 200° C., 250° C., 300° C., 350° C., or 400° C.
Implementation Method 2
At high temperatures, ceramic-coated separators may shrink unless a thick coating is provided. The coated battery separator exhibits an MD shrinkage less than 1% at 120° C. MD shrinkage at 150° C. may be less than 5%.
Implementation Method 3
A coated battery separator comprising a battery separator with a porous polymeric coating
Data Source
AI summary
A coated battery separator, comprising the battery separator; and a porous coating on at least one side of the battery separator, wherein the porous coating comprises a polymer comprising an amide functional group.