Hydrophilic Battery Separator Coating for Electrolyte Wettability
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Solution Overview
Problem
Lithium secondary batteries face challenges with poor heat resistance and mechanical strength in polyolefin-based separators, and existing methods for improving electrolyte impregnability are inefficient, leading to reduced battery performance and productivity.
Innovation Solution
A separator with a porous support coated with a hydrophilic polymer, where the polymer content and solvent are optimized to balance electrolyte impregnability and air permeability, enhancing the hydrophilicity and mechanical properties of the separator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat-resistant layer including ceramic particles is formed on the surface of the separator, then heat resistance is improved, but air permeability is reduced due to pore closure
Solution Approach 1:
The patent uses a porous coating layer containing porous ceramic particles instead of dense ceramic particles. This maintains the pore structure necessary for air and ion permeability while providing heat resistance. The porous structure allows electrolyte and ion transport pathways to remain open while the ceramic material provides thermal stability and shutdown functionality.
Solution Approach 2:
The patent creates a composite coating layer combining organic binder polymers with inorganic ceramic particles (such as Al2O3, SiO2, TiO2, or porous ceramic particles). This composite structure integrates the heat resistance and pore-forming capability of ceramics with the binding and flexibility of polymers, achieving both thermal stability and maintained permeability.
2Reliability
If the separator surface is coated to improve heat resistance, then thermal stability is enhanced, but ion migration path is reduced
Solution Approach 1:
The coating layer is designed with high porosity (50-80%) to ensure that ion migration pathways remain open and unobstructed. The porous ceramic particles and binder polymer structure create a three-dimensional network that allows efficient ion transport while providing thermal stability through the ceramic component.
Solution Approach 2:
The coating layer provides localized heat resistance only at the separator surface where it is needed for thermal stability, while the bulk separator material maintains its original pore structure and ion conductivity. This localized approach ensures thermal protection without compromising overall ion migration capability.
3Productivity
If electrolyte injection is performed at high temperature or pressure to improve impregnability, then electrolyte penetration is enhanced, but deformation and internal short circuits occur
Solution Approach 1:
The separator surface is pre-modified with a hydrophilic coating layer before battery assembly and electrolyte injection. This preliminary action enhances the surface wettability and electrolyte affinity, allowing electrolyte to penetrate efficiently at normal temperatures and pressures without requiring extreme conditions that could cause deformation or short circuits.
Solution Approach 2:
The coating layer changes the surface energy and wettability parameters of the separator, making it more hydrophilic and electrolyte-compatible. This parameter modification enables efficient electrolyte impregnation under mild conditions while maintaining structural integrity and preventing internal short circuits.
4Productivity
If the separator is made more hydrophilic to improve electrolyte wettability, then electrolyte impregnability is enhanced, but air permeability may be compromised
Solution Approach 1:
The coating layer uses a composite of hydrophilic binder polymers (such as polyvinylidene fluoride, polyacrylonitrile, or carboxymethyl cellulose) and ceramic particles. The polymer provides hydrophilicity for electrolyte wettability while the ceramic particles maintain pore structure and air permeability, achieving both improved wettability and maintained permeability simultaneously.
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 achieves improved electrolyte impregnability and productivity while maintaining mechanical and heat resistance, ensuring balanced performance and extended battery lifespan.
Implementation Method 1
a hydrophilic polymer applied to a surface of the porous support through a solution including the hydrophilic polymer and a solvent
Implementation Method 2
the electrolyte permeates between the positive electrode, the negative electrode, and the separator by capillary force
Data Source
AI summary
The present disclosure relates to a separator and a method of manufacturing the separator. The separator includes a porous support and a hydrophilic polymer applied to the surface of the porous support through a solution including the hydrophilic polymer and a solvent, and satisfies the following Equation: 0.015≤(C*D)/(A*B)≤0.65, where A is a thickness (μm) of the porous support, B is an air permeability (Gurley, seconds/100 ml) of the porous support, C is a porosity (% by volume) of the porous support, and D is a content (% by weight) of the hydrophilic polymer in the solution.