Battery Separator Coating for Gel Electrolyte Adhesion and Thermal Stability
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Solution Overview
Problem
Existing separators for lithium secondary batteries face issues with adhesion to gel polymer electrolytes, leading to deteriorated stability and safety due to internal short circuits and thermal runaway, especially when using inorganic particles without reactive organic binders.
Innovation Solution
A separator with a coating layer containing an organic binder with ethylenically unsaturated groups, which undergoes a polymerization reaction with oligomers in the gel polymer electrolyte, forming a three-dimensional polymer network to enhance adhesion and improve mechanical strength and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If inorganic particles are used as coating material on separator, then thermal stability is improved, but adhesion to gel polymer electrolyte deteriorates
Solution Approach 1:
The patent uses a composite coating layer comprising both inorganic particles (such as Al2O3, SiO2, TiO2, or ZrO2) and organic binder polymers (such as polyacrylonitrile, polyvinylidene fluoride, or carboxymethyl cellulose) on the separator surface. This composite structure combines the thermal stability of inorganic particles with the adhesive properties of organic polymers, resolving the contradiction between thermal stability and adhesion to gel polymer electrolyte.
2Use of energy by moving object
If liquid electrolyte is used, then ionic conductivity is improved, but safety deteriorates due to combustion risk
Solution Approach 1:
The patent employs gel polymer electrolyte which represents a phase transition from liquid to gel state. The gel polymer electrolyte maintains the ionic conductivity characteristics of liquid electrolytes while eliminating the combustion risk associated with liquid electrolytes, as the gel structure prevents volatile organic solvent evaporation and combustion.
3Ease of manufacture
If separator uses polyethylene (PE), then cost is reduced, but thermal resistance deteriorates above 130°C
Solution Approach 1:
The patent uses a composite structure where a polyethylene (PE) or polypropylene (PP) separator is coated with a layer containing inorganic particles and organic binder polymers. This composite structure maintains the cost-effectiveness and basic separation function of PE/PP separators while the inorganic-organic coating layer provides enhanced thermal stability above 130°C, preventing membrane rupture at elevated temperatures.
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 improved adhesion between the separator and gel polymer electrolyte reduces internal resistance, enhances lithium ion transfer, prevents internal short circuits, and increases the battery's output and lifespan while maintaining safety under extreme conditions.
Implementation Method 1
the organic binder contains an ethylenically unsaturated group... undergoes polymerization with oligomers in the gel polymer electrolyte to form a three-dimensional polymer network
Data Source
AI summary
The present invention relates to a separator for a secondary battery, the separator including a substrate and a coating layer formed on the surface of the substrate, wherein the coating layer includes an organic binder and inorganic particles, and the organic binder contains an ethylenically unsaturated group, and to a lithium secondary battery including the same.