Separator Coating Binder for Gel Electrolyte Adhesion in Li Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges with separator adhesion to gel polymer electrolytes, leading to reduced battery performance and safety due to internal short circuits and thermal instability, especially when using inorganic particles that are non-reactive with the electrolyte.
Innovation Solution
A separator with a coating layer containing an organic binder with ethylenically unsaturated groups, such as vinyl or acryloxy groups, is used to enhance adhesion with the gel polymer electrolyte through radical polymerization, forming a three-dimensional polymer network that improves mechanical strength and ion transfer properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If inorganic particles are used in the coating layer to improve thermal stability, then heat resistance is improved, but adhesion to gel polymer electrolyte deteriorates due to non-reactive nature
Solution Approach 1:
The coating layer is formed as a composite material comprising inorganic particles (such as Al2O3, SiO2, TiO2, or ZrO2) dispersed in a polymer binder matrix. This composite structure combines the thermal stability of inorganic particles with the adhesive properties of the polymer binder, allowing the separator to simultaneously achieve heat resistance and strong adhesion to the gel polymer electrolyte.
2Reliability
If polyethylene separator is used to achieve shutdown function, then safety shutdown is improved, but thermal stability deteriorates at temperatures above 150°C due to melting
Solution Approach 1:
The separator structure is designed with different functional zones: the base layer maintains the shutdown function with polyethylene or similar materials, while the coating layer applied on top provides enhanced thermal stability and mechanical strength. This local differentiation allows each layer to perform its specific function optimally without compromising the other.
Solution Approach 2:
The separator is constructed as a composite structure combining a polyethylene base layer (providing shutdown function at around 130°C) with a coating layer containing inorganic particles and polymer binder (providing thermal stability above 150°C). This composite architecture enables the separator to exhibit both shutdown capability and high-temperature stability.
3Reliability
If liquid electrolyte is used to achieve high ionic conductivity, then ion transfer is improved, but safety deteriorates due to combustion risk and thermal runaway
Solution Approach 1:
The patent employs a gel polymer electrolyte that forms a flexible, solid-like matrix replacing the liquid electrolyte. This gel structure maintains ionic conductivity while eliminating the combustion risks associated with liquid electrolytes, as the gelated polymer network confines the liquid electrolyte components and prevents their free movement and vaporization.
Solution Approach 2:
The gel polymer electrolyte acts as an intermediary between the liquid electrolyte and the solid polymer electrolyte. It combines the advantages of both: the ionic conductivity of liquid electrolytes and the safety/mechanical properties of solid polymers, thereby reducing combustion risk while maintaining performance.
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 and mechanical strength of the separator enhance the battery's output properties, lifespan, and safety by preventing internal short circuits and thermal runaway, while maintaining lithium ion conductivity and stability.
Implementation Method 1
the organic binder contains an ethylenically unsaturated group... forming a three-dimensional polymer network that improves mechanical strength
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.