Coated Lithium Battery Separator for Low Resistance and Heat Shrinkage
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Solution Overview
Problem
Rechargeable lithium batteries face challenges with high membrane resistance and thermal shrinkage, which affect their capacity, stability, and lifetime.
Innovation Solution
A separator for lithium batteries is developed with a porous substrate and a coating layer containing a (meth)acryl-based binder and specific fillers, which includes a mixture of fluorine-based adhesive binders, providing low membrane resistance and low thermal shrinkage, enhancing bonding strength to electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional separator is used, then the battery can operate, but the membrane resistance is high which limits capacity
Solution Approach 1:
The separator comprises a polyolefin base layer and a coating layer with a specific composite structure. The coating layer contains inorganic filler particles (alumina, silica, boehmite) dispersed in a binder polymer matrix, creating a composite material that reduces membrane resistance while maintaining structural integrity and thermal stability.
Solution Approach 2:
The separator utilizes a porous structure throughout, with the base layer having porosity of 30-80% and the coating layer containing porous inorganic filler particles. This porous architecture facilitates lithium ion transport, reducing membrane resistance and enabling higher battery capacity.
2Reliability
If a conventional separator is used, then the battery can operate, but thermal shrinkage is high which reduces stability and lifetime
Solution Approach 1:
The coating layer is composed of inorganic filler particles (alumina, silica, boehmite) embedded in a binder polymer matrix. This composite structure provides thermal stability and prevents excessive shrinkage at elevated temperatures, with the inorganic particles acting as thermal anchors that maintain separator dimensions during thermal events.
Solution Approach 2:
The separator achieves low thermal shrinkage (6.5% or less at 150°C) by optimizing the composition ratios of binder polymer to filler, controlling coating layer thickness (1-20 μm), and selecting filler particles with specific properties. These parameter optimizations ensure the separator maintains dimensional stability under thermal stress.
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 separator improves the stability and lifetime of lithium batteries by reducing membrane resistance and thermal shrinkage, increasing bonding strength and heat resistance.
Implementation Method 1
The coating layer includes a heat-resistant layer including a binder and a filler... The binder includes a (meth)acryl-based binder including a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or a salt thereof
Implementation Method 2
The coating layer includes a heat-resistant layer including a binder and a filler... The filler includes a filler having a particle diameter D50 ranging from 250 nm to 350 nm
Implementation Method 3
an adhesive layer on the heat-resistant layer and including an adhesive binder... The adhesive binder includes a mixture of a fluorine-based adhesive binder having a hydroxyl group or a carboxylic acid group and a fluorine-based adhesive binder not having a hydroxyl group and a carboxylic acid group
Data Source
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AI summary
The present disclosure relates to a separator for a rechargeable lithium battery and a rechargeable lithium battery including the separator. The separator includes a porous substrate and a coating layer on a surface of the porous substrate. The coating layer includes a heat-resistant layer including a binder and a filler, and an adhesive layer including an adhesive binder on the heat-resistant layer. The binder includes a (meth)acryl-based binder including a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or a salt thereof, a second structural unit derived from hydroxyalkyl (meth)acrylate, and a third structural unit derived from (meth)acrylamido sulfonic acid or a salt thereof. The filler has a particle diameter D50 ranging from 250 nm to 350 nm. The adhesive binder includes a fluorine-based adhesive binder having a hydroxyl group or a carboxylic acid group and a fluorine-based adhesive binder not having a hydroxyl group and a carboxylic acid group.