Battery Separator Coating for Low Resistance and Heat Shrinkage
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Solution Overview
Problem
Rechargeable lithium batteries face challenges with high membrane resistance, heat shrinkage, and low bonding strength, which affect their capacity, stability, and lifetime.
Innovation Solution
A separator for lithium batteries featuring a porous substrate with a coating layer containing a (meth)acryl-based binder and a mixture of cubic and plate-shaped fillers, along with an adhesive binder, to enhance heat resistance, reduce membrane resistance, and improve bonding strength.
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 employs a composite structure consisting of a porous substrate combined with a coating layer containing inorganic filler particles (alumina, silica, or boehmite) dispersed in a binder polymer matrix. This composite material configuration reduces membrane resistance by providing ion conduction pathways while maintaining structural integrity, thereby improving battery capacity without compromising safety.
2Reliability
If a conventional separator is used, then the battery can operate, but heat shrinkage is high which reduces stability and lifetime
Solution Approach 1:
The separator utilizes a binder polymer with specifically controlled glass transition temperature (Tg) parameters, where the Tg is positioned between -50°C and 100°C. This parameter optimization, combined with the inorganic filler content ranging from 10-90 wt%, modifies the thermal behavior of the separator to minimize heat shrinkage at elevated temperatures, thereby enhancing battery stability and extending operational lifetime.
3Reliability
If a conventional separator is used, then the battery can operate, but bonding strength is low which reduces stability
Solution Approach 1:
The separator employs a porous substrate structure with controlled porosity that facilitates mechanical interlocking with electrode materials. The porous architecture, combined with the coating layer containing inorganic filler particles, increases the surface area and creates anchoring points that enhance bonding strength between the separator and electrodes, thereby improving overall battery stability.
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 achieves low membrane resistance, low heat shrinkage, and high bonding strength, thereby increasing the capacity, stability, and lifetime of the lithium battery.
Implementation Method 1
The separator may have low membrane resistance, high heat resistance, resulting in low heat shrinkage
Implementation Method 2
an adhesive layer on the heat-resistant layer and including an adhesive binder
Data Source
AI summary
Examples of the present disclosure include 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 at least one 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 includes a mixture of a cubic filler a plate-shaped filler. The adhesive binder includes a fluorine-based adhesive binder having a hydroxyl group or a carboxylic acid group.