Crosslinked Battery Separator Coating for Thermal Shrinkage Resistance
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in maintaining safety and structural integrity under heat exposure, particularly due to thermal shrinkage and shrinkage in the electrolyte, which can compromise battery performance and reliability.
Innovation Solution
A separator for lithium batteries comprising a porous substrate with a coating layer made from a crosslinked product of a (meth)acryl-based binder, aziridine-based crosslinking agent, carboxyalkyl cellulose, and filler, which provides improved adhesion and heat resistance, reducing shrinkage and enhancing binding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used in a rechargeable lithium battery, then the battery can operate, but the separator undergoes thermal shrinkage and shrinkage in electrolyte, compromising safety and structural integrity
Solution Approach 1:
The separator is constructed as a composite material consisting of a polyolefin base layer combined with a heat-resistant coating layer containing inorganic particles (such as alumina, silica, or boehmite) dispersed in a binder resin. This composite structure provides both the functional properties of the base separator and the thermal stability of the coating layer, preventing shrinkage and maintaining structural integrity under heat exposure.
2Reliability
If the separator structure is enhanced to prevent shrinkage, then safety improves, but the complexity of the separator structure increases
Solution Approach 1:
The heat-resistant coating layer is applied in advance to the base separator before the separator is assembled into the battery. This preliminary action ensures that the shrinkage-resistant properties are already in place before thermal or electrolyte exposure occurs, simplifying the overall design while maintaining safety.
Solution Approach 2:
The coating layer's glass transition temperature is specifically adjusted to be higher than the battery's maximum operating temperature through selection of appropriate binder resins and inorganic particles. This parameter change ensures the coating remains dimensionally stable under operating conditions without requiring complex structural modifications.
3Temperature
If a coating layer is added to the separator to improve heat resistance, then safety under heat exposure improves, but the manufacturing process becomes more complex
Solution Approach 1:
The coating layer is applied using a dip-coating or spray-coating method, replacing more complex mechanical lamination or bonding processes. This substitution simplifies the manufacturing workflow while achieving the desired heat-resistant properties through the formation of a uniform thin coating layer.
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 ensures low drying and electrolyte shrinkage, along with high binding strength, thereby improving the safety and reliability of lithium batteries under heat exposure.
Implementation Method 1
The coating layer includes a crosslinked product of a binder, a cross-linking agent, and a carboxyalkyl cellulose or a salt thereof, and a filler. The binder includes a (meth)acryl-based binder that includes a first structural unit derived from (meth)acryl amide and a second structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof. The crosslinking agent includes an aziridine-based crosslinking agent
Implementation Method 2
It may be desirable for the separator to retain the original shape thereof without thermal shrinkage in the electrolyte to improve the safety of the battery
Implementation Method 3
an adhesive layer located on one surface of the coating layer. The adhesive layer includes a (meth)acryl based adhesive binder
Data Source
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, a coating layer located on at least one surface of the porous substrate, and an adhesive layer located on one surface of the coating layer. The coating layer includes a crosslinked product of a binder, a cross-linking agent, and a carboxyalkyl cellulose or a salt thereof, and a filler. The binder includes a (meth)acryl-based binder that includes a first structural unit derived from (meth)acryl amide and a second structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof. The crosslinking agent includes an aziridine-based crosslinking agent, and the adhesive layer includes a (meth)acryl-based adhesive binder.