Porous Lithium Battery Separator Coating for Low Resistance and Shrinkage
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in maintaining high energy density, capacity, stability, and safety due to issues with thermal contraction and membrane resistance in the separator.
Innovation Solution
A separator for rechargeable lithium batteries is developed, comprising a porous substrate with a coating layer containing a (meth)acryl-based binder and a filler with specific particle diameters, along with an adhesive binder, which enhances bonding strength, reduces heat shrinkage, and maintains low membrane resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator is used in rechargeable lithium battery, then safety is improved by preventing thermal contraction, but membrane resistance increases which reduces battery capacity
Solution Approach 1:
The separator is designed with a porous structure having specific porosity (30-70%) and pore size (0.01-10 μm) to maintain ion permeability while providing mechanical stability. The porous substrate allows lithium ion transport through the separator without significant resistance, resolving the contradiction between safety and capacity.
Solution Approach 2:
The separator employs composite material structure combining porous substrate with coating layers containing specific polymers and additives. This composite approach provides both the thermal stability needed for safety and the controlled porosity required for low membrane resistance, enabling simultaneous improvement of both parameters.
2Strength
If coating layer is added to separator, then bonding strength and air permeability are improved, but heat shrinkage rate increases which reduces stability
Solution Approach 1:
The coating layer uses specific polymer compositions with controlled molecular weights and crosslinking densities to achieve optimal balance. By adjusting parameters such as polymer type, crosslinking degree, and coating thickness, the formulation achieves high bonding strength while maintaining low heat shrinkage rate through precise parameter optimization.
Solution Approach 2:
The separator structure employs different layers with specialized functions: the porous substrate provides mechanical support with controlled porosity, while the coating layers provide bonding functionality. This local differentiation allows each layer to optimize its specific property without compromising the other, achieving both high bonding strength and low heat shrinkage.
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 lithium battery capacity, stability, and safety by providing high bonding strength, low heat shrinkage, and reduced resistance, facilitating efficient lithium ion movement and improved air permeability.
Implementation Method 1
The separator improves lithium battery capacity, stability, and safety by providing high bonding strength, low heat shrinkage, and reduced resistance, facilitating efficient lithium ion movement
Implementation Method 2
an adhesive binder on the heat-resistant layer... increases the stability and lifetime of a rechargeable lithium battery by having a significantly low heat shrinkage rate... increases the stability of a rechargeable lithium battery by having desired or improved air permeability and high bonding strength
Implementation Method 3
The separator for a rechargeable lithium battery includes a porous substrate and a coating layer on at least one surface of the porous substrate... having desired or improved air permeability
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 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 filler having a particle diameter D50 ranging from about 250 nm to about 350 nm. The adhesive binder includes a fluorine-based homopolymer, and an interpenetrating polymer network (IPN) binder mixture of a fluorine-based cross-linked polymer and an acrylate-based cross-linked polymer.