Lithium Battery Separator Coating for Thermal Stability
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Solution Overview
Problem
Conventional rechargeable lithium batteries face issues with rapid deterioration, internal and external short circuits, and heat-related safety concerns due to the contraction and expansion of electrodes, which can lead to separator fusion and destruction.
Innovation Solution
A separator for rechargeable lithium batteries is developed with a porous substrate coated with a layer containing organic particles and a binder polymer, providing excellent heat resistance and improved adherence, manufactured using emulsion polymerization methods with specific monomers and silane-based compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional porous polyethylene separator is used, then the separator has excellent shutdown characteristic and low cost, but the separator is easily fused and destroyed when the battery is heated up, leading to short circuits
Solution Approach 1:
The patent applies composite materials by combining polyethylene microparticles with a copolymer matrix (comprising 70-90 wt% vinylene carbonate and 10-30 wt% fluoroethylene carbonate). This composite structure provides both the shutdown characteristic of polyethylene and enhanced heat resistance from the copolymer matrix, resolving the contradiction between shutdown performance and temperature stability.
Solution Approach 2:
The patent changes the chemical composition parameters of the separator material by introducing specific carbonate esters (vinylene carbonate and fluoroethylene carbonate) with defined weight ratios. This parameter modification raises the melting point and thermal stability while preserving the shutdown function, addressing the heat resistance issue.
2Ease of manufacture
If the separator is made from conventional materials, then the manufacturing cost is low, but the battery rapidly deteriorates and becomes hot during charge and discharge cycles
Solution Approach 1:
The patent modifies the chemical composition parameters by using commercially available carbonate esters in specific ratios (70-90 wt% vinylene carbonate, 10-30 wt% fluoroethylene carbonate). This parameter optimization improves battery stability and reduces deterioration during cycling while maintaining reasonable manufacturing costs through the use of established chemical processes.
3Quantity of substance
If the separator uses conventional polyethylene structure, then the pores can be easily impregnated by electrolyte solution, but the separator contracts and fuses when heated, causing internal and external short circuits
Solution Approach 1:
The patent creates a composite structure where polyethylene microparticles provide porosity for electrolyte impregnation, while the copolymer matrix (vinylene carbonate and fluoroethylene carbonate) provides thermal stability. This composite approach maintains electrolyte absorption capability while preventing thermal shrinkage and fusion.
Solution Approach 2:
The patent applies local quality by distributing polyethylene microparticles within the copolymer matrix, creating regions with different functions: the microparticles provide shutdown capability and porosity, while the continuous copolymer phase provides thermal stability and prevents overall contraction.
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 solution enhances the safety and manufacturing cost-effectiveness of rechargeable lithium batteries by reducing thermal shrinkage, improving heat resistance, and maintaining high charge and discharge efficiency and capacity retention.
Implementation Method 1
a coating layer on one or more sides of the porous substrate, the coating layer including organic particles and a binder polymer
Implementation Method 2
the binder may further include a silane-based compound
Data Source
AI summary
A separator for a rechargeable lithium battery includes a porous substrate; and a coating layer disposed on one or more sides of the porous substrate, the coating layer including organic particles and a binder polymer, wherein the organic particles include a material different from that of the binder polymer and the binder polymer is included in the coating layer in an amount in a range of 50 to 99 wt % based on the total amount of the coating layer, and a rechargeable lithium battery including the same.