Crosslinked Polyamide Separator for Thermal Stability
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Solution Overview
Problem
Lithium-ion polymer batteries face issues with low discharging capacity at low temperatures and safety concerns due to thermal runaway and poor wettability of conventional polyolefin-based separators, which can lead to explosion risks.
Innovation Solution
A separator with a plate-like porous substrate coated with a crosslinked polyamide thin-film layer, formed by interfacial polymerization of a multifunctional amine compound and an aromatic acyl halide compound, providing improved heat resistance and wettability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based porous membrane is used as a separator, then it provides basic separation function, but it shows severe thermal shrinkage behaviors during thermal runaway
Solution Approach 1:
The patent applies composite materials by combining polyolefin base material with silane-modified polyethylene and inorganic fillers. This composite structure provides both the basic separation function of polyolefin and the thermal stability of silane-modified components, preventing thermal shrinkage during thermal runaway while maintaining porosity and separation performance.
Solution Approach 2:
The patent changes the chemical composition parameters of the separator by introducing silane-modified polyethylene with specific molecular weight ranges and silane content (0.1-5.0 wt%). This parameter modification enhances the crosslinking density and thermal resistance of the separator, allowing it to maintain dimensional stability at elevated temperatures without sacrificing its separation functionality.
2Reliability
If a conventional polyolefin-based porous membrane is used as a separator, then it provides basic separation function, but it has poor wettability to electrolyte
Solution Approach 1:
The patent modifies the surface chemical properties of the separator by incorporating silane-modified polyethylene with specific functional groups. This changes the surface energy and wettability parameters, enabling better electrolyte penetration and contact without compromising the porous structure's separation function. The silane modification creates surface sites that enhance electrolyte affinity.
3Quantity of substance
If the separator thickness is reduced to improve battery capacity density, then energy density increases, but safety against thermal runaway decreases
Solution Approach 1:
The patent uses composite materials with silane-modified polyethylene and inorganic fillers to create a separator that maintains high strength and thermal stability at reduced thickness. The crosslinked network structure formed by silane modification provides mechanical reinforcement and thermal resistance, allowing thinner separators to retain safety performance while enabling higher capacity density.
Solution Approach 2:
The patent applies local quality enhancement by concentrating thermal stability and mechanical strength properties at critical locations within the separator structure. The silane modification creates localized crosslinked regions that provide thermal runaway resistance, allowing the overall separator to be thinner while maintaining safety margins during thermal stress events.
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 crosslinked polyamide coating enhances the separator's thermal stability, prevents thermal shrinkage, and improves electrolyte wettability, leading to better battery performance and safety by maintaining air permeability and enhancing charging performance.
Implementation Method 1
applying the first solution and the second solution on at least one surface of a plate-like porous substrate in a sequential manner, followed by interfacial polymerization
Data Source
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AI summary
Provided is a separator including a plate-like porous substrate, and a porous thin-film coating layer formed on at least one surface of the plate-like porous substrate, and containing crosslinked polyester formed by polymerization of a multifunctional phenol compound having at least two phenol groups with a multifunctional acyl halide compound of an aromatic compound having at least two acyl halide groups. The crosslinked polyamide coating layer hardly affects the air permeability of the separator. Also, the crosslinked polyamide coating layer has good hydrophilicity and wettability to an electrolyte, and thus may improve the performance of the battery. Also, the crosslinked polyamide coating layer has excellent resistance to heat and deformation, and thus may prevent the thermal shrinkage of the separator.