UV-Crosslinked Coated Separator for High-Heat Lithium-Ion Batteries
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Solution Overview
Problem
Existing lithium-ion battery separators exhibit unsatisfactory heat resistance, which hinders their performance and development in applications such as hybrid electric vehicles and energy storage.
Innovation Solution
A novel preparation method involving a ceramic layer coated with an adhesive polymer resin containing a controlled amount of photoinitiator, followed by UV crosslinking, optimizes the heat resistance and breakage temperature of the separator by ensuring sufficient crosslinking without affecting surface resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the photoinitiator content in the coating liquid is increased to improve crosslinking efficiency and heat resistance, then the breakage temperature is improved, but the surface resistance of the separator is adversely affected
Solution Approach 1:
The patent optimizes the photoinitiator content parameter to a specific range (0.08-1.0 wt%) in the coating liquid. This parameter change ensures sufficient crosslinking reaction for high breakage temperature (above 180°C) while controlling the photoinitiator amount to prevent excessive surface resistance, thus resolving the technical contradiction between heat resistance and surface resistance.
Solution Approach 2:
The patent applies different photoinitiator concentrations to different regions: the coating liquid contains photoinitiator at 0.08-1.0 wt% for crosslinking, while the adhesive coating layer on the separator surface maintains photoinitiator content at 0.05-0.3 wt%. This local quality differentiation ensures adequate crosslinking in the bulk while minimizing surface resistance impact.
2Reliability
If the photoinitiator content is too low to ensure sufficient crosslinking, then the heat resistance is insufficient, but increasing it improves crosslinking efficiency
Solution Approach 1:
The patent establishes an optimal parameter range for photoinitiator content (0.08-1.0 wt% in coating liquid, 0.05-0.3 wt% in adhesive coating layer) that simultaneously achieves sufficient crosslinking efficiency and high heat resistance. This parameter optimization ensures breakage temperature exceeds 180°C while maintaining effective photoinitiation during manufacturing.
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 method results in a separator with ultra-high heat resistance, thermal shrinkage rate less than 5% at 150°C, and a breakage temperature above 180°C, enhancing safety and performance.
Implementation Method 1
the photoinitiator can well penetrate into separator substrate layers (a ceramic layer and a membrane) after the coating liquid is coated on the membrane to ensure that enough reactive free radicals are produced by the photoinitiator in the membrane, the ceramic layer, and a combined interface layer to allow sufficient photoinitiation efficiency and crosslinking degree
Data Source
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Figure 6B~6C
AI summary
The present disclosure provides a coating slurry, a coated separator, a preparation method of the coated separator, and a battery including the coated separator. The coating slurry includes: a solvent, an adhesive polymer resin, and a photoinitiator, where a weight proportion of the photoinitiator in the coating slurry is 0.08 wt% to 1.0 wt%; and the adhesive polymer resin includes one or a combination of two or more of a polyvinylidene fluoride (PVDF)-based adhesive polymer resin, a polyimide (PI), a polyetherimide (PEI), and polymethylmethacrylate (PMMA). When the weight proportion of the photoinitiator in the coating slurry is controlled at 0.08 wt% to 1.0 wt%, the photoinitiator can well penetrate into separator substrate layers after the coating slurry is coated on a membrane to ensure that enough reactive free radicals are produced by the photoinitiator in the membrane, a ceramic layer, and a combined interface layer to allow sufficient photoinitiation efficiency and crosslinking degree, which ensures a complete crosslinking effect of an entire surface of a separator and greatly improves a breakage temperature of a separator. In addition, when the weight proportion of the photoinitiator in the coating slurry is controlled in the above range, a content of the photoinitiator remaining in an adhesive coating layer will not be too high, such that the photoinitiator will not affect a surface resistance of a separator and thus will not affect an interfacial resistance of a battery.