Crosslinked Polyolefin Separator With High Meltdown Temperature
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Solution Overview
Problem
Current methods for manufacturing crosslinked polyolefin separators for lithium secondary batteries face challenges in achieving high meltdown temperature and light transmittance, leading to safety concerns and processability issues such as die-drool phenomena and low shutdown temperatures.
Innovation Solution
A method involving the introduction of alkoxysilane with a carbon-carbon double bonded group in divided doses to an extruder, followed by reactive extrusion, molding, and thermal crosslinking, to create a crosslinked polyolefin separator with improved heat resistance and light transmittance, controlling the boiling points and introduction times of alkoxysilanes to prevent die-drool and enhance grafting ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If crosslinked polyolefin separator is manufactured using conventional methods, then the separator achieves basic insulation and ion conductivity, but the meltdown temperature is insufficient and light transmittance is low
Solution Approach 1:
The patent changes the chemical composition parameters by introducing silane-grafted polyethylene content (0.1-5 wt%) and controlling the grafting ratio (0.5-10 grafted units per 1000 carbon atoms). These parameter changes enable the separator to achieve a meltdown temperature of 200°C or higher while maintaining safety through controlled crosslinking density.
Solution Approach 2:
The patent creates a composite structure by grafting silane units onto the polyethylene backbone, forming a crosslinked network within the separator matrix. This composite approach combines the benefits of polyethylene's processability with silane crosslinking's high heat resistance, achieving both improved meltdown temperature and maintained safety.
2Ease of manufacture
If crosslinked polyolefin separator is manufactured using conventional methods, then the separator provides basic structural integrity, but processability issues occur due to die-drool phenomenon
Solution Approach 1:
The patent optimizes the silane content parameter (0.1-5 wt%) and controls the grafting ratio to prevent excessive crosslinking during extrusion. This parameter control eliminates the die-drool phenomenon while maintaining good processability, allowing the separator to be manufactured without the harmful drooling defects associated with conventional methods.
3Illumination intensity
If crosslinked polyolefin separator is manufactured using conventional methods, then the separator achieves basic porosity, but light transmittance remains low affecting shutdown temperature detection
Solution Approach 1:
The patent controls the silane-grafted polyethylene content (0.1-5 wt%) and grafting ratio (0.5-10 per 1000 carbon atoms) to optimize the crosslinking density. This results in a separator with 30% or more light transmittance in the visible range (380-700 nm), enabling accurate shutdown temperature detection while maintaining precise manufacturing control.
4Temperature
If alkoxysilane is introduced in large amounts to improve crosslinking, then meltdown temperature increases, but die-drool phenomenon occurs reducing processability
Solution Approach 1:
The patent optimizes the alkoxysilane content parameter to 0.1-5 wt% and controls the grafting ratio to 0.5-10 grafted units per 1000 carbon atoms. This optimized parameter range achieves sufficient crosslinking for high meltdown temperature (200°C or higher) while preventing die-drool phenomenon, thereby maintaining excellent processability.
Solution Approach 2:
The patent applies partial crosslinking rather than excessive crosslinking, using controlled amounts of silane-grafted polyethylene (0.1-5 wt%). This partial action approach provides enough crosslinking to achieve high meltdown temperature while avoiding the die-drool phenomenon that results from excessive crosslinking during extrusion.
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 produces a crosslinked polyolefin separator with increased meltdown temperature, improved safety, and high light transmittance, preventing die-drool phenomena and ensuring better processability and mechanical strength.
Implementation Method 1
thermal crosslinking, to create a crosslinked polyolefin separator with improved heat resistance
Implementation Method 2
enhance grafting ratios
Implementation Method 3
high light transmittance, The shutdown temperature may be determined by the light transmittance of the separator
Data Source
AI summary
A crosslinked polyolefin separator having an average value of light transmittance of 30% or more in a region of 380 nm to 700 nm, after four sides of the separator are fixed and allowed to stand at 130° C. for 30 minutes. A method for manufacturing the crosslinked polyolefin separator is also provided. The crosslinked polyolefin separator has a low shutdown temperature to provide improved safety. The crosslinked polyolefin separator also has a high meltdown temperature and is inhibited from die-drooling.