Crosslinked Polyolefin Separator Balancing Meltdown and Transmittance
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Solution Overview
Problem
Existing 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 crosslinking, which controls the boiling point and retention time to enhance heat resistance and light transmittance, preventing die-drool and improving processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional crosslinked polyolefin separator manufacturing methods are used, then the separator achieves crosslinked structure, but die-drool phenomenon occurs and processability deteriorates
Solution Approach 1:
The patent introduces alkoxysilane with carbon-carbon double bonded groups in divided doses before extrusion, allowing preliminary grafting reactions to occur during the extrusion process. This preliminary action of introducing crosslinking agents in controlled amounts before final formation prevents die-drool while achieving the desired crosslinked structure in the final separator product
Solution Approach 2:
The patent changes the parameters of crosslinking agent introduction by using alkoxysilane with carbon-carbon double bonded groups instead of conventional crosslinking agents, and by controlling the dosing rate and timing during extrusion. This parameter change in the chemical structure and introduction method of the crosslinking agent prevents die-drool phenomenon while maintaining processability
2Temperature
If the separator structure is optimized for high meltdown temperature, then thermal stability improves, but light transmittance decreases
Solution Approach 1:
The patent changes the chemical structure of the crosslinking agent to alkoxysilane with carbon-carbon double bonded groups, which enables the formation of a crosslinked network that maintains higher light transmittance compared to conventional crosslinking methods. This parameter change in the crosslinking chemistry allows simultaneous achievement of high meltdown temperature and adequate light transmittance
3Temperature
If crosslinking density is increased to improve meltdown temperature, then thermal resistance improves, but die-drool phenomenon worsens
Solution Approach 1:
The patent introduces the crosslinking agent in divided doses during the extrusion process, allowing gradual grafting and crosslinking to occur. This controlled preliminary action prevents sudden gelation and die-drool phenomenon while still achieving the desired crosslinking density for high meltdown temperature in the final product
Solution Approach 2:
The patent changes the molecular structure of the crosslinking agent to include carbon-carbon double bonded groups in alkoxysilane, which react differently during extrusion compared to conventional crosslinking agents. This parameter change in the chemical structure allows for controlled crosslinking that achieves high meltdown temperature without causing die-drool phenomenon
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 improved meltdown temperature, light transmittance, and safety, while preventing die-drool phenomena and ensuring effective processability.
Implementation Method 1
introduction of alkoxysilane with a carbon-carbon double bonded group in divided doses to an extruder, followed by reactive extrusion
Implementation Method 2
crosslinking, which controls the boiling point and retention time to enhance heat resistance and light transmittance
Implementation Method 3
extracting a diluting agent from the extruded composition
Implementation Method 4
The sheet is thermally fixed
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.