Crosslinked Polyolefin Separator Processing to Prevent Die Drool
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Solution Overview
Problem
Existing methods for manufacturing crosslinked polyolefin separators in lithium secondary batteries face challenges in achieving high meltdown temperature, preventing die-drool phenomena, and ensuring high light transmittance, which are crucial for safety and processability.
Innovation Solution
A method involving controlled introduction of alkoxysilane with carbon-carbon double bonded groups in divided doses, along with a crosslinking catalyst and initiator, through reactive extrusion, followed by stretching, extraction, and thermal fixation, to create a crosslinked polyolefin separator with specific ratios and boiling points to enhance grafting and minimize direct polyolefin crosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If polyolefin, diluent, alkoxysilane, initiator and crosslinking catalyst are introduced at once to an extruder, then the manufacturing process is simple, but die-drool phenomenon occurs and processability deteriorates
Solution Approach 1:
The manufacturing process is segmented into two distinct stages: (1) introducing polyolefin, diluent, and alkoxysilane to the extruder, extruding to form a sheet, and (2) introducing initiator and crosslinking catalyst to the extruder, then extruding and heat-treating the sheet. This segmentation prevents die-drool phenomenon by separating the introduction timing of different materials, thereby improving processability while maintaining manufacturing simplicity.
2Ease of manufacture
If crosslinked polyolefin separator is manufactured by conventional methods, then the process is established, but light transmittance is insufficient and safety is compromised
Solution Approach 1:
The patent modifies the manufacturing parameters by controlling the introduction timing of materials (polyolefin, diluent, alkoxysilane, initiator, crosslinking catalyst) and optimizing heat treatment conditions (temperature and time). These parameter changes result in improved light transmittance of the crosslinked polyolefin separator while maintaining an established manufacturing process framework, thereby enhancing safety without abandoning conventional methods.
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 crosslinked polyolefin separator with improved meltdown temperature, reduced die-drool phenomena, and increased light transmittance, ensuring enhanced safety and processability.
Implementation Method 1
introducing polyolefin, a diluting agent, alkoxysilane containing a carbon-carbon double bonded group, an initiator and a crosslinking catalyst to an extruder, followed by mixing, and carrying out reactive extrusion
Implementation Method 2
crosslinking the thermally fixed porous membrane in the presence of water
Implementation Method 3
thermally fixing the porous membrane
Data Source
AI summary
The present disclosure relates to a crosslinked polyolefin separator, which shows 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, and a method for manufacturing the same. 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.