Crosslinked Polyolefin Separator Substrate for Thermal Shrinkage Resistance
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Solution Overview
Problem
Lithium ion batteries face safety risks due to thermal shrinkage of polyolefin-based separator substrates, leading to potential short circuits and thermal runaway, and require improved manufacturing processes for enhanced stability and safety.
Innovation Solution
A separator substrate comprising a crosslinked polyolefin resin with silicon-containing organic groups and chromium, featuring uniform thickness and high heat resistance, achieved through a manufacturing process involving melt extrusion, stretching, and application of a thermal initiator and silane compound to form crosslink structures and grafting sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyolefin-based separator substrates are used, then manufacturing process is simplified, but thermal shrinkage occurs at high temperature causing safety issues
Solution Approach 1:
The patent applies composite materials by combining polyolefin resin with silane compounds to create a crosslinked structure. This composite approach maintains the ease of manufacturing polyolefin while adding thermal stability through the crosslinked network that resists thermal shrinkage at high temperatures.
Solution Approach 2:
The patent changes the physical and chemical parameters of the polyolefin resin by introducing crosslinked structures through silane compounds. This parameter change transforms the linear polyolefin chains into a three-dimensional crosslinked network, fundamentally altering the thermal behavior to prevent shrinkage while maintaining processability.
2Reliability
If separator substrate thickness is increased to prevent short circuits, then safety improves, but manufacturing precision and uniformity deteriorate
Solution Approach 1:
The patent changes the dimensional parameters by controlling the crosslinking degree and network density to achieve optimal thickness uniformity. The crosslinked structure allows for precise control of thermal shrinkage, maintaining uniform thickness at 0.5 μm or less standard deviation while providing adequate safety margin against short circuits.
3Reliability
If crosslinking is increased to improve heat resistance, then thermal stability improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies self-service by using silane compounds that automatically crosslink during the existing manufacturing process without requiring additional complex equipment or steps. The crosslinking occurs in-situ during production, allowing the material to self-organize into a thermally stable network while maintaining manufacturing simplicity.
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 solution enhances thickness uniformity, heat resistance, and electrolyte wettability, improving the stability and safety of electrochemical devices by reducing thermal shrinkage and preventing short circuits.
Implementation Method 1
a crosslink structure in the crosslinked polyolefin resin may include a structure resulting from radical polymerization reaction between vinyl groups through a thermal initiator
Implementation Method 2
the thermal initiator may include a peroxide-based compound, a persulfate-based compound, an azo-based compound or a mixture thereof
Implementation Method 3
drying and heat-setting the polymer sheet coated with the coating solution
Data Source
AI summary
A separator substrate, a separator comprising the same, and an electrochemical device comprising the same are provided. The separator substrate comprises a crosslinked polyolefin resin and chromium (Cr), wherein the crosslinked polyolefin resin comprises a silicon-containing organic group grafted to a polyolefin chain, a gel fraction of the separator substrate is 3% to 80%, a standard deviation (Δd) of thickness measured in at least 100 random points is 0.5 μm or less, and a number of spots having a long side length of 50 μm or more per m2 is 10 or less.