UHMWPE Battery Separator Structure for Puncture and Compression Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing polyolefin microporous membranes using ultrahigh molecular weight polyethylene (UHMWPE) face challenges in quality as separators for electricity storage devices, including low gelling, molecular weight degradation, and reduced mechanical strength such as tensile and puncture strength.
Innovation Solution
A separator for electricity storage devices is formed using a mixed slurry of UHMWPE with a liquid plasticizer, specifying crystallinity through X-ray diffraction, and extrusion conditions to achieve a cross-sectional crystal orientation of 0.85 or greater, specific surface area of 1×10−2 nm² to 5×10−2 nm², and equivalent mean pore size of 50 nm to 150 nm, enhancing mechanical strength and resistance to compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If ultrahigh molecular weight polyethylene (UHMWPE) is used to produce polyolefin microporous membranes, then molecular weight degradation is reduced, but manufacturing difficulty increases due to casting challenges
Solution Approach 1:
The patent introduces a liquid paraffin as an intermediary substance to facilitate the casting of UHMWPE. The liquid paraffin acts as a medium that enables the high molecular weight polyethylene to be cast into membranes, overcoming the inherent casting difficulties of UHMWPE while preserving its molecular weight stability and resulting pore structure
2Strength
If polyethylene with high molecular weight (500,000 or greater) is used, then separator strength and shutdown properties are improved, but processing complexity increases
Solution Approach 1:
The patent changes the physical state parameter of the pore-forming agent from solid to liquid by using liquid paraffin instead of solid paraffin. This parameter change simplifies the processing of high molecular weight polyethylene, enabling easier mixing, casting, and pore formation while maintaining the separator strength and shutdown properties required for high-performance battery separators
3Manufacturing precision
If liquid paraffin is used as a pore-forming agent, then pore structure quality is improved, but extraction difficulty increases
Solution Approach 1:
The patent employs liquid paraffin as a temporary, disposable pore-forming agent that is easily extracted after casting. The liquid paraffin creates the desired pore structure during manufacturing and is then completely removed through simple extraction processes, leaving no residue that would interfere with separator performance or require complex removal procedures
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 provides a high-quality separator with improved tensile strength, puncture resistance, and compression resistance, maintaining membrane integrity under stress, particularly in the direction of thickness, suitable for high-capacity lithium ion batteries.
Implementation Method 1
specifying crystallinity through X-ray diffraction, and extrusion conditions to achieve a cross-sectional crystal orientation of 0.85 or greater
Implementation Method 2
specifying crystallinity through X-ray diffraction
Data Source
AI summary
A separator for an electricity storage device has a cross-sectional crystal orientation of 0.85 or greater, and/or a method for producing the separator for an electricity storage device comprises a step of using a continuous mixer under conditions with a temperature of 20° C. to 70° C., a shear rate of 100 to 400,000 seconds−1 and a residence time of 1.0 seconds to 60 seconds, for mixing of polyethylene-containing polyolefin powder with a plasticizer to produce a mixed slurry, a step of extruding the mixed slurry and cooling it to solidification to process it into a cast sheet, and a step of biaxially stretching the cast sheet to an area increase factor of 20 to 200.