UHMW Polyolefin Separator Pore Control for Fast-Charge Safety
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Solution Overview
Problem
Existing lithium-ion battery separators face challenges in achieving high ionic conductivity while maintaining safety, particularly in fast-charging applications, due to issues with pore structure and coating methods that either compromise strength or lead to short circuits.
Innovation Solution
A method for preparing an ultrahigh-molecular-weight polyolefin separator using specific particle sizes and processes, including the production of micrometer-grade sodium chloride particles, mixing with ultrahigh-molecular-weight polyethylene and white oil, extrusion, and controlled extraction and stretching to achieve optimal apertures for high conductivity and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the porosity of the basement membrane is increased and the degree of zigzag is reduced to improve lithium ion migration speed, then the ionic conductivity is improved, but the strength of the separator is reduced
Solution Approach 1:
The patent uses ultrahigh-molecular-weight polyethylene as a composite material with exceptional molecular weight (≥1 million), combining the mechanical strength of high-molecular-weight polymers with the ionic conductivity benefits of optimized pore structure. This composite approach allows achieving both high strength (≥50 gf puncture strength) and high ionic conductivity (≥1.8 mS/cm) simultaneously
Solution Approach 2:
The patent changes the critical parameter of molecular weight to ultrahigh levels (≥1 million), which fundamentally alters the material properties. This parameter change enables the separator to maintain high mechanical strength while accommodating the pore structure needed for fast lithium ion transport, resolving the contradiction between strength and ionic conductivity
2Reliability
If the median aperture is increased to improve lithium ion passage rate for fast charging, then the ionic conductivity is improved, but the safety is compromised due to increased risk of short circuit
Solution Approach 1:
The patent optimizes the aperture size parameter to a specific range (0.04 μm-1 μm median aperture, maximum aperture ≤1.2 μm). This precise parameter control allows sufficient lithium ion passage for fast charging while maintaining safety by preventing aperture enlargement that could lead to short circuits. The ultrahigh molecular weight material enables this tight control
Solution Approach 2:
The patent implements a controlled extraction process where sodium chloride particles are used as porogens that are systematically removed to create the desired pore structure. This feedback-controlled approach ensures apertures remain within the safe range while providing adequate ionic conductivity, preventing both under-performance and safety issues
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 resulting separator achieves a median aperture of 0.04 μm-1 μm, maximum aperture of no more than 1.2 μm, and a puncture strength of ≥50 gf, ensuring both high ionic conductivity (≥1.8 mS/cm) and enhanced safety performance.
Implementation Method 1
The ultrahigh-molecular-weight polyolefin separator has a median aperture of 0.04 μm-1 μm, a maximum aperture of no more than 1.2 μm
Implementation Method 2
a step of extraction: first placing the cast sheet obtained by the extrusion and the molding in a mixture of acetone and water for extraction
Implementation Method 3
The separator with a better electrolyte wetting capacity has higher ionic conductivity, which is more conducive to the transmission of the lithium ions
Implementation Method 4
subsequently performing ultrasonic treatment while cleaning off sodium chloride and a part of the white oil in pores
Data Source
AI summary
The present application provides an ultrahigh-molecular-weight polyolefin separator, including ultrahigh-molecular-weight polyethylene. ultrahigh-molecular-weight polyethylene has an average molecular weight of ≥1 million. The ultrahigh-molecular-weight polyolefin separator has a median aperture of 0.04 μm-1 μm, the maximum aperture of no more than 1.2 μm, and a puncture strength of ≥50 gf. Further, the present application further provides a method for preparing an ultrahigh-molecular-weight polyolefin separator. Because the polyolefin separator is safer than an ordinary non-woven separator, and has higher ionic conductivity and larger median aperture, the problems that an ordinary non-woven separator of a lithium-ion battery, although having a high lithium-ion passage rate, has a high degree of danger, and is prone to cause a short circuit of the battery are exactly solved.