PTFE Battery Membrane Biaxial Stretching Oxidative Stability
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Solution Overview
Problem
Current battery isolation membranes, made from materials like polyethylene and polypropylene, are not suitable for highly oxidative environments and degrade quickly, lacking the mechanical strength and stability required for long-term battery performance.
Innovation Solution
A biaxially-oriented expanded polytetrafluoroethylene microfiltration membrane is developed using a fishtail-type die extrusion, multi-pass ultrahigh-temperature and high-speed stretching, and heat treatment processes to achieve regular fiber arrangement, high porosity, and enhanced mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene or polypropylene membranes are used for battery isolation, then manufacturing cost is reduced, but the membrane degrades quickly in highly oxidative environments
Solution Approach 1:
The patent changes the material parameter from conventional polyethylene/polypropylene to polytetrafluoroethylene (PTFE), which has fundamentally different chemical properties including resistance to oxidation and reduction. This material substitution resolves the contradiction by providing both the required stability in oxidative environments and extended service life, while the cost issue is addressed through optimized processing methods.
Solution Approach 2:
The patent creates a composite structure by reinforcing PTFE membrane with specific fiber arrangements and structural configurations. This composite approach enhances the mechanical strength and durability of the PTFE membrane, further improving its service life and reliability in battery applications while maintaining the chemical stability advantages of PTFE.
2Manufacturing precision
If conventional extrusion methods are used, then manufacturing process is simple, but the membrane lacks regular fiber arrangement and has nodules
Solution Approach 1:
The patent divides the extrusion process into multiple stages with different functional zones within the die structure. The fishtail-type die is segmented into specific sections that control fiber orientation and distribution at different locations, enabling regular fiber arrangement while managing the complexity through modular process design.
Solution Approach 2:
The patent introduces biaxial stretching in addition to the conventional uniaxial extrusion process. This dimensional enhancement creates regular fiber arrangement in both machine and transverse directions, transforming the membrane structure from simple to highly organized, while the multi-pass approach manages process complexity systematically.
3Strength
If high stretching ratios are applied, then porosity and mechanical strength are improved, but membrane swelling increases
Solution Approach 1:
The patent applies different stretching ratios and heat treatment conditions to different regions and stages of the membrane processing. The multi-pass stretching uses progressively adjusted parameters, and heat treatment is applied at specific stages to locally control crystallinity and dimensional stability, preventing excessive swelling while maintaining high strength.
Solution Approach 2:
The patent systematically changes multiple parameters including stretching ratio, stretching speed, temperature, and heat treatment conditions to optimize the balance between porosity, strength, and dimensional stability. By adjusting these parameters in combination rather than singly, the patent achieves high tensile strength while controlling membrane swelling through precise parameter management.
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 membrane exhibits improved tensile strength, elastic modulus, and dimensional stability, reducing swelling and internal resistance, thus extending battery life and reducing material costs.
Implementation Method 1
a fishtail-type die extrusion, multi-pass ultrahigh-temperature and high-speed stretching
Implementation Method 2
multi-pass ultrahigh-temperature and high-speed stretching, and heat treatment processes
Data Source
Figure 1~2
Figure 3
AI summary
The present invention discloses an enhanced membrane for battery isolation, which is a biaxially-oriented expanded polytetrafluoroethylene microfiltration membrane, with a longitudinal tensile strength of 25 to 30 Mpa, a transverse tensile strength of 20 to 25 MPa, a longitudinal elastic modulus of 70 to 80 Mpa, a transverse elastic modulus of 50 to 60 Mpa, and a maximum longitudinal and transverse force of 3 to 4 N. The present invention also discloses a method of manufacturing an enhanced membrane for battery isolation, which comprises the steps of mixing-pressing-extruding-rolling-removing the lubricant-longitudinally stretching -heat treatment-cooling and shaping-transversely stretching-thermally shaping-cooling and shaping. The present invention has better dimensional stability and higher mechanical performance, and can significantly reduce the internal resistance of batteries and improve the performance of batteries, reduce the consumption of membrane materials, reduce the cost, and thus have a wide range of application.