Composite Fluoropolymer Vent for CO2 Selectivity Under Pressure
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Solution Overview
Problem
Existing vents for closed containers, particularly those used in flexible battery pouches, face a trade-off between selectivity for CO2 permeability and structural strength, often sacrificing selectivity for longevity, which can lead to pressure buildup and leakage issues.
Innovation Solution
A vent assembly comprising a protective fluoropolymer layer that permeates into a reinforcing layer, enhancing both CO2 permeability and structural strength, with a CO2 to water selectivity of at least 600 cm^3/g at 30°C and a permeability of at least 10,000 cm^3/(m^2 * 24h * atm, while maintaining resistance to pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the vent material is increased to improve structural strength, then the resistance to pressure and burst pressure are improved, but the CO2 permeability is reduced
Solution Approach 1:
The vent assembly uses a composite structure combining a fluoropolymer layer (PFA, FEP, PVF, PVDF, PCTFE, or ETFE) with a reinforcing layer (mesh or expanded polymer). The fluoropolymer layer provides CO2 permeability and selectivity, while the reinforcing layer provides structural strength. This composite approach allows the vent to maintain high CO2 permeability without requiring excessive material thickness, thus resolving the contradiction between permeability and pressure resistance.
Solution Approach 2:
The vent assembly distributes different functions to different layers: the fluoropolymer layer is optimized for gas permeability and selectivity, while the reinforcing layer is optimized for mechanical strength. This local specialization allows each layer to perform its function efficiently without compromising the other, enabling the vent to achieve both high CO2 permeability and resistance to pressure simultaneously.
2Reliability
If the selectivity of the vent material is increased to prevent water vapor ingress, then the CO2 to water selectivity is improved, but the structural strength and lifetime are reduced
Solution Approach 1:
The vent assembly combines a fluoropolymer layer with high CO2 to water selectivity (at least 600 cm3/g at 30°C) with a reinforcing layer that provides structural strength and durability. The fluoropolymer layer maintains excellent selectivity properties, while the reinforcing layer compensates for the inherent weakness of thin fluoropolymer layers, extending the vent's lifetime without sacrificing selectivity.
3Reliability
If the thickness of the fluoropolymer layer is increased to improve selectivity, then the CO2 to water selectivity is improved, but the CO2 permeability is reduced
Solution Approach 1:
The vent assembly uses a thin fluoropolymer layer (optimized for permeability) combined with a reinforcing layer. The thin fluoropolymer layer maintains high CO2 permeability, while the reinforcing layer provides the necessary structural support. This composite structure eliminates the need to increase fluoropolymer thickness to achieve selectivity, as the selectivity is maintained through material composition rather than thickness.
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 effectively retains selectivity while significantly increasing the vent's strength, allowing it to withstand pressure without compromising CO2 permeability, thus preventing leakage and ensuring the longevity of the closed container.
Implementation Method 1
the at least one protective fluoropolymer layer has a carbon dioxide (CO2) to water (H2O) selectivity of at least 600 cm3/g at 30°C and a permeability of at least 10,000 cm3/(m2 * 24h * atm)
Implementation Method 2
Such vents are required to be selective in the gasses that they allow to pass through them and typically are required to substantially prevent water vapour entering the closed container whilst allowing gasses generated during the lifetime of the closed container such as carbon dioxide to pass out of the closed container through the vent
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
A vent is provided herein for use in a closed container, the vent comprising at least one protective fluoropolymer layer and at least one reinforcing layer, wherein the at least one protective fluoropolymer layer at least partially permeates into the at least one reinforcing layer, wherein the at least one protective fluoropolymer layer has a carbon dioxide (CO2) to water (H2O) selectivity of at least 600 cm3/g at 30°C and a CO2 permeability of at least 10,000 cm3/(m2 * 24h * atm) at 30°C as measured using methods described herein.