Co-extruded Ion Exchange Membranes for Fuel Cells
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Solution Overview
Problem
Current proton exchange membranes used in fuel cells suffer from anisotropy and thickness limitations, leading to premature failure under humidity cycling and high ohmic resistance, which hinders efficient energy conversion.
Innovation Solution
A process involving co-extrusion of an ion exchange precursor resin with an incompatible polymer to form a multilayer film, allowing for the removal of the incompatible polymer layer and producing a thin, uniform ion exchange resin membrane with reduced anisotropy and improved dimensional stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If melt-casting extrusion process is used to produce ion exchange membranes, then manufacturing scalability and cost are improved, but membrane thickness cannot be reduced below 25 microns without compromising thickness uniformity
Solution Approach 1:
The membrane production process is segmented into two independent stages: first producing a support layer with optimal thickness and mechanical properties, then depositing the ion exchange membrane on top. This allows each layer to be optimized independently, enabling the ion exchange membrane to be made thinner than 25 microns while maintaining overall structural integrity and uniformity.
Solution Approach 2:
A support layer acts as an intermediary between the manufacturing process and the thin ion exchange membrane. This support layer provides the mechanical strength and dimensional stability needed to handle and process membranes thinner than 25 microns, enabling reduced thickness without compromising manufacturability.
2Ease of manufacture
If melt-casting extrusion process is used, then manufacturing cost is reduced, but anisotropy in membrane properties increases causing premature failure under humidity cycling
Solution Approach 1:
By separating the support layer and ion exchange membrane into distinct layers, the anisotropy-inducing extrusion process is applied only to the support layer. The ion exchange membrane can then be deposited using a different process that produces more isotropic properties, reducing overall membrane anisotropy while maintaining manufacturing efficiency.
Solution Approach 2:
Different regions of the membrane structure are assigned different functions and properties: the support layer provides mechanical strength and can tolerate anisotropy from extrusion, while the ion exchange membrane layer is optimized for isotropic performance and ion conductivity. This local differentiation resolves the contradiction between manufacturing ease and compositional stability.
3Reliability
If membrane thickness is reduced to lower ohmic resistance, then fuel cell performance is improved, but mechanical robustness and durability are compromised
Solution Approach 1:
The membrane system is segmented into a support layer that provides mechanical robustness and a thin ion exchange membrane layer that provides low ohmic resistance. This segmentation allows the functional requirements of strength and conductivity to be satisfied by different layers, enabling overall system reliability improvement.
Solution Approach 2:
The membrane assembly is constructed as a composite structure combining a support layer material optimized for mechanical properties with an ion exchange membrane material optimized for electrical conductivity and ion transport. This composite approach enables simultaneous achievement of robustness and low resistance.
Data Source
AI summary
An ion exchange resin membrane or an ion exchange precursor resin membrane having a thickness of 25 microns or less and having an orientation ratio of 1.5 or less; which may be produced by co-extruding an ion exchange precursor resin with an incompatible polymer to form a multilayer film having a layer of the ion exchange precursor resin supported on a layer of the incompatible polymer. The layer of incompatible polymer is then removed from the layer of ion exchange precursor resin to provide the ion exchange precursor resin membrane. The ion exchange precursor resin membrane may be converted to an ion exchange resin membrane by hydrolysis, and subsequent acidification if desired.