Web-Reinforced Separator Coating via Vertical Impregnation
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Solution Overview
Problem
Current ion-permeable separators for alkaline water electrolysis face challenges such as poor chemical stability in strong alkaline mediums at high temperatures, limited wettability, and poor ionic conductivity, making them unsuitable for large-scale production and optimal performance.
Innovation Solution
A duplex type impregnating apparatus is used to apply a dope simultaneously to both sides of an elongated porous web, followed by immediate phase inversion and coagulation, eliminating the need for a leveling step and ensuring symmetrical, flat, and smooth ion-permeable web-reinforced separators with enhanced ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dope is applied to both sides of a porous web using conventional coating methods, then the separator can be produced, but the surfaces become non-flat requiring additional leveling steps that increase process complexity
Solution Approach 1:
The patent inverts the conventional coating approach by having the porous web pass through the dope in a vertical orientation between two impregnation heads, with the dope flowing downward under gravity. This inversion of the coating geometry allows the web to emerge flat and self-leveling, eliminating the need for additional leveling steps while maintaining symmetrical coating on both sides.
Solution Approach 2:
The patent transitions from horizontal coating to vertical coating by passing the web through the dope in the vertical direction. This dimensional change allows gravity to assist in the coating process and enables the web to drain excess dope uniformly, resulting in flat surfaces without requiring complex leveling mechanisms.
2Reliability
If asbestos is used as separator material, then chemical stability and wettability are achieved, but health risks and quality fall-off occur
Solution Approach 1:
The patent changes the material composition parameters by using alternative polymers (polyacrylonitrile, polyvinylidene fluoride, or their copolymers) instead of asbestos, while maintaining the required chemical stability and wettability properties through careful selection of polymer chemistry and dope formulation.
Solution Approach 2:
The patent employs composite material systems where the separator consists of a porous web reinforced with polymer dope, creating a composite structure that achieves the desired chemical stability and wettability without using harmful asbestos materials.
3Manufacturing precision
If the web is passed horizontally through coating devices, then coating can be applied, but the web position becomes unstable and coating uniformity is poor
Solution Approach 1:
The patent inverts the coating orientation from horizontal to vertical, allowing the web to pass through the dope under gravity. This inversion provides inherent stability to the web position and ensures uniform coating distribution without the positioning problems associated with horizontal coating methods.
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
This method enables the production of self-supporting, symmetrical, and flat ion-permeable web-reinforced separators with improved ionic conductivity, suitable for large-scale production and optimal performance in alkaline water electrolysis, reducing production costs and ensuring smoothness.
Implementation Method 1
subjecting said dope associated with said elongated porous web immediately after dope-impregnation to symmetric phase inversion with at least one non-solvent thereby forming a membrane
Implementation Method 2
said coagulation station providing for coagulation and washing of solvent from the resulting phase-inverted dope
Data Source
Figure 1
Figure 2
AI summary
Process comprising the steps of : (i) providing an elongated porous web, said elongated porous web comprising two outermost surfaces; (ii) transporting said elongated porous web downwards between two impregnating heads comprising two slots each with substantially vertical upper and lower slot faces substantially parallel to said elongated porous web providing simultaneously to both surfaces of said elongated porous web metered substantially identical quantities of a dope, comprising at least one membrane polymer and at least one solvent therefor; (iii) thereby impregnating said elongated porous web completely with said dope and providing substantially equally thick dope layers on each surface of said outermost surfaces of said elongated porous web with a thickness independent of the gap between one of said lower slot faces and the surface of said elongated porous web nearest thereto; (iv) subjecting said dope associated with said elongated porous web immediately after dope-impregnation to symetric phase inversion with at least one non-solvent thereby forming a membrane; and (v) removing residues of said at least one solvent for said at least one membrane polymer from said membrane thereby producing an ion-permeable web-reinforced separator, wherein said dope is shear-thinning, and the separator obtainable therewith.