Ion-Permeable Web-Reinforced Separator Duplex Impregnation
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Solution Overview
Problem
Existing ion-permeable separators for alkaline water electrolysis face challenges with chemical stability in strong alkaline media at high temperatures and limited wettability, and current manufacturing technologies are not scalable for large-scale production of smooth, symmetrical ion-permeable web-reinforced separators.
Innovation Solution
A duplex type impregnating apparatus is used to apply a dope simultaneously to both sides of an elongated porous web, followed by phase inversion and coagulation, allowing for the production of self-supporting ion-permeable web-reinforced separators with symmetrical structures and flat surfaces, reducing production costs and enabling large-scale automation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional coating methods are used to apply dope to porous web, then coating can be achieved, but the surfaces become uneven and cockling occurs
Solution Approach 1:
The coating apparatus is divided into two separate coating units, each with its own doctor blade, operating independently on opposite sides of the web. This segmentation allows precise control of each coating surface without interference, enabling flat surfaces while maintaining simple individual unit design
Solution Approach 2:
Both coating surfaces are treated under identical conditions with symmetric dope application and simultaneous drying. This equipotential approach ensures both surfaces reach the same flat state without differential stress that causes cockling, while using standard coating technology
2Manufacturing precision
If dope is applied to porous web without air gap, then coating efficiency increases, but uneven drying and surface defects occur
Solution Approach 1:
The web is pre-coated with dope while passing through the coating apparatus, then immediately enters a drying section with controlled air gap. This preliminary coating followed by controlled drying prevents solvent pooling and ensures uniform evaporation, achieving both surface uniformity and maintained productivity
Solution Approach 2:
A controlled air gap acts as an intermediary between the coating application and final drying stages. This air gap allows gradual solvent evaporation and uniform drying without direct contact heating, preventing surface defects while maintaining continuous web transport speed
3Manufacturing precision
If single-sided coating is used, then process simplicity is maintained, but symmetrical structure and flatness cannot be achieved
Solution Approach 1:
The coating system is segmented into two independent but symmetric coating units, each with its own dope reservoir, doctor blade, and drying section. This segmentation enables precise control of each side while maintaining overall symmetry, achieving flat surfaces without excessive complexity
Solution Approach 2:
While the apparatus appears symmetric, the design intentionally creates asymmetric control capabilities - each coating unit can be independently adjusted for dope flow rate, doctor blade pressure, and drying conditions. This controlled asymmetry allows optimization for symmetrical outcomes
4Reliability
If traditional separator materials are used, then manufacturing is simple, but chemical stability and wettability are insufficient
Solution Approach 1:
The invention changes the chemical parameters of the separator by using dope containing inorganic hydroxide particles (such as barium hydroxide) mixed with polymer binder. This parameter change provides superior chemical stability in alkaline media and enhanced wettability, while the continuous coating process keeps manufacturing complexity manageable
Solution Approach 2:
The separator is made as a composite material combining inorganic hydroxide particles with organic polymer binder in a dope solution. This composite structure provides both the chemical stability of inorganic materials and the processability of organic polymers, achieving high reliability without excessive manufacturing complexity
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 process results in ion-permeable web-reinforced separators with improved smoothness, reduced cockling, and enhanced ion conductivity, suitable for high-temperature alkaline water electrolysis, while allowing for cost-effective and efficient large-scale production.
Implementation Method 1
phase inversion of a binder-containing dope to provide the necessary porosity
Implementation Method 2
coagulation station providing for coagulation and washing of solvent from the resulting phase-inverted dope
Data Source
Figure 1
Figure 2
AI summary
An apparatus for producing an ion-permeable web-reinforced separator comprising a duplex type impregnating apparatus comprising two slots each with substantially vertical upper and lower slot faces for providing premetered substantially identical quantities of a dope simultaneously to either side of an elongated porous web, a transport means providing for substantially vertical downwards transport of said elongated porous web through said duplex impregnating apparatus and subsequent phase inversion, coagulation and washing stations, said phase inversion station providing for phase inversion of said dope and said coagulation station providing for coagulation and washing of solvent from the resulting phase-inverted dope, wherein there is an air gap between said duplex impregnating apparatus and said phase inversion station and wherein the distance between the lower faces of each impregnating apparatus is greater than the distances between the upper faces of each impregnating apparatus; a 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 to symmetric 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 steps (iv) and (v) are optionally performed simultaneously; and the separator obtainable therewith.