Fluorine-Based Composite Electrolyte Membrane for Redox Flow Batteries
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Solution Overview
Problem
Conventional electrolyte membranes for vanadium-type redox flow batteries fail to simultaneously achieve low electric resistance, high current efficiency, and oxidative deterioration resistance, with existing membranes either having high electric resistance, poor ion permselectivity, or being prone to oxidative deterioration.
Innovation Solution
A fluorine-based microporous membrane impregnated with a polyelectrolyte polymer, specifically a perfluorocarbonsulfonic acid resin, is used as the electrolyte membrane, which has a structure that allows for high proton permeability, low electric resistance, and effective suppression of active substance ion permeation, while maintaining oxidative stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diaphragms are used to separate electrolyte solutions, then ion permselectivity is improved, but electric resistance increases and oxidative deterioration occurs
Solution Approach 1:
The patent employs a composite membrane structure combining a porous base material (such as PTFE or polyolefin) with a hydrophilic polymer coating layer. This composite structure integrates the mechanical strength and chemical resistance of the porous base material with the high ion permselectivity and low electric resistance of the hydrophilic polymer layer, thereby simultaneously improving ion permselectivity while reducing electric resistance and oxidative deterioration
Solution Approach 2:
The patent utilizes porous membranes as the base material, which allow free permeation of electrolyte solutions driven by ionic differential pressure and osmotic pressure. The porous structure provides low electric resistance pathways for ion transport while the hydrophilic polymer coating enhances ion permselectivity, resolving the contradiction between ion separation efficiency and electric resistance
2Object-affected harmful factors
If membrane thickness is reduced to lower electric resistance, then electric resistance decreases, but mechanical strength deteriorates and oxidative deterioration increases
Solution Approach 1:
The composite membrane structure allows the use of thin hydrophilic polymer coating layers for low electric resistance while the porous base material provides the necessary mechanical strength and oxidative resistance. The base material acts as a robust support that compensates for the reduced thickness of the active separation layer
Solution Approach 2:
The membrane design applies different material properties to different layers: the porous base material provides mechanical strength and chemical stability, while the thin hydrophilic polymer coating layer provides low electric resistance and high ion permselectivity. This local differentiation of material functions resolves the contradiction between thickness reduction for low resistance and maintaining mechanical strength
3Object-affected harmful factors
If hydrocarbon-based ion-exchange membranes are used to achieve low electric resistance, then electric resistance decreases, but oxidative deterioration resistance worsens
Solution Approach 1:
The patent combines a hydrocarbon-based porous base material (which provides low electric resistance) with a fluorine-based hydrophilic polymer coating layer (which provides high oxidative deterioration resistance). The fluorine-containing polymer is specifically chosen for its exceptional chemical stability and resistance to oxidative degradation in sulfuric acid electrolyte solutions, while the hydrocarbon base material maintains low electric resistance
Solution Approach 2:
The patent converts the inherent weakness of hydrocarbon-based materials (poor oxidative resistance) into a benefit by using them only for the structural base where mechanical strength is needed, while the fluorine-based coating layer handles the chemical environment exposure. The hydrocarbon base material's low cost and good processing properties are also utilized, turning potential drawbacks into advantages through strategic material allocation
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 electrolyte membrane achieves high current efficiency and oxidative deterioration resistance by ensuring low electric resistance and effective ion permselectivity, preventing ion group elimination and collapse, even under long-term use in sulfuric acid electrolyte solutions.
Implementation Method 1
the electrolyte membrane has high proton permeability and low electric resistance
Implementation Method 2
effective suppression of active substance ion permeation
Implementation Method 3
a fluorine-based microporous membrane impregnated with a polyelectrolyte polymer, specifically a perfluorocarbonsulfonic acid resin
Implementation Method 4
maintaining oxidative stability... preventing ion group elimination and collapse, even under long-term use in sulfuric acid electrolyte solutions
Data Source
Figure 1
AI summary
This redox flow secondary battery has an electrolyte tank (6) containing: a positive electrode cell chamber (2) containing a positive electrode (1) comprising a carbon electrode; a negative electrode cell chamber (4) containing a negative electrode (3) comprising a carbon electrode; and an electrolyte membrane (5) as a barrier membrane that separates/isolates the positive electrode cell chamber (2) and the negative electrode cell chamber (4). The positive electrode cell chamber (2) contains a positive electrode electrolyte containing an active substance, the negative electrode cell chamber (4) contains a negative electrode electrolyte containing an active substance, and the redox flow secondary battery charges and discharges on the basis of the change in valency of the active substances in the electrolytes. The electrolyte membrane (5) contains an ion exchange resin composition that is primarily a polyelectrolye polymer, and the electrolyte membrane (5) has a reinforcing material comprising a fluorine-based porous membrane.