Balancing Cell Layout for Redox Flow Battery Side Reactions
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Solution Overview
Problem
Aqueous redox flow batteries, such as all-iron RFBs, face a technical challenge due to parasitic side reactions that lead to an imbalance in the state of charge, resulting in cell failure if not addressed.
Innovation Solution
The introduction of an electrochemical balancing cell with a single interface, utilizing a catalyst coated substrate to oxidize hydrogen gas and maintain protons in the negative electrolyte, eliminates the need for multiple membranes and reduces costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flow through cell with hydrogen gas chamber and positive electrolyte chamber is used for rebalancing, then the state of charge is balanced and protons are inserted back into the negative electrolyte, but a second membrane is required and one membrane must be highly conductive for proton transport, increasing cost
Solution Approach 1:
The patent combines the hydrogen gas chamber and positive electrolyte chamber into a single chamber, eliminating the need for a second membrane. The catalyst spans both phases within the same chamber, allowing proton insertion directly into the negative electrolyte without requiring separate compartments and multiple membranes.
Solution Approach 2:
The single chamber serves multiple functions: it acts as both the hydrogen gas chamber and the positive electrolyte chamber, and the catalyst performs both catalysis and membrane-like proton transport functions, reducing the overall component count and complexity.
2Reliability
If a flow through cell with hydrogen gas chamber and positive electrolyte chamber is used for rebalancing, then the state of charge is balanced and protons are inserted back into the negative electrolyte, but highly proton conductive membranes are required, increasing cost
Solution Approach 1:
The patent combines the hydrogen gas chamber and positive electrolyte chamber into a single chamber, eliminating the need for a second membrane. The catalyst spans both phases within the same chamber, allowing proton insertion directly into the negative electrolyte without requiring separate compartments and multiple membranes.
Solution Approach 2:
The patent replaces expensive highly proton conductive membranes with a catalyst that can be less expensive and potentially replaced more easily. The catalyst performs the proton transport function without requiring the high conductivity and durability specifications of specialized membranes.
3Reliability
If an interface is created across a membrane between positive electrolyte and hydrogen gas for rebalancing, then the state of charge is balanced, but protons migrate into the positive electrolyte instead of being returned to the negative electrolyte
Solution Approach 1:
The patent introduces a catalyst as an intermediary substance that facilitates the direct transfer of protons from the hydrogen gas phase to the negative electrolyte. The catalyst spans both phases and provides a pathway for protons to bypass the membrane interface, ensuring they are returned to the correct electrolyte compartment.
Solution Approach 2:
Instead of allowing protons to migrate through the membrane to the positive electrolyte (the conventional approach), the patent inverts the process by using a catalyst to directly insert protons back into the negative electrolyte from the hydrogen gas phase, reversing the unwanted proton migration pathway.
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 configuration effectively balances the state of charge of the positive electrolyte and the pH of the negative electrolyte, preventing cell failure and reducing operational costs by eliminating the requirement for highly proton conductive membranes.
Implementation Method 1
A catalyst spans the gaseous and liquid phases to create a series of triple interfaces between the catalyst, the gas, and the electrolyte. When the oxidation reaction occurs, the protons (H+) are carried directly into the negative electrolyte
Implementation Method 2
Buoyancy may be used to generate the gas-electrolyte interface
Implementation Method 3
an electrochemical balancing cell with a single interface, utilizing a catalyst coated substrate to oxidize hydrogen gas and maintain protons in the negative electrolyte
Data Source
AI summary
A redox flow battery with an electrochemical balancing cell having first and second chambers. The first chamber includes a catalyst coated substrate and the second chamber includes an electrode. Each receives an electrolyte from the redox flow battery. There is a single interface between the two chambers. The balancing cell reverses parasitic reactions in the first chamber that occur in the redox flow battery. The products of the reversed reactions are carried away from the electrochemical balancing cell and back to the redox flow battery in the electrolyte that carried the reactant to the first chamber. Also, processes for reversing a parasitic reaction in a redox flow battery.