Systems and Methods for Rebalancing Redox Flow Battery Electrolytes
AssigneeEnerVault Corporation
InventorsAi Quoc PHAM, On Kok CHANG
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Abstract
Various methods of rebalancing electrolytes in a redox flow battery system include various systems using a catalyzed hydrogen rebalance cell configured to minimize the risk of dissolved catalyst negatively affecting flow battery performance. Some systems described herein reduce the chance of catalyst contamination of RFB electrolytes by employing a mediator solution to eliminate direct contact between the catalyzed membrane and the RFB electrolyte. Other methods use a rebalance cell chemistry that maintains the catalyzed electrode at a potential low enough to prevent the catalyst from dissolving.
Claims24
A rebalancing system configured to adjust a charge balance between a positive electrolyte and a negative electrolyte in a redox flow battery system, the rebalancing system comprising:
- an electrochemical reaction cell comprising a cathode chamber and an anode chamber separated from the cathode chamber by a separator membrane, the separator membrane having a coating containing a catalyst on a surface thereof;
- a hydrogen gas inlet in communication with the anode chamber;
- a redox flow battery negative electrolyte inlet in communication with the cathode chamber so as to allow a negative electrolyte to be flowed through the cathode chamber, the negative electrolyte containing Cr3+ ions and Cr2+ ions;
- a power supply having a first terminal and a second terminal, the first terminal connected to a first conductive element in the cathode chamber and the second terminal connected to a second conductive element in the anode chamber of the electrochemical reaction cell;
- and
- a controller configured to control a first flow of the negative electrolyte into the cathode chamber through the negative electrolyte inlet at a first rate, and to control a second flow of hydrogen gas into the anode chamber through the hydrogen gas inlet at a second rate, and to control the application of an electric current from the power supply to the first and second terminals, wherein the first rate, the second rate and the applied electric current are controlled so as to cause Cr3+ ions to be reduced to Cr2+ ions at one of:
- a controlled rate for a controlled period of time;
- or until a quantity of Cr2+ ions exceeds a threshold quantity.
A method of rebalancing Fe/Cr redox flow battery electrolytes, the method comprising:
- directing a negative electrolyte solution containing Cr3+ ions and Cr2+ ions through a cathode chamber of a rebalance cell, the cathode chamber having a first electrode;
- directing a quantity of hydrogen gas through a anode chamber of the rebalance cell, the anode chamber having a second electrode and being separated from the cathode chamber by a separator membrane having a catalyst-containing coating on a surface facing the anode chamber;
- applying an electric current to the rebalance cell;
- and
- controlling the quantity of hydrogen gas and the current applied to the rebalance cell so as to reduce at least some of the Cr3+ ions to Cr2+ ions according to a controlled reaction rate for a controlled period of time to rebalance the negative electrolyte solution.
Dependencies are inferred from the claim text.