EP4348742A1 - Cellule de rééquilibrage pour système de batterie à flux redox - Google Patents

Cellule de rééquilibrage pour système de batterie à flux redox

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Publication number
EP4348742A1
EP4348742A1 EP22843035.1A EP22843035A EP4348742A1 EP 4348742 A1 EP4348742 A1 EP 4348742A1 EP 22843035 A EP22843035 A EP 22843035A EP 4348742 A1 EP4348742 A1 EP 4348742A1
Authority
EP
European Patent Office
Prior art keywords
electrolyte
electrode
cell
rebalancing
electrode assembly
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22843035.1A
Other languages
German (de)
English (en)
Inventor
Sean KISSICK
Yang Song
Craig Evans
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ESS Technology Inc
ESS Tech Inc
Original Assignee
ESS Technology Inc
ESS Tech Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ESS Technology Inc, ESS Tech Inc filed Critical ESS Technology Inc
Publication of EP4348742A1 publication Critical patent/EP4348742A1/fr
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0662—Treatment of gaseous reactants or gaseous residues, e.g. cleaning
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
    • H01M8/2425—High-temperature cells with solid electrolytes
    • H01M8/2432—Grouping of unit cells of planar configuration
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/2465—Details of groupings of fuel cells
    • H01M8/2483—Details of groupings of fuel cells characterised by internal manifolds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/249—Grouping of fuel cells, e.g. stacking of fuel cells comprising two or more groupings of fuel cells, e.g. modular assemblies
    • H01M8/2495—Grouping of fuel cells, e.g. stacking of fuel cells comprising two or more groupings of fuel cells, e.g. modular assemblies of fuel cells of different types
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04186—Arrangements for control of reactant parameters, e.g. pressure or concentration of liquid-charged or electrolyte-charged reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04276—Arrangements for managing the electrolyte stream, e.g. heat exchange
    • H01M8/04283—Supply means of electrolyte to or in matrix-fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • H01M8/184—Regeneration by electrochemical means
    • H01M8/188—Regeneration by electrochemical means by recharging of redox couples containing fluids; Redox flow type batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • FIELD [0002] The present description relates generally to systems for rebalancing cells for use in redox flow battery systems and methods for operating such rebalancing cells.
  • Redox flow batteries are suitable for grid-scale storage applications due to their capability for scaling power and capacity independently, as well as for charging and discharging over thousands of cycles with reduced performance losses in comparison to conventional battery technologies.
  • An all-iron hybrid redox flow battery is particularly attractive due to incorporation of low-cost, earth-abundant materials.
  • iron redox flow batteries IFBs
  • IFBs iron redox flow batteries
  • the IFB may include a positive (redox) electrode where a redox reaction occurs and a negative (plating) electrode where ferrous iron (Fe 2+ ) in the electrolyte may be reduced and plated.
  • Various side reactions may compete with the Fe 2+ reduction, including proton reduction, iron corrosion, and iron plating oxidation: H + + e- ⁇ 1 ⁇ 2H2 (proton reduction) (1) Fe 0 + 2H + ⁇ Fe 2+ + H2 (iron corrosion) (2) 2Fe 3+ + Fe 0 ⁇ 3Fe 2+ (iron plating oxidation) (3)
  • IFB cycling capabilities may be limited by available iron plating on the plating electrode.
  • Exemplary attempts to ameliorate iron plating loss have focused on catalytic electrolyte rebalancing to address hydrogen (H2) gas generation from equations (1) and (2) and electrolyte charge imbalances (e.g., excess Fe 3+ ) from equation (3) and ion crossover via equation (4): Fe 3+ + 1 ⁇ 2H2 ⁇ Fe 2+ + H + (electrolyte rebalancing) (4) [0005]
  • electrolyte rebalancing may be realized via a trickle bed or jelly roll reactor setup, wherein the H 2 gas and the electrolyte may be contacted at catalyst surfaces for carrying out the electrolyte rebalancing reaction of equation (4).
  • lower Fe 3+ reduction rates of such setups may be undesirable for higher performance applications.
  • a fuel cell setup may similarly contact the H 2 gas and the electrolyte at catalyst surfaces while applying a direct current (DC) across positive and negative electrode pairs.
  • DC direct current
  • reliability issues may arise in fuel cells as a result of inadvertent reverse current spikes interrupting DC flow.
  • a rebalancing cell for a redox flow battery including a cell enclosure, a hydrogen gas inlet port through which H2 gas is flowed into the cell enclosure, an electrolyte inlet port through which an electrolyte is flowed into the cell enclosure, an electrolyte outlet port through which the electrolyte is expelled from the cell enclosure, a stack of electrode assemblies enclosed by the cell enclosure, each electrode assembly of the stack of electrode assemblies including a negative electrode in face- sharing contact with a flow field configuration, and a sloped support coupled to the cell enclosure.
  • the negative and positive electrodes in each electrode assembly of the stack of electrode assemblies may be electrically conductive and in face-sharing contact with one another.
  • no electric current may be directed away from the rebalancing cell.
  • electrolyte rebalancing in the rebalancing cell may be driven via internal electrical shorting of interfacing pairs of the positive and negative electrodes therein.
  • each electrode assembly of the stack of electrode assemblies may be electrically decoupled from one another, such that no reverse electric current may be driven from one electrode assembly through the stack of electrode assemblies and degrade other electrode assemblies.
  • internal electrical shorting of the interfacing pairs of the positive and negative electrodes may reduce electrical resistance relative to non- internally shorted electrode pairs and thereby increase respective redox reaction rates at the positive and negative electrodes.
  • a cell potential of each electrode assembly may be concomitantly reduced, decreasing side reaction rates (e.g., rates of the reactions of equations (1)- (3)) therewith. In this way, both useful life may be prolonged and electrochemical performance may be enhanced in the rebalancing cell relative to a non-internally shorted cell.
  • FIG.1 shows a schematic diagram of an example redox flow battery system including a battery cell with redox and plating electrodes fluidically coupled to respective rebalancing reactors.
  • FIGS. 2A and 2B show perspective views of a rebalancing cell including a stack of internally shorted electrode assemblies.
  • FIG.3 shows an exploded view of an electrode assembly for the rebalancing cell of FIGS.2A and 2B.
  • FIGS. 4A and 4B show a cross-sectional view and a magnified inset view, respectively, of H2 gas flow in the rebalancing cell of FIGS.2A and 2B.
  • FIGS.5A-5D show schematic views of respective exemplary flow field configurations for convecting H 2 gas across negative electrodes of a rebalancing cell, such as the rebalancing cell of FIGS.2A and 2B.
  • FIGS. 6A and 6B show a cross-sectional view and a magnified inset view, respectively, of electrolyte flow in the rebalancing cell of FIGS.2A and 2B.
  • FIGS.7A and 7B show perspective views of electrolyte flow in an exemplary electrode assembly of a rebalancing cell, such as the rebalancing cell of FIGS.2A and 2B.
  • FIGS.8A-8C show perspective views of an exemplary flow field plate of an electrode assembly of a rebalancing cell, such as the rebalancing cell of FIGS.2A and 2B.
  • FIG.8D shows a cross-sectional view of the flow field plate of FIGS.8A-8C.
  • FIGS.9A and 9B show perspective views of an exemplary sloped support for tilting a cell enclosure of a rebalancing cell, as the rebalancing cell of FIGS.2A and 2B.
  • FIG. 10 shows a plot of Fe 3+ reduction rate as a function of a total amount of Fe 3+ reduced for three exemplary rebalancing cells in respective all-iron hybrid redox flow battery systems.
  • FIG.11 shows a flow chart of a method for operating a rebalancing cell including a stack of internally shorted electrode assemblies.
  • DETAILED DESCRIPTION [0021] The following description relates to systems and methods for a rebalancing cell driven via internal electrical shorting of electrode assemblies included therein.
  • the rebalancing cell may be fluidically coupled to an electrolyte subsystem of a redox flow battery.
  • the redox flow battery is depicted schematically in FIG.1 with an integrated multi- chambered tank having separate positive and negative electrolyte chambers.
  • the redox flow battery may be an all-iron flow battery (IFB) utilizing iron redox chemistry at both a positive (redox) electrode and the negative (plating) electrode of the IFB.
  • the electrolyte chambers may be coupled to one or more battery cells, each cell including the positive and negative electrodes. Therefrom, electrolyte may be pumped through positive and negative electrode compartments respectively housing the positive and negative electrodes.
  • the redox flow battery may be a hybrid redox flow battery.
  • Hybrid redox flow batteries are redox flow batteries which may be characterized by deposition of one or more electroactive materials as a solid layer on an electrode (e.g., the negative electrode).
  • Hybrid redox flow batteries may, for instance, include a chemical species which may plate via an electrochemical reaction as a solid on a substrate throughout a battery charge process. During battery discharge, the plated species may ionize via a further electrochemical reaction, becoming soluble in the electrolyte.
  • a charge capacity e.g., a maximum amount of energy stored
  • the redox flow battery may be limited by an amount of metal plated during battery charge and may accordingly depend on an efficiency of the plating system as well as volume and surface area available for plating.
  • electrolytic imbalances in the redox flow battery may result from numerous side reactions competing with desired redox chemistry, including hydrogen (H 2 ) gas generating reactions such as proton reduction and iron corrosion: H + + e- ⁇ 1 ⁇ 2H2 (proton reduction) (1) Fe 0 + 2H + ⁇ Fe 2+ + H 2 (iron corrosion) (2) and charge imbalances from excess ferric iron (Fe 3+ ) generated during oxidation of iron plating: 2Fe 3+ + Fe 0 ⁇ 3Fe 2+ (iron plating oxidation) (3) The reactions of equations (1) to (3) may limit iron plating and thereby decrease overall battery capacity.
  • hydrogen (H 2 ) gas generating reactions such as proton reduction and iron corrosion: H + + e- ⁇ 1 ⁇ 2H2 (proton reduction) (1) Fe 0 + 2H + ⁇ Fe 2+ + H 2 (iron corrosion) (2) and charge imbalances from excess ferric iron (Fe 3+ ) generated during oxidation of iron plating: 2Fe 3+ + Fe 0
  • electrolyte rebalancing may be leveraged to both reduce Fe 3+ and eliminate excess H2 gas via a single redox reaction: Fe 3+ + 1 ⁇ 2H2 ⁇ Fe 2+ + H + (electrolyte rebalancing) (4)
  • Fe 3+ reduction rates sufficient for relatively high performance applications may be reliably achieved via a rebalancing cell, such as the exemplary rebalancing cell of FIGS.2A and 2B, including a stack of internally shorted electrode assemblies, such as the exemplary electrode assembly of FIG.3.
  • FIGS.4A and 4B depict aspects of H 2 gas flow in the rebalancing cell, where the H 2 gas may be convected across negative electrodes of the internally shorted electrode assemblies via flow field plates, such as the exemplary flow field plate of FIGS.8A-8D, including respective flow field configurations, such as the exemplary flow field configurations of FIGS.5A-5D.
  • FIGS.6A-7B depict aspects of electrolyte flow in the rebalancing cell, where the electrolyte may be distributed across positive electrodes of the internally shorted electrode assemblies via a combination of gravity feeding and capillary action (additionally or alternatively, and similar to convection of the H 2 gas across the negative electrodes, the electrolyte may be convected across the positive electrodes via flow field plates, such as the exemplary flow field plate of FIGS. 8A-8D, including respective flow field configurations, such as the exemplary flow field configurations of FIGS. 5A-5D).
  • flow field plates such as the exemplary flow field plate of FIGS. 8A-8D, including respective flow field configurations, such as the exemplary flow field configurations of FIGS. 5A-5D).
  • gravity feeding may be assisted by coupling of a sloped support, such as the exemplary sloped support of FIGS.9A and 9B, to a cell enclosure of the rebalancing cell, such that the cell enclosure may rest on an incline with respect to a direction of gravity.
  • a sloped support such as the exemplary sloped support of FIGS.9A and 9B
  • FIG. 11 plots Fe 3+ reduction rates as a function of a total amount of Fe 3+ reduced during operation of exemplary rebalancing cells, indicating increased Fe 3+ reduction for rebalancing cells including internally shorted electrode assemblies.
  • a negative electrode 26 may be referred to as a plating electrode and a positive electrode 28 may be referred to as a redox electrode.
  • a negative electrolyte within a plating side (e.g., a negative electrode compartment 20) of a redox flow battery cell 18 may be referred to as a plating electrolyte, and a positive electrolyte on a redox side (e.g., a positive electrode compartment 22) of the redox flow battery cell 18 may be referred to as a redox electrolyte.
  • “Anode” refers to an electrode where electroactive material loses electrons and “cathode” refers to an electrode where electroactive material gains electrons.
  • the negative electrolyte gains electrons at the negative electrode 26, and the negative electrode 26 is the cathode of the electrochemical reaction.
  • the negative electrolyte loses electrons, and the negative electrode 26 is the anode of the electrochemical reaction.
  • the negative electrolyte and the negative electrode 26 may be respectively referred to as an anolyte and the anode of the electrochemical reaction
  • the positive electrolyte and the positive electrode 28 may be respectively referred to as a catholyte and the cathode of the electrochemical reaction.
  • the negative electrolyte and the negative electrode 26 may be respectively referred to as the catholyte and the cathode of the electrochemical reaction, while the positive electrolyte and the positive electrode 28 may be respectively referred to as the anolyte and the anode of the electrochemical reaction.
  • the terms “positive” and “negative” are used herein to refer to the electrodes, electrolytes, and electrode compartments in redox flow battery systems.
  • One example of a hybrid redox flow battery is an all-iron redox flow battery (IFB), in which the electrolyte includes iron ions in the form of iron salts (e.g., FeCl2, FeCl3, and the like), where the negative electrode 26 includes metal iron.
  • IOB all-iron redox flow battery
  • ferrous iron (Fe 2+ ) gains two electrons and plates as iron metal (Fe 0 ) onto the negative electrode 26 during battery charge, and Fe 0 loses two electrons and re-dissolves as Fe 2+ during battery discharge.
  • Fe 2+ loses an electron to form ferric iron (Fe 3+ ) during battery charge, and Fe 3+ gains an electron to form Fe 2+ during battery discharge.
  • the electrochemical reaction is summarized in equations (5) and (6), where the forward reactions (left to right) indicate electrochemical reactions during battery charge, while the reverse reactions (right to left) indicate electrochemical reactions during battery discharge: Fe 2+ + 2e- ⁇ Fe 0 -0.44 V (negative electrode) (5) Fe 2+ ⁇ 2Fe 3+ + 2e- +0.77 V (positive electrode) (6) [0028] As discussed above, the negative electrolyte used in the IFB may provide a sufficient amount of Fe 2+ so that, during battery charge, Fe 2+ may accept two electrons from the negative electrode 26 to form Fe 0 and plate onto a substrate.
  • the plated Fe 0 may lose two electrons, ionizing into Fe 2+ and dissolving back into the electrolyte.
  • An equilibrium potential of the above reaction is -0.44 V and this reaction therefore provides a negative terminal for the desired system.
  • the electrolyte On the positive side of the IFB, the electrolyte may provide Fe 2+ during battery charge which loses an electron and oxidizes to Fe 3+ .
  • Fe 3+ provided by the electrolyte becomes Fe 2+ by absorbing an electron provided by the positive electrode 28.
  • An equilibrium potential of this reaction is +0.77 V, creating a positive terminal for the desired system.
  • the IFB may provide the ability to charge and recharge electrolytes therein in contrast to other battery types utilizing non-regenerating electrolytes.
  • Charge may be achieved by respectively applying an electric current across the electrodes 26 and 28 via terminals 40 and 42.
  • the negative electrode 26 may be electrically coupled via the terminal 40 to a negative side of a voltage source so that electrons may be delivered to the negative electrolyte via the positive electrode 28 (e.g., as Fe 2+ is oxidized to Fe 3+ in the positive electrolyte in the positive electrode compartment 22).
  • the electrons provided to the negative electrode 26 may reduce the Fe 2+ in the negative electrolyte to form Fe 0 at the (plating) substrate, causing the Fe 2+ to plate onto the negative electrode 26.
  • Discharge may be sustained while Fe 0 remains available to the negative electrolyte for oxidation and while Fe 3+ remains available in the positive electrolyte for reduction.
  • Fe 3+ availability may be maintained by increasing a concentration or a volume of the positive electrolyte in the positive electrode compartment 22 side of the redox flow battery cell 18 to provide additional Fe 3+ ions via an external source, such as an external positive electrolyte chamber 52. More commonly, availability of Fe 0 during discharge may be an issue in IFB systems, wherein the Fe 0 available for discharge may be proportional to a surface area and a volume of the negative electrode substrate, as well as to a plating efficiency. Charge capacity may be dependent on the availability of Fe 2+ in the negative electrode compartment 20.
  • Fe 2+ availability may be maintained by providing additional Fe 2+ ions via an external source, such as an external negative electrolyte chamber 50 to increase a concentration or a volume of the negative electrolyte to the negative electrode compartment 20 side of the redox flow battery cell 18.
  • an external source such as an external negative electrolyte chamber 50 to increase a concentration or a volume of the negative electrolyte to the negative electrode compartment 20 side of the redox flow battery cell 18.
  • the positive electrolyte may include ferrous iron, ferric iron, ferric complexes, or any combination thereof
  • the negative electrolyte may include ferrous iron or ferrous complexes, depending on a state of charge (SOC) of the IFB system.
  • SOC state of charge
  • Fe 3+ ions penetrating the separator 24 and crossing over to the negative electrode compartment 20 may result in coulombic efficiency losses.
  • Fe 3+ ions crossing over from the low pH redox side (e.g., more acidic positive electrode compartment 22) to the high pH plating side (e.g., less acidic negative electrode compartment 20) may result in precipitation of Fe(OH) 3 .
  • Precipitation of Fe(OH)3 may degrade the separator 24 and cause permanent battery performance and efficiency losses.
  • Fe(OH)3 precipitate may chemically foul an organic functional group of an ion-exchange membrane or physically clog micropores of the ion-exchange membrane.
  • membrane ohmic resistance may rise over time and battery performance may degrade.
  • Precipitate may be removed by washing the IFB with acid, but constant maintenance and downtime may be disadvantageous for commercial battery applications. Furthermore, washing may be dependent on regular preparation of electrolyte, contributing to additional processing costs and complexity.
  • adding specific organic acids to the positive electrolyte and the negative electrolyte in response to electrolyte pH changes may mitigate precipitate formation during battery charge and discharge cycling without driving up overall costs. Additionally, implementing a membrane barrier that inhibits Fe 3+ ion crossover may also mitigate fouling.
  • IFB electrolyte e.g., FeCl 2 , FeCl 3 , FeSO 4 , Fe 2 (SO 4 ) 3 , and the like
  • the IFB electrolyte may be readily available and may be produced at low costs.
  • the IFB electrolyte may be formed from ferrous chloride (FeCl2), potassium chloride (KCl), manganese(II) chloride (MnCl2), and boric acid (H3BO3).
  • the IFB electrolyte may offer higher reclamation value because the same electrolyte may be used for the negative electrolyte and the positive electrolyte, consequently reducing cross-contamination issues as compared to other systems.
  • iron because of iron’s electron configuration, iron may solidify into a generally uniform solid structure during plating thereof on the negative electrode substrate. For zinc and other metals commonly used in hybrid redox batteries, solid dendritic structures may form during plating.
  • a stable electrode morphology of the IFB system may increase the efficiency of the battery in comparison to other redox flow batteries. Further still, iron redox flow batteries may reduce the use of toxic raw materials and may operate at a relatively neutral pH as compared to other redox flow battery electrolytes.
  • the redox flow battery system 10 may include the redox flow battery cell 18 fluidly coupled to an integrated multi-chambered electrolyte storage tank 110.
  • the redox flow battery cell 18 may include the negative electrode compartment 20, separator 24, and positive electrode compartment 22.
  • the separator 24 may include an electrically insulating ionic conducting barrier which prevents bulk mixing of the positive electrolyte and the negative electrolyte while allowing conductance of specific ions therethrough.
  • the separator 24 may include an ion-exchange membrane and/or a microporous membrane.
  • the negative electrode compartment 20 may include the negative electrode 26, and the negative electrolyte may include electroactive materials.
  • the positive electrode compartment 22 may include the positive electrode 28, and the positive electrolyte may include electroactive materials.
  • multiple redox flow battery cells 18 may be combined in series or in parallel to generate a higher voltage or electric current in the redox flow battery system 10.
  • FIG. 1 Further illustrated in FIG. 1 are negative and positive electrolyte pumps 30 and 32, both used to pump electrolyte solution through the redox flow battery system 10.
  • Electrolytes are stored in one or more tanks external to the cell, and are pumped via the negative and positive electrolyte pumps 30 and 32 through the negative electrode compartment 20 side and the positive electrode compartment 22 side of the redox flow battery cell 18, respectively.
  • the redox flow battery system 10 may also include a first bipolar plate 36 and a second bipolar plate 38, each positioned along a rear-facing side, e.g., opposite of a side facing the separator 24, of the negative electrode 26 and the positive electrode 28, respectively.
  • the first bipolar plate 36 may be in contact with the negative electrode 26 and the second bipolar plate 38 may be in contact with the positive electrode 28.
  • the bipolar plates 36 and 38 may be arranged proximate but spaced away from the electrodes 26 and 28 and housed within the respective electrode compartments 20 and 22. In either case, the bipolar plates 36 and 38 may be electrically coupled to the terminals 40 and 42, respectively, either via direct contact therewith or through the negative and positive electrodes 26 and 28, respectively.
  • the IFB electrolytes may be transported to reaction sites at the negative and positive electrodes 26 and 28 by the first and second bipolar plates 36 and 38, resulting from conductive properties of a material of the bipolar plates 36 and 38. Electrolyte flow may also be assisted by the negative and positive electrolyte pumps 30 and 32, facilitating forced convection through the redox flow battery cell 18.
  • Reacted electrochemical species may also be directed away from the reaction sites by a combination of forced convection and a presence of the first and second bipolar plates 36 and 38.
  • the redox flow battery cell 18 may further include the negative battery terminal 40 and the positive battery terminal 42.
  • the positive electrolyte When a charge current is applied to the battery terminals 40 and 42, the positive electrolyte may be oxidized (loses one or more electrons) at the positive electrode 28, and the negative electrolyte may be reduced (gains one or more electrons) at the negative electrode 26.
  • reverse redox reactions may occur on the electrodes 26 and 28.
  • the positive electrolyte may be reduced (gains one or more electrons) at the positive electrode 28, and the negative electrolyte may be oxidized (loses one or more electrons) at the negative electrode 26.
  • An electrical potential difference across the battery may be maintained by the electrochemical redox reactions in the positive electrode compartment 22 and the negative electrode compartment 20, and may induce an electric current through a current collector while the reactions are sustained.
  • An amount of energy stored by a redox battery may be limited by an amount of electroactive material available in electrolytes for discharge, depending on a total volume of electrolytes and a solubility of the electroactive materials.
  • the redox flow battery system 10 may further include the integrated multi-chambered electrolyte storage tank 110.
  • the multi-chambered electrolyte storage tank 110 may be divided by a bulkhead 98.
  • the bulkhead 98 may create multiple chambers within the multi-chambered electrolyte storage tank 110 so that both the positive and negative electrolytes may be included within a single tank.
  • the negative electrolyte chamber 50 holds negative electrolyte including the electroactive materials
  • the positive electrolyte chamber 52 holds positive electrolyte including the electroactive materials.
  • the bulkhead 98 may be positioned within the multi-chambered electrolyte storage tank 110 to yield a desired volume ratio between the negative electrolyte chamber 50 and the positive electrolyte chamber 52.
  • the bulkhead 98 may be positioned to set a volume ratio of the negative and positive electrolyte chambers 50 and 52 according to a stoichiometric ratio between the negative and positive redox reactions.
  • FIG. 1 further illustrates a fill height 112 of the multi-chambered electrolyte storage tank 110, which may indicate a liquid level in each tank compartment.
  • FIG.1 also shows a gas head space 90 located above the fill height 112 of the negative electrolyte chamber 50, and a gas head space 92 located above the fill height 112 of the positive electrolyte chamber 52.
  • the gas head space 92 may be utilized to store H 2 gas generated through operation of the redox flow battery (e.g., due to proton reduction and iron corrosion side reactions) and conveyed to the multi-chambered electrolyte storage tank 110 with returning electrolyte from the redox flow battery cell 18.
  • the H2 gas may be separated spontaneously at a gas-liquid interface (e.g., the fill height 112) within the multi- chambered electrolyte storage tank 110, thereby precluding having additional gas-liquid separators as part of the redox flow battery system 10. Once separated from the electrolyte, the H2 gas may fill the gas head spaces 90 and 92.
  • the stored H 2 gas may aid in purging other gases from the multi-chambered electrolyte storage tank 110, thereby acting as an inert gas blanket for reducing oxidation of electrolyte species, which may help to reduce redox flow battery capacity losses.
  • utilizing the integrated multi-chambered electrolyte storage tank 110 may forego having separate negative and positive electrolyte storage tanks, hydrogen storage tanks, and gas-liquid separators common to conventional redox flow battery systems, thereby simplifying a system design, reducing a physical footprint of the redox flow battery system 10, and reducing system costs.
  • FIG.1 also shows a spillover hole 96, which may create an opening in the bulkhead 98 between the gas head spaces 90 and 92, and may provide a means of equalizing gas pressure between the chambers 50 and 52.
  • the spillover hole 96 may be positioned at a threshold height above the fill height 112.
  • the spillover hole 96 may further enable a capability to self-balance the electrolytes in each of the negative and positive electrolyte chambers 50 and 52 in the event of a battery crossover.
  • the same electrolyte (Fe 2+ ) is used in both negative and positive electrode compartments 20 and 22, so spilling over of electrolyte between the negative and positive electrolyte chambers 50 and 52 may reduce overall system efficiency, but overall electrolyte composition, battery module performance, and battery module capacity may be maintained.
  • Flange fittings may be utilized for all piping connections for inlets and outlets to and from the multi-chambered electrolyte storage tank 110 to maintain a continuously pressurized state without leaks.
  • the multi-chambered electrolyte storage tank 110 may include at least one outlet from each of the negative and positive electrolyte chambers 50 and 52, and at least one inlet to each of the negative and positive electrolyte chambers 50 and 52. Furthermore, one or more outlet connections may be provided from the gas head spaces 90 and 92 for directing H2 gas to rebalancing reactors or cells 80 and 82, such that the rebalancing reactors or cells 80 and 82 may be respectively fluidically coupled to the gas head spaces 90 and 92. [0042] Although not shown in FIG.1, the integrated multi-chambered electrolyte storage tank 110 may further include one or more heaters thermally coupled to each of the negative electrolyte chamber 50 and the positive electrolyte chamber 52.
  • only one of the negative and positive electrolyte chambers 50 and 52 may include one or more heaters.
  • the negative electrolyte may be heated by transferring heat generated at the redox flow battery cell 18 to the negative electrolyte. In this way, the redox flow battery cell 18 may heat and facilitate temperature regulation of the negative electrolyte.
  • the one or more heaters may be actuated by a controller 88 to regulate a temperature of the negative electrolyte chamber 50 and the positive electrolyte chamber 52 independently or together.
  • the controller 88 may increase a power supplied to one or more heaters so that a heat flux to the electrolyte may be increased.
  • the electrolyte temperature may be indicated by one or more temperature sensors mounted at the multi-chambered electrolyte storage tank 110, such as sensors 60 and 62.
  • the one or more heaters may include coil type heaters or other immersion heaters immersed in the electrolyte fluid, or surface mantle type heaters that transfer heat conductively through the walls of the negative and positive electrolyte chambers 50 and 52 to heat the fluid therein. Other known types of tank heaters may be employed without departing from the scope of the present disclosure.
  • the controller 88 may deactivate the one or more heaters in the negative and positive electrolyte chambers 50 and 52 in response to a liquid level decreasing below a solids fill threshold level. Said in another way, in some examples, the controller 88 may activate the one or more heaters in the negative and positive electrolyte chambers 50 and 52 only in response to a liquid level increasing above the solids fill threshold level. In this way, activating the one or more heaters without sufficient liquid in the negative and/or positive electrolyte chambers 50, 52 may be averted, thereby reducing a risk of overheating or burning out the heater(s).
  • one or more inlet connections may be provided to each of the negative and positive electrolyte chambers 50 and 52 from a field hydration system (not shown).
  • the field hydration system may facilitate commissioning of the redox flow battery system 10, including installing, filling, and hydrating the redox flow battery system 10, at an end-use location.
  • the redox flow battery system 10 may be dry-assembled at a battery manufacturing facility different from the end-use location without filling and hydrating the redox flow battery system 10, before delivering the redox flow battery system 10 to the end-use location.
  • the end-use location may correspond to a location where the redox flow battery system 10 is to be installed and utilized for on-site energy storage.
  • the redox flow battery system 10 may be designed such that, once installed and hydrated at the end-use location, a position of the redox flow battery system 10 may become fixed, and the redox flow battery system 10 may no longer be deemed a portable, dry system.
  • the dry, portable redox flow battery system 10 may be delivered on-site, after which the redox flow battery system 10 may be installed, hydrated, and commissioned.
  • the redox flow battery system 10 Prior to hydration, the redox flow battery system 10 may be referred to as a dry, portable system, the redox flow battery system 10 being free of or without water and wet electrolyte. Once hydrated, the redox flow battery system 10 may be referred to as a wet, non-portable system, the redox flow battery system 10 including wet electrolyte. [0044] Further illustrated in FIG. 1, electrolyte solutions primarily stored in the multi- chambered electrolyte storage tank 110 may be pumped via the negative and positive electrolyte pumps 30 and 32 throughout the redox flow battery system 10.
  • Electrolyte stored in the negative electrolyte chamber 50 may be pumped via the negative electrolyte pump 30 through the negative electrode compartment 20 side of the redox flow battery cell 18, and electrolyte stored in the positive electrolyte chamber 52 may be pumped via the positive electrolyte pump 32 through the positive electrode compartment 22 side of the redox flow battery cell 18.
  • the electrolyte rebalancing reactors 80 and 82 may be connected in line or in parallel with the recirculating flow paths of the electrolyte at the negative and positive sides of the redox flow battery cell 18, respectively, in the redox flow battery system 10.
  • One or more rebalancing reactors may be connected in-line with the recirculating flow paths of the electrolyte at the negative and positive sides of the battery, and other rebalancing reactors may be connected in parallel, for redundancy (e.g., a rebalancing reactor may be serviced without disrupting battery and rebalancing operations) and for increased rebalancing capacity.
  • the electrolyte rebalancing reactors 80 and 82 may be placed in a return flow path from the negative and positive electrode compartments 20 and 22 to the negative and positive electrolyte chambers 50 and 52, respectively.
  • the electrolyte rebalancing reactors 80 and 82 may serve to rebalance electrolyte charge imbalances in the redox flow battery system 10 occurring due to side reactions, ion crossover, and the like, as described herein.
  • one or both of the rebalancing reactors 80 and 82 may include trickle bed reactors, where the H2 gas and the (liquid) electrolyte may be contacted at catalyst surfaces in a packed bed for carrying out the electrolyte rebalancing reaction.
  • one or both of the rebalancing reactors 80 and 82 may have catalyst beds configured in a jelly roll.
  • one or both of the rebalancing reactors 80 and 82 may include flow-through type reactors that are capable of contacting the H2 gas and the electrolyte and carrying out the electrolyte rebalancing reactions absent a packed catalyst bed.
  • flow-through type reactors that are capable of contacting the H2 gas and the electrolyte and carrying out the electrolyte rebalancing reactions absent a packed catalyst bed.
  • lower Fe 3+ reduction rates e.g., on the order of ⁇ 1-3 mol/m 2 hr
  • electrolyte rebalancing may preclude implementation of such rebalancing reactor configurations in higher performance applications.
  • one or both of the rebalancing reactors 80 and 82 may include fuel cells, where the H 2 gas and the electrolyte may be contacted at catalyst surfaces for carrying out the electrolyte rebalancing reaction and where a closed circuit may be formed by directing electric current from the fuel cells through an external load.
  • reverse current spikes e.g., transient increases in reverse electric current, where “reverse electric current” may be used herein to refer to any electric current traveling along an electrical pathway in a direction opposite from expected (that is, opposite from a “forward” direction)] in such fuel cells may be unavoidable in certain circumstances, undermining a reliability of such rebalancing reaction configurations.
  • a rebalancing cell such as the rebalancing cell of FIGS.2A and 2B, including a stack of internally shorted electrode assemblies, such as the electrode assembly of FIG. 3, configured to drive the H 2 gas and the electrolyte to react at catalyst surfaces via a combination of internal electric current, convection, gravity feeding, and capillary action.
  • the electrode assemblies of the stack of internally shorted electrode assemblies may be referred to as “internally shorted,” in that no electric current may be directed away from the stack of internally shorted electrode assemblies during operation of the rebalancing cell.
  • each electrode assembly of the stack of internally shorted electrode assemblies may be electrically decoupled from each other electrode assembly of the stack of internally shorted electrode assemblies, such that degradation to the stack of internally shorted electrode assemblies during current spikes at one electrode assembly may be limited thereto (e.g., reverse electric current may not be driven from one electrode assembly through the other electrode assemblies).
  • each electrode assembly of the stack of internally shorted electrode assemblies may include an interfacing pair of positive and negative electrodes (e.g., configured in face-sharing contact with one another so as to be continuously electrically conductive).
  • first and second components may be described as “interfacing” with one another when the first component is arranged adjacent to the second component such that the first and second components are in face-sharing contact with one another (where “adjacent” is used herein to refer to any two components having no intervening components therebetween).
  • adjacent is used herein to refer to any two components having no intervening components therebetween.
  • continuous when describing electrical conductivity of multiple electrodes may refer to an electrical pathway therethrough having effectively or practically zero resistance at any face- sharing interfaces of the multiple electrodes.
  • the (positive) rebalancing reactor 82 may be the rebalancing cell including the stack of internally shorted electrode assemblies.
  • the (negative) rebalancing reactor 80 may be of like configuration [Fe 3+ may be generated at the negative electrode 26 during iron plating oxidation (see equation (3))]. [0051] During operation of the redox flow battery system 10, sensors and probes may monitor and control chemical properties of the electrolyte such as electrolyte pH, concentration, SOC, and the like.
  • sensors 62 and 60 may be positioned to monitor positive electrolyte and negative electrolyte conditions at the positive electrolyte chamber 52 and the negative electrolyte chamber 50, respectively.
  • sensors 62 and 60 may each include one or more electrolyte level sensors to indicate a level of electrolyte in the positive electrolyte chamber 52 and the negative electrolyte chamber 50, respectively.
  • sensors 72 and 70 also illustrated in FIG. 1, may monitor positive electrolyte and negative electrolyte conditions at the positive electrode compartment 22 and the negative electrode compartment 20, respectively.
  • the sensors 72 and 70 may be pH probes, optical probes, pressure sensors, voltage sensors, etc.
  • sensors may be positioned at other locations throughout the redox flow battery system 10 to monitor electrolyte chemical properties and other properties.
  • a sensor may be positioned in an external acid tank (not shown) to monitor acid volume or pH of the external acid tank, wherein acid from the external acid tank may be supplied via an external pump (not shown) to the redox flow battery system 10 in order to reduce precipitate formation in the electrolytes.
  • Additional external tanks and sensors may be installed for supplying other additives to the redox flow battery system 10.
  • various sensors including, temperature, conductivity, and level sensors of a field hydration system may transmit signals to the controller 88.
  • the controller 88 may send signals to actuators such as valves and pumps of the field hydration system during hydration of the redox flow battery system 10. Sensor information may be transmitted to the controller 88 which may in turn actuate the pumps 30 and 32 to control electrolyte flow through the redox flow battery cell 18, or to perform other control functions, as an example. In this manner, the controller 88 may be responsive to one or a combination of sensors and probes.
  • the redox flow battery system 10 may further include a source of H 2 gas.
  • the source of H2 gas may include a separate dedicated hydrogen gas storage tank.
  • H2 gas may be stored in and supplied from the integrated multi-chambered electrolyte storage tank 110.
  • the integrated multi-chambered electrolyte storage tank 110 may supply additional H 2 gas to the positive electrolyte chamber 52 and the negative electrolyte chamber 50.
  • the integrated multi-chambered electrolyte storage tank 110 may alternately supply additional H 2 gas to an inlet of the electrolyte rebalancing reactors 80 and 82.
  • a mass flow meter or other flow controlling device (which may be controlled by the controller 88) may regulate flow of the H2 gas from the integrated multi-chambered electrolyte storage tank 110.
  • the integrated multi-chambered electrolyte storage tank 110 may supplement the H2 gas generated in the redox flow battery system 10.
  • the H2 gas may be supplied from the integrated multi-chambered electrolyte storage tank 110 in order to rebalance the SOC of the electroactive materials in the positive electrolyte and the negative electrolyte.
  • the controller 88 may supply the H2 gas from the integrated multi-chambered electrolyte storage tank 110 in response to a measured change in pH or in response to a measured change in SOC of an electrolyte or an electroactive material.
  • an increase in pH of the negative electrolyte chamber 50, or the negative electrode compartment 20 may indicate that H2 gas is leaking from the redox flow battery system 10 and/or that the reaction rate is too slow with the available hydrogen partial pressure, and the controller 88, in response to the pH increase, may increase a supply of H2 gas from the integrated multi-chambered electrolyte storage tank 110 to the redox flow battery system 10.
  • the controller 88 may supply H2 gas from the integrated multi-chambered electrolyte storage tank 110 in response to a pH change, wherein the pH increases beyond a first threshold pH or decreases beyond a second threshold pH.
  • the controller 88 may supply additional H2 gas to increase a rate of reduction of Fe 3+ ions and a rate of production of protons, thereby reducing the pH of the positive electrolyte.
  • the pH of the negative electrolyte may be lowered by hydrogen reduction of Fe 3+ ions crossing over from the positive electrolyte to the negative electrolyte or by protons, generated at the positive side, crossing over to the negative electrolyte due to a proton concentration gradient and electrophoretic forces. In this manner, the pH of the negative electrolyte may be maintained within a stable region, while reducing the risk of precipitation of Fe 3+ ions (crossing over from the positive electrode compartment 22) as Fe(OH)3.
  • control schemes for controlling a supply rate of H 2 gas from the integrated multi- chambered electrolyte storage tank 110 responsive to a change in an electrolyte pH or to a change in an electrolyte SOC, detected by other sensors such as an oxygen-reduction potential (ORP) meter or an optical sensor, may be implemented.
  • the change in pH or SOC triggering action of the controller 88 may be based on a rate of change or a change measured over a time period. The time period for the rate of change may be predetermined or adjusted based on time constants for the redox flow battery system 10.
  • the time period may be reduced if a recirculation rate is high, and local changes in concentration (e.g., due to side reactions or gas leaks) may quickly be measured since the time constants may be small.
  • the controller 88 may further execute control schemes based on an operating mode of the redox flow battery system 10. For example, and as discussed in detail below with reference to FIG.
  • the controller 88 may control flows of the negative and positive electrolytes to the rebalancing reactors 80 and 82, respectively, during charging and discharging of the redox flow battery cell 18 so as to simultaneously rid the redox flow battery system 10 of excess H 2 gas and reduce Fe 3+ ion concentration.
  • the controller 88 may direct flow of any excess or unreacted H2 along with the rebalanced negative and positive electrolytes (e.g., including a decreased concentration of Fe 3+ and an increased concentration of Fe 2+ ) from the rebalancing reactors 80 and 82 back into the respective electrolyte chambers 50 and 52 of the multi-chambered electrolyte storage tank 110. Additionally or alternatively, the unreacted H2 gas may be returned to the separate dedicated hydrogen gas storage tank (not shown at FIG.1).
  • the rebalanced negative and positive electrolytes e.g., including a decreased concentration of Fe 3+ and an increased concentration of Fe 2+
  • the controller 88 may further control charging and discharging of the redox flow battery cell 18 so as to cause iron preformation at the negative electrode 26 during system conditioning (where system conditioning may include an operating mode employed to optimize electrochemical performance of the redox flow battery system 10 outside of battery cycling). That is, during system conditioning, the controller 88 may adjust one or more operating conditions of the redox flow battery system 10 to plate iron metal on the negative electrode 26 to improve a battery charge capacity during subsequent battery cycling (thus, the iron metal may be preformed for battery cycling). In this way, preforming iron at the negative electrode 26 and running electrolyte rebalancing during the system conditioning may increase an overall capacity of the redox flow battery cell 18 during battery cycling by mitigating iron plating loss.
  • system conditioning may include an operating mode employed to optimize electrochemical performance of the redox flow battery system 10 outside of battery cycling. That is, during system conditioning, the controller 88 may adjust one or more operating conditions of the redox flow battery system 10 to plate iron metal on the negative electrode 26 to improve a battery charge capacity during subsequent battery
  • battery cycling may include alternating between a charging mode and a discharging mode of the redox flow battery system 10.
  • charge cycling also referred to as “charge cycling”
  • all components apart from the sensors 60 and 62 and the integrated multi-chambered electrolyte storage tank 110 (and components included therein) may be considered as being included in a power module 120.
  • the redox flow battery system 10 may be described as including the power module 120 fluidly coupled to the integrated multi- chambered electrolyte storage tank 110 and communicably coupled to the sensors 60 and 62.
  • each of the power module 120 and the multi-chambered electrolyte storage tank 110 may be included in a single housing or packaging (not shown), such that the redox flow battery system 10 may be contained as a single unit in a single location.
  • the positive electrolyte, the negative electrolyte, the sensors 60 and 62, the electrolyte rebalancing reactors 80 and 82, and the integrated multi-chambered electrolyte storage tank 110 (and components included therein) may be considered as being included in an electrolyte subsystem 130.
  • the electrolyte subsystem 130 may supply one or more electrolytes to the redox flow battery cell 18 (and components included therein).
  • the rebalancing cell 202 may include a stack of internally shorted electrode assemblies, such as the electrode assembly described in detail below with reference to FIG. 3, which may drive an electrolyte rebalancing reaction by promoting contact between H 2 gas and an electrolyte from positive or negative electrode compartments of a redox flow battery, such as the redox flow battery cell 18 of FIG. 1, at catalytic surfaces of negative electrodes of the stack of internally shorted electrode assemblies.
  • the rebalancing cell 202 may be one or both of the rebalancing reactors 80 and 82 of FIG. 1.
  • a set of reference axes 201 is provided for describing relative positioning of the components shown and for comparison between the views of FIGS.2A-4B, 6A, 6B, 9A, and 9B, the axes 201 indicating an x-axis, a y-axis, and a z-axis.
  • an additional axis g may be parallel with a direction of gravity (e.g., in a positive direction along the axis g) and a vertical direction (e.g., in a negative direction along the axis g and opposite to the direction of gravity).
  • a direction of gravity e.g., in a positive direction along the axis g
  • a vertical direction e.g., in a negative direction along the axis g and opposite to the direction of gravity.
  • a 75 kW redox flow battery system may include two rebalancing cells 202 including a stack of 20 electrode assemblies (e.g., a stack of 19 bipolar assemblies with 2 end plates positioned at opposite ends of the stack).
  • the stack of internally shorted electrode assemblies may be removably enclosed within an external cell enclosure (e.g., housing) 204.
  • the cell enclosure 204 may include a top cover removably affixed to an enclosure base, such that the top cover may be temporarily removed to replace or diagnose one or more electrode assemblies of the stack of internally shorted electrode assemblies.
  • the cell enclosure 204 depicted in FIGS.
  • the cell enclosure 204 may be composed of a material having a low electrical conductivity, such as a plastic or other polymer, so as to reduce undesirable shorting events.
  • the cell enclosure 204 may further be configured to include openings or cavities for interfacial components of the rebalancing cell 202.
  • the cell enclosure 204 may include a plurality of inlet and outlet ports configured to fluidically couple to other components of the redox flow battery system.
  • the plurality of inlet and outlet ports may include polypropylene (PP) flange fittings fusion welded to PP plumbing.
  • the plurality of inlet and outlet ports may include an electrolyte inlet port 206 for flowing the electrolyte into the cell enclosure 204 and an electrolyte outlet port 208 for expelling the electrolyte from the cell enclosure 204.
  • the electrolyte inlet port 206 may be positioned on an upper half of the cell enclosure 204 and the electrolyte outlet port 208 may be positioned on a lower half of the cell enclosure 204 (where the upper half and the lower half of the cell enclosure 204 are separated along the z-axis by a plane parallel with each of the x- and y-axes). Accordingly, the electrolyte outlet port 208 may be positioned lower than the electrolyte inlet port 206 with respect to the direction of gravity (e.g., along the axis g).
  • the electrolyte may be distributed across the stack of internally shorted electrode assemblies, gravity fed through the stack of electrode assemblies, wicked up (e.g., against the direction of gravity) through positive electrodes of the stack of internally shorted electrode assemblies to react at the catalytic surfaces of the negative electrodes in a cathodic half reaction, and expelled out of the cell enclosure 204 via the electrolyte outlet port 208.
  • the rebalancing cell 202 may further be tilted or inclined with respect to the direction of gravity via a sloped support 220 coupled to the cell enclosure 204.
  • tilting of the cell enclosure 204 in this way may further assist in electrolyte draining of the rebalancing cell 202 (e.g., during an idle mode of the redox flow battery system) and keep the catalytic surfaces relatively dry (as the catalytic surfaces may corrode after being soaked in the electrolyte for a sufficient duration, in some examples).
  • the sloped support 220 may tilt the cell enclosure 204 at an angle 222 such that planes of electrode sheets of the stack of internally shorted electrode assemblies are inclined with respect to a lower surface (not shown) on which the sloped support 220 rests at the angle 222.
  • the angle 222 (e.g., of the cell enclosure 204 with respect to the lower surface) may be between 0° and 30°. In embodiments wherein the angle 222 is substantially 0°, the rebalancing cell 202 may still function, though tilting the cell enclosure 204 by an angle greater than 0° may allow the pressure drop to be greater for electrolyte crossover to the negative electrodes to be reduced. In some examples, the angle 222 may be between 2° and 30°. In some examples, the angle 222 may be between 2° and 20°. In one example, the angle 222 may be about 8°.
  • the pressure drop of the electrolyte upon entering the cell enclosure 204 may be increased by increasing the angle 222 and decreased by decreasing the angle 222. Further aspects of the sloped support 220 are described in greater detail below with reference to FIGS.9A and 9B.
  • one or more support rails 224 may be coupled to the upper half of the cell enclosure 204 (e.g., opposite from the sloped support 220).
  • the one or more support rails 224 may be tilted with respect to the cell enclosure 204 at the angle 222 such that the one or more support rails 224 may removably fasten the rebalancing cell 202 to an upper surface above and parallel with the lower surface.
  • the z-axis may likewise be offset from the axis g at the angle 222 (e.g., the cell enclosure 204 may be tilted with respect to a vertical direction opposite the direction of gravity by the angle 222, as shown in FIGS. 2A and 2B).
  • gravity feeding of the electrolyte through the rebalancing cell 202 may further be assisted by positioning the rebalancing cell 202 above an electrolyte storage tank (e.g., the multi-chambered electrolyte storage tank 110 of FIG.1) of the redox flow battery system with respect to the vertical direction opposite to the direction of gravity. Further aspects of the electrolyte flow will be discussed in greater detail below with reference to FIGS.6A-7B.
  • the electrolyte outlet port 208 may include a plurality of openings in the cell enclosure 204 configured to expel at least a portion of the electrolyte (each of the plurality of openings including the PP flange fitting fusion welded to PP plumbing).
  • the electrolyte outlet port 208 is shown including five openings.
  • the electrolyte may be evenly distributed across the stack of internally shorted electrode assemblies and may be expelled from the cell enclosure 204 with substantially unimpeded flow (“substantially” may be used herein as a qualifier meaning “effectively”).
  • the electrolyte outlet port 208 may include more than five openings or less than five openings.
  • the electrolyte outlet port 208 may include a single opening.
  • the electrolyte outlet port 208 may be positioned beneath the cell enclosure 204 with respect to the z-axis (e.g., on a face of the cell enclosure 204 facing a negative direction of the z- axis).
  • the electrolyte inlet port 206 and the electrolyte outlet port 208 may be positioned on the cell enclosure 204 based on a flow path of the electrolyte through the stack of internally shorted electrode assemblies (e.g., from the electrolyte inlet port 206 to the electrolyte outlet port 208 and inclusive of channels, passages, plenums, wells, etc.
  • the electrolyte inlet port 206 and the electrolyte outlet port 208 may be positioned on adjacent sides of the cell enclosure 204 (e.g., faces of the cell enclosure 204 sharing a common edge). In other examples, the electrolyte inlet port 206 and the electrolyte outlet port 208 may be positioned on opposite sides of the cell enclosure 204. In other examples, the electrolyte inlet port 206 and the electrolyte outlet port 208 may be positioned on the same side of the cell enclosure 204.
  • the electrolyte inlet port 206 may be positioned on a face of the cell enclosure 204 facing a negative direction of the x-axis. In additional or alternative examples, the electrolyte inlet port 206 may be positioned on a face of the cell enclosure 204 facing a positive direction of the x-axis. In one example, and as shown, one opening of the electrolyte inlet port 206 may be positioned on the face of the cell enclosure 204 facing the negative direction of the x- axis and another opening of the electrolyte inlet port 206 may be positioned on the face of the cell enclosure 204 facing the positive direction of the x-axis.
  • the plurality of inlet and outlet ports may further include a hydrogen gas inlet port 210 for flowing the H2 gas into the cell enclosure 204 and a hydrogen gas outlet port 212 (as shown in FIG.2B) for expelling the H2 gas from the cell enclosure 204.
  • each of the hydrogen gas inlet port 210 and the hydrogen gas outlet port 212 may be positioned on the lower half of the cell enclosure 204 (e.g., at a lowermost electrode assembly of the stack of internally shorted electrode assemblies along the z-axis).
  • each of the hydrogen gas inlet port 210 and the hydrogen gas outlet port 212 may be positioned on the upper half of the cell enclosure 204 (e.g., at an uppermost electrode assembly of the stack of internally shorted electrode assemblies along the z-axis).
  • the hydrogen gas inlet port 210 may be positioned on the lower half of the cell enclosure 204 and the hydrogen gas outlet port 212 may be positioned on the upper half of the cell enclosure 204.
  • the hydrogen gas inlet port 210 may be positioned lower than the hydrogen gas outlet port 212 with respect to the direction of gravity (e.g., along the axis g).
  • the H 2 gas may be distributed across and through the stack of internally shorted electrode assemblies via forced convection (e.g., induced by flow field configurations of respective flow field plates, as discussed in greater detail below with reference to FIGS.5A-5D and 8A-8D) and decomposed at the catalytic surfaces of the negative electrodes in an anodic half reaction.
  • forced convection e.g., induced by flow field configurations of respective flow field plates, as discussed in greater detail below with reference to FIGS.5A-5D and 8A-8D
  • excess, unreacted H 2 gas may remain in the rebalancing cell 202 following contact with the catalytic surfaces.
  • at least a portion of the H2 gas which has not reacted at the catalytic surfaces may pass into the electrolyte.
  • the plurality of inlet and outlet ports may further include a pressure release outlet port 214 (as shown in FIG. 2A) to expel unreacted H 2 gas from the electrolyte.
  • the hydrogen gas outlet port 212 may be configured to expel at least a portion of the H 2 gas which has not reacted at the catalytic surfaces and that has not flowed through the negative electrodes into the electrolyte. Further aspects of the H 2 gas flow will be discussed in greater detail below with reference to FIGS. 4A-5D.
  • the hydrogen gas inlet port 210 and the hydrogen gas outlet port 212 may be positioned on the cell enclosure 204 based on a flow path of the H2 gas through the stack of internally shorted electrode assemblies.
  • the flow path may be from the hydrogen gas inlet port 210 to the hydrogen gas outlet port 212 (when included) and inclusive of channels, passages, plenums, etc., within the cell enclosure 204 and fluidically coupled to the hydrogen gas inlet port 210 and the hydrogen gas outlet port 212 (when included).
  • the hydrogen gas inlet port 210 and the hydrogen gas outlet port 212 may be positioned on opposite sides of the cell enclosure 204.
  • the hydrogen gas inlet port 210 and the hydrogen gas outlet port 212 may be positioned on adjacent sides of the cell enclosure 204. In other examples, the hydrogen gas inlet port 210 and the hydrogen gas outlet port 212 may be positioned on the same side of the cell enclosure 204.
  • the hydrogen gas inlet port 210 is shown in FIGS.2A and 2B as being positioned on the face of the cell enclosure 204 facing the negative direction of the x-axis and the hydrogen gas outlet port 212 is shown in FIGS.2A and 2B as being positioned on the face of the cell enclosure 204 facing the positive direction of the x- axis
  • the hydrogen gas inlet port 210 may be positioned on the face of the cell enclosure 204 facing the positive direction of the x-axis
  • the hydrogen gas outlet port 212 may be positioned on the face of the cell enclosure 204 facing the negative direction of the x-axis.
  • the hydrogen gas inlet port 210, the hydrogen gas outlet port 212, the electrolyte inlet port 206, and the electrolyte outlet port 208 may be positioned on the cell enclosure 204 in a crosswise configuration.
  • the crosswise configuration may include the hydrogen gas outlet port 212 and the electrolyte inlet port 206 being positioned on different sides (e.g., faces) of the upper half of the cell enclosure 204 and the hydrogen gas inlet port 210 and the electrolyte outlet port 208 being positioned on different sides of the lower half of the cell enclosure 204.
  • no hydrogen gas outlet port 212 may be present for expelling H 2 gas which has not reacted at the catalytic surfaces of the negative electrodes and which has not flowed through the negative electrodes into the electrolyte.
  • the pressure release outlet port 214 for expelling unreacted H 2 gas from the electrolyte may still be present, and the unreacted H 2 gas may only be expelled from the cell enclosure 204 after flowing through the negative electrodes into the electrolyte and through the pressure release outlet port 214.
  • Exemplary rebalancing cell configurations lacking the hydrogen gas outlet port 212, whether or not including the pressure release outlet port 214, may be referred to as “dead ended configurations.”
  • dead ended configurations substantially all of the H2 gas may be forced into contact with the catalytic surfaces of the negative electrodes, whereat the H2 gas may either decompose via the anodic half reaction and/or the H 2 gas may enter the electrolyte after passing through the negative electrodes (e.g., without reacting at catalytic surfaces thereof).
  • FIG.3 an exploded view 300 depicting an electrode assembly 302 for a rebalancing cell, such as the rebalancing cell 202 of FIGS.2A and 2B, is shown.
  • the electrode assembly 302 may be internally shorted (e.g., electric current flowing through the electrode assembly 302 is not channeled through an external load).
  • the electrode assembly 302 may be included in a stack of electrode assemblies of like configuration in a cell enclosure so as to form the rebalancing cell.
  • the electrode assembly 302 may include a plate 304 with an activated carbon foam 306, a positive electrode 308 (also referred to herein as a “cathode” in certain examples), and a negative electrode 310 (also referred to herein as an “anode” in certain examples) sequentially stacked thereon.
  • the electrode assembly 302 may be positioned within the rebalancing cell so as to receive an electrolyte through the carbon foam 306, wherefrom the electrolyte may enter pores of the positive electrode 308 via capillary action and come into contact with the negative electrode 310.
  • the electrode assembly 302 may further be positioned within the rebalancing cell so as to receive H 2 gas across a catalytic surface of the negative electrode 310 opposite to the positive electrode 308 via convection.
  • the convection of the H 2 gas across the catalytic surface may be assisted by a flow field plate (not shown at FIG.3) interfacing with the catalytic surface.
  • the electrode assembly 302 may be configured for electrolyte rebalancing for a redox flow battery, such as the redox flow battery cell 18 of FIG. 1, fluidically coupled to the rebalancing cell including the electrode assembly 302.
  • the plate 304 may be composed of a material having a low electrical conductivity, such as a plastic or other polymer, so as to reduce undesirable shorting events.
  • the plate 304 may be formed from the same material as the cell enclosure 204 of FIGS.2A and 2B.
  • the plate 304 may include a plurality of inlets and outlets therethrough.
  • the plurality of inlets and outlets may include an electrolyte outlet channel section 316, a hydrogen gas inlet channel section 318a, and a hydrogen gas outlet channel section 318b.
  • the plate 304 may include the electrolyte outlet channel section 316 for directing the electrolyte out of the rebalancing cell, the hydrogen gas inlet channel section 318a for directing the H2 gas into the rebalancing cell and across the negative electrode 310, and the hydrogen gas outlet channel section 318b for directing the H2 gas out of the rebalancing cell.
  • the plate 304 may further include an electrolyte inlet well 312 for receiving the electrolyte at the electrode assembly 302, the electrolyte inlet well 312 fluidically coupled to a plurality of electrolyte inlet passages 314a set into a berm 314b positioned adjacent to the carbon foam 306 for distributing the received electrolyte across the carbon foam 306.
  • the electrolyte inlet well 312 may receive the electrolyte from an electrolyte inlet port (e.g., the electrolyte inlet port 206 of FIGS. 2A and 2B) fluidically coupled thereto (e.g., via an electrolyte inlet channel; not shown at FIG.3), the electrolyte outlet channel section 316 may expel the electrolyte through an electrolyte outlet port (e.g., the electrolyte outlet port 208 of FIGS. 2A and 2B) fluidically coupled thereto, the hydrogen gas inlet channel section 318a may receive the H2 gas from a hydrogen gas inlet port (e.g., the hydrogen gas inlet port 210 of FIGS.
  • an electrolyte inlet port e.g., the electrolyte inlet port 206 of FIGS. 2A and 2B
  • the electrolyte outlet channel section 316 may expel the electrolyte through an electrolyte outlet port (e.g., the electrolyte outlet
  • the hydrogen gas outlet channel section 318b may expel the H2 gas through a hydrogen gas outlet port (e.g., the hydrogen gas outlet port 212 of FIGS.2A and 2B) fluidically coupled thereto.
  • a hydrogen gas outlet port e.g., the hydrogen gas outlet port 212 of FIGS.2A and 2B
  • the hydrogen gas inlet channel section 318a is described herein as a section of a hydrogen gas inlet channel and the hydrogen gas outlet channel section 318b is described herein as a section of a hydrogen gas outlet channel
  • the channel section 318b may be a section of a hydrogen gas inlet channel (e.g., for directing the H2 gas into the rebalancing cell and across the negative electrode 310 after receiving the H2 gas from the hydrogen gas inlet port) and the gas inlet channel section 318a may be a section of a hydrogen gas outlet channel (e.g., for directing the H 2 gas out of the rebalancing cell by expelling the H2 gas through the hydrogen gas outlet port).
  • the rebalancing cell may be configured as a dead ended configuration and no hydrogen gas outlet port may be fluidically coupled to the hydrogen gas outlet channel section 318b.
  • the hydrogen gas outlet channel section 318b may direct the H 2 gas back across the negative electrode 310 or the hydrogen gas outlet channel section 318b may instead be configured as another hydrogen gas inlet channel section (e.g., for directing a portion of the H 2 gas into the rebalancing cell and across the negative electrode 310 after receiving the portion of the H 2 gas from the hydrogen gas inlet port).
  • the plurality of inlets and outlets may be configured to ease electrolyte and H2 gas flow throughout the rebalancing cell.
  • a size of each of the hydrogen gas inlet channel section 318a and the hydrogen gas outlet channel section 318b may be selected to minimize a pressure drop therethrough, thereby aiding in flow distribution into each electrode assembly 302 of the stack of internally shorted electrode assemblies.
  • a size of each electrolyte inlet passage 314a and a total number of the plurality of electrolyte inlet passages 314a relative to the berm 314b may be selected to induce a relatively small pressure drop to substantially evenly distribute electrolyte flow.
  • the selection of the size of each electrolyte inlet passage 314a and the total number of the plurality of electrolyte inlet passages 314a may be dependent on a number of factors specific to a given configuration of the rebalancing cell, such as a size of an electrolyte flow field and a desired electrolyte flow rate.
  • the electrolyte outlet channel section 316 may further be configured for distributing the electrolyte through multiple openings included in the electrolyte outlet port. For instance, in the exploded view 300 of FIG. 3, the electrolyte outlet channel section 316 is shown including two openings.
  • a number of openings included in the electrolyte outlet channel section 316 may be equal to a number of openings included in the electrolyte outlet port, such that the openings of the electrolyte outlet channel section 316 may respectively correspond to the openings of the electrolyte outlet port. In this way, the electrolyte may be evenly distributed across the electrode assembly 302 and may be expelled from the rebalancing cell with substantially unimpeded flow.
  • the electrolyte outlet channel section 316 may include more than two openings or less than two openings (e.g., a single opening).
  • electrolyte outlet channel sections 316, hydrogen gas inlet channel sections 318a, and hydrogen gas outlet channel sections 318b may align to form a continuous electrolyte outlet channel, a continuous hydrogen gas inlet channel, and a continuous hydrogen gas outlet channel, respectively (as variously shown in FIGS.4A, 4B, 6A, and 6B, described below).
  • the stack of electrode assemblies may be formed in a modular fashion, whereby any practical number of electrode assemblies 302 may be stacked and included in a rebalancing cell.
  • a plurality of sealing inserts may be affixed (as used herein, “affix,” “affixed,” or “affixing” includes, but is not limited to, gluing, attaching, connecting, fastening, joining, linking, or securing one component to another component through a direct or indirect relationship) or otherwise coupled to the plate 304.
  • the plurality of sealing inserts may include a hydrogen gas inlet channel seal insert 320a and a hydrogen gas outlet channel seal insert 320b for inducing flow of the H2 gas across the negative electrode 310 by mitigating H2 gas bypass.
  • the hydrogen gas inlet channel seal insert 320a and the hydrogen gas outlet channel seal insert 320b may be affixed or otherwise coupled adjacent to the hydrogen gas inlet channel section 318a and the hydrogen gas outlet channel section 318b, respectively, on a side of the plate 304 including the carbon foam 306, the positive electrode 308, and the negative electrode 310.
  • the hydrogen gas inlet channel seal insert 320a and the hydrogen gas outlet channel seal insert 320b may be coincident with an x-y plane of the negative electrode 310 such that the hydrogen gas inlet channel seal insert 320a and the hydrogen gas outlet channel seal insert 320b may extend from a locus of affixation or coupling with the plate 304 and partially overlap the positive electrode 308.
  • the plurality of sealing inserts may further include each of a hydrogen gas inlet channel O-ring 322a and a hydrogen gas outlet channel O-ring 322b for respectively sealing an interface of the hydrogen gas inlet channel section 318a with a hydrogen gas inlet channel section of another electrode assembly and an interface of the hydrogen gas outlet channel section 318b with a hydrogen gas outlet channel section of another electrode assembly.
  • the hydrogen gas inlet channel O-ring 322a and the hydrogen gas outlet channel O- ring 322b may be affixed or otherwise coupled to the plate 304 so as to respectively circumscribe the hydrogen gas inlet channel section 318a and the hydrogen gas outlet channel section 318b.
  • the plurality of sealing inserts may further include an overboard O-ring 324 for sealing an interface of the electrode assembly 302 with another electrode assembly at outer edges thereof.
  • the overboard O-ring 324 may be affixed or otherwise coupled to the plate 304 so as to circumscribe each of the electrolyte inlet well 312, the plurality of electrolyte inlet passages 314a, the berm 314b, the electrolyte outlet channel section 316, the hydrogen gas inlet channel section 318a, and the hydrogen gas outlet channel section 318b.
  • the carbon foam 306 may be positioned in a cavity 326 of the plate 304 between the berm 314b and the electrolyte outlet channel section 316 along the y-axis and between the hydrogen gas inlet channel section 318a and the hydrogen gas outlet channel section 318b along the x-axis. Specifically, the carbon foam 306 may be positioned in face-sharing contact with a side of the plate 304 forming a base of the cavity 326. In some examples, the carbon foam 306 may be formed as a continuous monolithic piece, while in other examples, the carbon foam 306 may be formed as two or more carbon foam sections.
  • the carbon foam 306 may be conductive, permeable, and porous, providing a distribution field for the electrolyte being gravity fed therethrough from the plurality of electrolyte inlet passages 314a.
  • a pore distribution of the carbon foam 306 may be between 10 and 100 PPI.
  • the pore distribution may be 30 PPI.
  • a permeability of the carbon foam 306 may be between 0.02 and 0.5 mm 2 . As such, each of the pore distribution and the permeability, in addition to an overall size, of the carbon foam 306 may be selected to target a relatively small pressure drop and thereby induce convection of the electrolyte from the carbon foam 306 into the positive electrode 308.
  • the pressure drop may be targeted to between 2 to 3 mm of electrolyte head rise.
  • the carbon foam 306 may be replaced with a flow field plate configured to transport the electrolyte into the positive electrode 308 via convection induced by a flow field configuration of the flow field plate.
  • the flow field plate may be fluidically coupled to each of the plurality of electrolyte inlet passages 314a and the electrolyte outlet channel section 316.
  • the flow field plate may be integrally formed in the plate 304 of the electrode assembly 302, positioned beneath the positive electrode 308 with respect to the z-axis. In other examples, the flow field plate may be a separate, removable component.
  • the flow field configuration may be an interdigitated flow field configuration, a partially interdigitated flow field configuration, or a serpentine flow field configuration.
  • each electrode assembly 302 may interface with a flow field configuration of like configuration (e.g., interdigitated, partially interdigitated, serpentine, etc.) as each other electrode assembly 302.
  • a number of different flow field configurations may be provided among the electrode assemblies 302 in the stack of electrode assemblies dependent upon a location of a given electrode assembly 302 in the rebalancing cell 202 of FIGS.2A and 2B.
  • the electrolyte may be directed from the electrolyte inlet port (e.g., the electrolyte inlet port 206 of FIGS.2A and 2B) to the flow field plates respectively interfacing with the positive electrodes 308 in the stack of electrode assemblies, the flow field plates being configured in interdigitated flow field configurations, partially interdigitated flow field configurations, serpentine flow field configurations, or a combination thereof.
  • the electrolyte inlet port e.g., the electrolyte inlet port 206 of FIGS.2A and 2B
  • the flow field plates being configured in interdigitated flow field configurations, partially interdigitated flow field configurations, serpentine flow field configurations, or a combination thereof.
  • another flow field plate (also referred to herein as a “hydrogen gas flow field plate”) may interface with the negative electrode 310 opposite from the positive electrode 308 with respect to the z-axis.
  • the electrolyte flow field plate may be included (e.g., replacing the carbon foam 306) and no hydrogen gas flow field plate may be present.
  • the hydrogen gas flow field plate may be included (e.g., interfacing with the negative electrode 310) and no electrolyte flow field plate may be present.
  • the positive electrode 308 may be positioned in the cavity 326 in face-sharing contact with a side of the carbon foam 306 opposite from the plate 304 along the z-axis.
  • the positive electrode 308 may be a wicking conductive carbon felt, sponge, or mesh which may bring the electrolyte flowing through the carbon foam 306 into contact with the negative electrode 310 via capillary action.
  • the positive electrode 308 may be conductive and porous (though less porous than the carbon foam 306 in such examples).
  • the electrolyte may be wicked into the positive electrode 308 when the porosity of the carbon foam 306 may be within a predefined range (e.g., below an upper threshold porosity so as to retain enough solid material to promote wicking up and into the positive electrode 308 and above a lower threshold porosity so as to not impede electrolyte flow through the carbon foam 306).
  • a predefined range e.g., below an upper threshold porosity so as to retain enough solid material to promote wicking up and into the positive electrode 308 and above a lower threshold porosity so as to not impede electrolyte flow through the carbon foam 306.
  • each of a sorptivity of the positive electrode 308 may decrease and a permeability of the positive electrode 308 may increase with an increasing porosity of the positive electrode 308 (e.g., at least until too little solid material of the positive electrode 308 remains to promote wicking of the electrolyte, such as when a threshold porosity of the positive electrode 308 is reached).
  • surfaces of the positive electrode 308 may be sufficiently hydrophilic for desirable rebalancing cell operation (e.g., by facilitating thorough electrolyte wetting and thereby forming an ionically conductive medium).
  • an overall hydrophilicity of the positive electrode 308 may be increased by coating or treating the surfaces thereof.
  • each of the positive electrode 308 and the negative electrode 310 may be formed as a continuous monolithic piece (e.g., as opposed to discrete particles or a plurality of pieces), such that interphase mass-transport losses across boundary layer films may be reduced when bringing the electrolyte into contact with the H2 gas at the catalytic surfaces of the negative electrode 310, thereby promoting ion and proton movement.
  • a packed bed configuration including discretely packed catalyst particles may include mass-transport limiting boundary layer films surrounding each individual particle, thereby reducing a rate of mass- transport of the electrolyte from a bulk thereof to surfaces of the particles.
  • the negative electrode 310 may be positioned in the cavity 326 in face-sharing contact with a side of the positive electrode 308 opposite from the carbon foam 306 along the z-axis, such that a three-phase contact interface between the (wicked) electrolyte, the catalytic surfaces of the negative electrode 310, and the H 2 gas may be formed for proton (e.g., H + ) and ion movement (H3O + ) therethrough.
  • the positive electrode 308 may reduce an overall electronic resistance by providing a conductive path for electrons to move into the electrolyte front and reduce Fe 3+ ions thereat.
  • the negative electrode 310 may be a porous non- conductive material or a conductive carbon substrate with a metal catalyst coated thereon.
  • the porous non-conductive material may include polytetrafluoroethylene (PTFE), polypropylene, or the like.
  • the conductive carbon substrate may include carbon cloth or carbon paper.
  • the metal catalyst may include a precious metal catalyst. In some examples, the precious metal catalyst may include Pt.
  • the precious metal catalyst may include Pd, Rh, Ru, Ir, Ta, or alloys thereof.
  • a relatively small amount e.g., 0.2 to 0.5 wt%) of the precious metal catalyst supported on the conductive carbon substrate may be employed for cost considerations.
  • the amount of the precious metal catalyst may not be particularly limited and may be selected based on one or more of a desired rate of reaction for the rebalancing cell and an expected lifetime of the rebalancing cell.
  • alloys included in the precious metal catalyst may be utilized to reduce cost and increase a corrosion stability of the precious metal catalyst. For example, 10% addition of Rh to Pt may reduce corrosion of Pt by Fe 3+ by over 98%.
  • the metal catalyst may include a non-precious metal catalyst selected for stability in ferric solution and other such acidic environments (e.g., molybdenum sulfide).
  • the negative electrode 310 may include carbon cloth coated with 1.0 mg/cm 2 Pt and may include a microporous layer bound with a polytetrafluoroethylene (PTFE) binder (e.g., for hydrophobicity). Indeed, inclusion of the PTFE binder may increase a durability of rebalancing cell performance over extended durations relative to electrode assemblies formed using other binders.
  • PTFE polytetrafluoroethylene
  • soaking of the negative electrode 310 may eventually result in corrosion of the precious metal catalyst.
  • the electrode assembly 302 (along with the stack of electrode assemblies and the entire rebalancing cell) may be tilted or inclined with respect to a surface on which the rebalancing cell rests (e.g., the z-axis may be non-parallel with a direction of gravity) such that the precious metal catalyst may remain relatively dry as flow of the electrolyte is drawn through the carbon foam 306 toward the electrolyte outlet channel section 316 via gravity feeding.
  • the electrode assembly 302 may either be horizontal or inclined with respect to the surface on which the rebalancing cell rests at an angle of between 0° and 30°.
  • the electrode assembly 302 including each of the carbon foam 306, the positive electrode 308, and the negative electrode 310, may be under compression along the z-axis, with the positive electrode 308 having a greater deflection than the carbon foam 306 and the negative electrode 310 under a given compressive pressure. Accordingly, a depth of the cavity 326 may be selected based on a thickness of the carbon foam 306, a thickness of the positive electrode 308, a desired compression of the positive electrode 308, and a thickness of the negative electrode 310.
  • the depth of the cavity 326 may be selected to be greater than a lower threshold depth of a sum of the thickness of the carbon foam 306 after substantially complete compression thereof and the thickness of the positive electrode 308 after substantially complete compression thereof (to avoid overstressing and crushing of the carbon foam 306, which may impede electrolyte flow) and less than an upper threshold depth of a sum of the thickness of the carbon foam 306 and the thickness of the positive electrode 308 (to avoid zero compression of the positive electrode 308 and possibly a gap, which may result in insufficient contact of the H 2 gas and the electrolyte).
  • the thickness of the carbon foam 306 may be between 2 and 10 mm
  • the thickness of the positive electrode 308 may be between 1 and 10 mm
  • the desired compression of the positive electrode 308 may be between 0 and 2.34 mm (so as to achieve the desired compressive pressure of 0 to 0.09 MPa)
  • the thickness of the negative electrode 310 may be between 0.2 and 1 mm, such that the depth of the cavity 326 may be between 0.86 and 21 mm.
  • the thickness of the positive electrode 308 may be 20% to 120% of the thickness of the carbon foam 306.
  • the thickness of the positive electrode 308 may be 100% to 110% of the thickness of the carbon foam 306.
  • the depth of the cavity 326 may further depend upon a crush strength of the carbon foam 306 (e.g., the depth of the cavity 326 may be increased with decreasing crush strength).
  • a foam crush factor of safety (FOS) may be 5.78 when the depth of the cavity 326 is 9.2 mm (e.g., when the desired compression of the positive electrode is 0.4 mm).
  • the foam crush FOS may have a minimum value of 0.34 in some examples, where foam crush FOS values less than 1 may indicate that at least some crushing is expected.
  • the crush strength of the carbon foam 306 may be reduced by heat treatment of the carbon foam 306 during manufacturing thereof (from 0.08 MPa to 0.03 MPa, in one example).
  • the electrode assembly 302 may be configured such that the depth of the cavity 326 is as low as possible (e.g., within the above constraints), as generally thinner electrode assemblies 302 may result in a reduced overall size of the rebalancing cell and a reduced electrical resistance across the electrode assembly 302 (e.g., as the electrolyte flow may be closer to the negative electrode 310).
  • the electrode assembly 302 may include a sequential stacking of the carbon foam 306 and an interfacing pair of the positive electrode 308 and the negative electrode 310 being in face-sharing contact with one another and being continuously electrically conductive.
  • a first interface may be formed between the positive electrode 308 and the carbon foam 306 and a second interface may be formed between the positive electrode 308 and the negative electrode 310, the second interface being opposite to the first interface across the positive electrode 308, and each of the carbon foam 306, the positive electrode 308, and the negative electrode 310 may be electrically conductive.
  • the electrode assembly 302 may be internally shorted, such that electric current flowing through the electrode assembly 302 may not be channeled through an external load.
  • forced convection may induce flow of the H2 gas into the electrode assembly 302 and across the negative electrode 310 (e.g., via a flow field plate interfacing with the negative electrode 310; not shown at FIG.3).
  • the H2 gas may react with the catalytic surface of the negative electrode 310 via equation (4a) (e.g., the reverse reaction of equation (1)): 1 ⁇ 2H 2 ⁇ H + + + e- (anodic half reaction) (4a)
  • the proton (H + ) and the electron (e-) may be conducted across the negative electrode 310 and into the positive electrode 308.
  • the electrolyte, directed through the electrode assembly 302 via the carbon foam 306, may be wicked into the positive electrode 308.
  • ⁇ mt and ⁇ act may be assumed to be negligible.
  • the performance of the electrode assembly 302 may further be limited based on a front location of the electrolyte within the carbon felt and therefore the distribution of the electrolyte across the carbon foam 306 and an amount of the electrolyte wicked into the carbon felt forming the positive electrode 308.
  • v rebalancing may have a maximum value of 113 mol/m 2 hr.
  • FIGS.4A and 4B a cross-sectional view 400 and a magnified inset view 450 are respectively shown, each of the cross-sectional view 400 and the magnified inset view 450 depicting exemplary aspects of H 2 gas flow within the rebalancing cell 202.
  • the magnified inset view 450 magnifies a portion of the cross-sectional view 400 delimited by a dashed ellipse 410. As shown in FIGS.
  • the rebalancing cell 202 may include an electrode assembly stack 402 formed as a stack of individual electrode assemblies 302 aligned such that the hydrogen gas inlet channel section 318a of each electrode assembly 302 forms a continuous hydrogen gas inlet channel 404 with the hydrogen gas inlet channel section 318a of each other electrode assembly 302.
  • a hydrogen gas inlet plenum 406 may further be included in the hydrogen gas inlet channel 404, the hydrogen gas inlet plenum 406 fluidically coupling the hydrogen gas inlet channel 404 to the hydrogen gas inlet port 210.
  • Respective hydrogen gas inlet channel O-rings 322a and overboard O-rings 324 may seal the hydrogen gas inlet channel 404 at interfaces between pairs of the electrode assemblies 302.
  • cut portions of the rebalancing cell 202 are depicted in the cross-sectional view 400 and the magnified inset view 450 for detail, and that additional features of the rebalancing cell 202 (e.g., shown in FIGS. 2A and 2B) may not be depicted.
  • greater or fewer electrode assemblies 302 may be included in the electrode assembly stack 402 than shown in the cross- sectional view 400 for a given application (however, in some examples, scale-up performance may be substantially insensitive to H 2 gas flow at or below 50% H 2 gas utilization).
  • structural features of the hydrogen gas inlet channel 404 and adjacent components are described in detail with reference to FIGS.
  • a corresponding hydrogen gas outlet channel e.g., formed by aligning a hydrogen gas outlet channel section 318b (see FIG. 3) of each electrode assembly 302] and adjacent components may be similarly configured (excepting that the hydrogen gas outlet channel may be dead ended or that a hydrogen gas outlet plenum included in the hydrogen gas outlet channel may be positioned opposite to the hydrogen gas inlet plenum 406 along the x- and z-axes).
  • the H 2 gas may enter the hydrogen gas inlet channel 404 via the hydrogen gas inlet port 210, flowing first into the hydrogen gas inlet plenum 406 and then sequentially through the hydrogen gas inlet channel sections 318a in a positive direction along the z-axis.
  • a size and a shape of the hydrogen gas inlet plenum 406 is not particularly limited, though a minimum size (e.g., a minimum volume, a minimum flow path width) of the hydrogen gas inlet plenum 406 may be selected to avoid relatively high flow velocity and pressure drop resulting in poor H 2 gas distribution.
  • the sloped support 220 may tilt the rebalancing cell 202 such that the hydrogen gas inlet channel 404 extends along the positive direction of the z-axis away from a direction of gravity (though not directly opposite to the direction of gravity, as discussed in detail above with reference to FIGS.2A and 2B), and the H 2 gas may convect along the hydrogen gas inlet channel 404 along the positive direction of the z- axis.
  • H 2 gas may flow from the hydrogen gas inlet channel 404 across the hydrogen gas inlet channel seal insert 320a of each respective electrode assembly 302 and into one or more hydrogen gas inlet passages 452 fluidically coupled to the hydrogen gas inlet channel 404 and interfacing with each respective electrode assembly 302.
  • a surface of the hydrogen gas inlet channel seal insert 320a of a given electrode assembly 302 opposite to the one or more hydrogen gas inlet passages 452 of the given electrode assembly 302 may be coincident with the same x-y plane as a surface of the negative electrode 310 of the given electrode assembly 302 opposite to the one or more hydrogen gas inlet passages 452 of the given electrode assembly.
  • the hydrogen gas inlet channel seal insert 320a of the given electrode assembly 302 may extend from a locus of affixation or coupling with the plate 304 of the given electrode assembly 302 and partially overlap the positive electrode 308 of the given electrode assembly 302 along the z-axis, thereby assisting in sealing the positive electrode 308 at an edge thereof.
  • the one or more hydrogen gas inlet passages 452 may not be wholly included in any given electrode assembly 302 and instead may be formed as one or more gaps between adjacent pairs of electrode assemblies 302 in the electrode assembly stack 402.
  • the one or more hydrogen gas inlet passages 452 interfacing with a given electrode assembly 302 may be configured in a flow field configuration, such that the H2 gas may be forcibly convected into the one or more hydrogen gas inlet passages 452 interfacing with the given electrode assembly 302.
  • the one or more hydrogen gas inlet passages 452 as configured in the flow field configuration may be formed from a flow field plate interfacing with the negative electrode 310 of the given electrode assembly 302.
  • the flow field plate interfacing with the negative electrode 310 of the given electrode assembly 302 may be integrally formed in the plate 304 of an adjacent electrode assembly 302, positioned beneath the carbon foam 306 of the adjacent electrode assembly 302 with respect to the z-axis.
  • the flow field plate interfacing with the negative electrode 310 of the given electrode assembly 302 may be a separate, removable component.
  • a topmost flow field plate with respect to the z-axis may not be integrally formed with any electrode assembly 302 and may instead be included in the rebalancing cell 202 as either a separate, removable component or an integral feature of another component (e.g., the cell enclosure 204 of FIGS.2A and 2B).
  • the flow field configuration may be an interdigitated flow field configuration, a partially interdigitated flow field configuration, or a serpentine flow field configuration.
  • each electrode assembly 302 may interface with a flow field configuration of like configuration (e.g., interdigitated, partially interdigitated, serpentine, etc.) as each other electrode assembly 302.
  • a number of different flow field configurations may be provided among the electrode assemblies 302 of the electrode assembly stack 402 (e.g., dependent upon a location of a given electrode assembly 302 in the rebalancing cell 202).
  • the H 2 gas may be directed from the hydrogen gas inlet port 210 to the flow field plates respectively interfacing with the negative electrodes 310 of the electrode assembly stack 402, the flow field plates being configured in interdigitated flow field configurations, partially interdigitated flow field configurations, serpentine flow field configurations, or a combination thereof.
  • the H2 gas may be convected across the negative electrodes 310 of the electrode assembly stack 402 (e.g., at a flow rate of 10 to 50 l/min per m 2 of the catalytic surfaces of the negative electrode 310).
  • the flow field plates interfacing with the respective electrode assemblies 302 may assist in the convection and distribute the H2 gas across the respective negative electrodes 310.
  • the H2 gas may react with the catalytic surfaces of the negative electrodes 310 of the electrode assembly stack 402 in an anodic half reaction (see equation (4a)) to generate protons and electrons, which may then flow towards respective positive electrodes 308 and carbon foams 306.
  • at least some of the H2 gas may remain unreacted and may flow across the negative electrodes 310 of the electrode assembly stack 402 along the arrows 408c as well.
  • FIGS.4A and 4B schematic views 500, 520, 540, and 560 are respectively shown, the schematic views 500, 520, 540, and 560 respectively depicting an exemplary interdigitated flow field configuration, an exemplary partially interdigitated flow field configuration, a first exemplary serpentine flow field configuration, and a second exemplary serpentine flow field configuration.
  • the one or more hydrogen gas inlet passages 452 of FIGS.4A and 4B may be formed from a flow field plate configured as any of the exemplary flow field configurations of FIGS.5A-5D for a given electrode assembly.
  • FIGS. 5A-5D may be replaced with a flow field plate configured as any of the exemplary flow field configurations of FIGS. 5A-5D for a given electrode assembly.
  • a set of reference axes 501 is provided for describing relative positioning of the components shown and for comparison between the views of FIGS.5A-5D, the axes 501 indicating an x-axis, a y-axis, and a z-axis. It will be appreciated that the relative dimensions shown in FIGS. 5A-5D are exemplary and that other flow field configurations are considered within the scope of the present disclosure (e.g., having wider passages, a greater number of passages or bends therein, etc.).
  • passages forming the flow field configurations may include a series of steps therein (e.g., eight steps, though a total number of the steps may be increased or decreased to alter fluid diffusion and thereby enhance performance for a given application) incrementally extending in height from an inlet of the passage to an outlet or end of the passage (e.g., from substantially zero height to at or near a total depth of the passage).
  • steps therein e.g., eight steps, though a total number of the steps may be increased or decreased to alter fluid diffusion and thereby enhance performance for a given application
  • incrementally extending in height from an inlet of the passage to an outlet or end of the passage e.g., from substantially zero height to at or near a total depth of the passage.
  • the exemplary interdigitated flow field configuration may include a first inlet channel 506a and a second inlet channel 506b.
  • a fluid e.g., H2 gas, electrolyte
  • H2 gas, electrolyte may flow through each of the first inlet channel 506a and second inlet channel 506b parallel to the z-axis, wherefrom the fluid may be forcibly convected over end walls 508 and into passages 502 of the interdigitated flow field configuration parallel to the x-axis (as indicated by arrows 504).
  • each of the passages 502 may be open to one of the first and second inlet channels 506a and 506b.
  • the second inlet channel 506b may be fluidically coupled to the first inlet channel 506a elsewhere.
  • the second inlet channel 506b may serve as an outlet channel for the fluid (e.g., the fluid may flow first through the first inlet channel 506a and then through the second inlet channel 506b following passage of the fluid through the porous medium).
  • the outlet channel for the fluid may not be either of the inlet channels 506a, 506b.
  • the outlet channel may be a pressure release outlet port, such as the pressure release outlet port 214 of FIG.2A, through which the fluid may flow following passage of the fluid through the porous medium.
  • the fluid may sequentially pass through the negative electrode 310, enter flowing electrolyte on the other side of the negative electrode 310, and be expelled via the pressure release outlet port 214 (fluidically coupled to the flowing electrolyte).
  • the exemplary partially interdigitated flow field configuration may include a first inlet channel 526a and a second inlet channel 526b.
  • a fluid e.g., H2 gas, electrolyte
  • H2 gas, electrolyte may flow through each of the first and second inlet channels 526a and 526b parallel to the z-axis, wherefrom the fluid may be forcibly convected into constricted inlets 522a bisecting end walls 528 of passages 522 of the partially interdigitated flow field configuration parallel to the x-axis (as indicated by arrows 524).
  • the exemplary partially interdigitated flow field configuration interfaces with a porous medium (such as the positive electrode 308 or the negative electrode 310 of FIGS.3-4B), and though each of the passages 522 may be open to each of the first and second inlet channels 526a and 526b, substantially all of the fluid may pass into the porous medium after being forcibly convected into the passages 522 via the constricted inlets 522a (e.g., rather than passing from one of the inlet channels 526a, 526b to the other).
  • a porous medium such as the positive electrode 308 or the negative electrode 310 of FIGS.3-4B
  • a thickness of each of the constricted inlets 522a may be variable, ranging from a greatest thickness of a corresponding passage 522 (e.g., a straight-channel flow field configuration, wherein the inlets 522a are substantially unconstricted) to substantially zero thickness (e.g., a fully interdigitated flow field configuration, such as the exemplary interdigitated flow field configuration of FIG.5A).
  • the first exemplary serpentine flow field configuration may include an inlet channel 546a and an outlet channel 546b.
  • a fluid (e.g., H 2 gas, electrolyte) may flow through the inlet channel 546a parallel to the z-axis, wherefrom the fluid may be forcibly convected into an inlet 542a of a serpentine passage 542 of the first exemplary flow field configuration parallel to the x-axis.
  • the fluid may flow along the serpentine passage 542 parallel to the x- and y-axes, altering direction at 90° bends therein until the fluid is expelled from the outlet 542b of the serpentine passage 542 into the outlet channel 546b.
  • the first exemplary serpentine flow field configuration may include longer straight sections of the serpentine passage 542 parallel to the y-axis and shorter straight sections (e.g., bases of U-bends) of the serpentine passage 542 parallel to the x-axis.
  • multiple serpentine passages 542 of like or similar configuration may fluidically couple the inlet channel 546a to the outlet channel 546b.
  • a porous medium such as the positive electrode 308 or the negative electrode 310 of FIGS.
  • the serpentine passage 542 may be open to each of the inlet channel 546a and the outlet channel 546b, substantially all of the fluid may pass into the porous medium after being forcibly convected into the serpentine passage 542 via the inlet 542a (e.g., rather than passing from the inlet channel 546a to the outlet channel 546b).
  • the serpentine passage 542 may not include the outlet 542b and thus may not fluidically couple to the outlet channel 546b (e.g., such as when the first exemplary serpentine flow field configuration is dead ended).
  • the second exemplary serpentine flow field configuration may include an inlet channel 566a and an outlet channel 566b.
  • a fluid (e.g., H 2 gas, electrolyte) may flow through the inlet channel 566a parallel to the z-axis, wherefrom the fluid may be forcibly convected into an inlet 562a of a serpentine passage 562 of the second exemplary flow field configuration parallel to the x-axis.
  • the fluid may flow along the serpentine passage 562 parallel to the x- and y-axes, altering direction at 90° bends therein until the fluid is expelled from the outlet 562b of the serpentine passage 562 into the outlet channel 566b.
  • the second exemplary serpentine flow field configuration may include longer straight sections of the serpentine passage 562 parallel to the x-axis and shorter straight sections (e.g., bases of U-bends) of the serpentine passage 562 parallel to the y-axis.
  • multiple serpentine passages 562 of like or similar configuration may fluidically couple the inlet channel 566a to the outlet channel 566b.
  • a porous medium such as the positive electrode 308 or the negative electrode 310 of FIGS.
  • the serpentine passage 562 may be open to each of the inlet channel 566a and the outlet channel 566b, substantially all of the fluid may pass into the porous medium after being forcibly convected into the serpentine passage 562 via the inlet 562a (e.g., rather than passing from the inlet channel 566a to the outlet channel 566b).
  • the serpentine passage 562 may not include the outlet 562b and thus may not fluidically couple to the outlet channel 566b (e.g., such as when the second exemplary serpentine flow field configuration is dead ended).
  • FIGS.6A and 6B a cross-sectional view 600 and a magnified inset view 650 are respectively shown, each of the cross-sectional view 600 and the magnified inset view 650 depicting exemplary aspects of electrolyte flow within the rebalancing cell 202.
  • the magnified inset view 650 magnifies a portion of the cross-sectional view 600 delimited by a dashed ellipse 610.
  • the rebalancing cell 202 may include one or more electrolyte inlet channels 614 fluidically coupled to the electrolyte inlet wells 312 included in the individual electrode assemblies 302 of the electrode assembly stack 402.
  • Each of the one or more electrolyte inlet channels 614 may be fluidically coupled to an electrolyte inlet plenum 606a located above the electrode assembly stack 402 with respect to the z-axis via a respective nozzle or orifice 612 modulating, restricting, or otherwise controlling flow of the electrolyte into the respective electrolyte inlet channel 614.
  • the electrolyte inlet plenum 606a may further be fluidically coupled to the electrolyte inlet port (e.g., the electrolyte inlet port 206 of FIGS.2A and 2B; not shown at FIGS.6A and 6B).
  • the electrode assembly stack 402 may further be formed as a stack of the individual electrode assemblies 302 aligned such that the electrolyte outlet channel section 316 of each electrode assembly forms a continuous electrolyte outlet channel 604 with the electrolyte outlet channel section 316 of each electrode assembly 302, the electrolyte outlet channel 604 being parallel to the one or more electrolyte inlet channels 614 and to the z-axis and on an opposite end of the rebalancing cell 202 from the one or more electrolyte inlet channels 614 with respect to the y-axis.
  • An electrolyte outlet plenum 606b may further be included in the electrolyte outlet channel 604, the electrolyte outlet plenum 606b fluidically coupling the electrolyte outlet channel 604 to the electrolyte outlet port 208.
  • Respective overboard O-rings 324 may seal the electrolyte outlet channel 604 at interfaces between pairs of electrode assemblies 302. It will be appreciated that cut portions of the rebalancing cell 202 are depicted in the cross-sectional view 600 and the magnified inset view 650 for detail, and that additional features of the rebalancing cell 202 (e.g., shown in FIGS. 2A and 2B) may not be depicted.
  • the electrolyte may enter the electrolyte inlet plenum 606a via the electrolyte inlet port, wherefrom the electrolyte may be directed into the one or more electrolyte inlet channels 614 via the one or more orifices 612, respectively.
  • a cross-sectional shape of the electrolyte inlet plenum 606a may be selected for ease of machining.
  • the cross- sectional shape of the electrolyte inlet plenum 606a may be rectangular.
  • the cross-sectional shape of the electrolyte inlet plenum 606a may be circular.
  • a size of the electrolyte inlet plenum 606a may be selected to realize a relatively low pressure drop upon entry of the electrolyte into the rebalancing cell 202.
  • a size of each of the one or more orifices 612 may be between 3 and 10 mm, as dependent on a total number of electrode assemblies 302 in the electrode assembly stack 402, an overall size of the rebalancing cell 202, and an electrolyte flow path design. The size and overall configuration of each of the one or more orifices 612 may be selected to maintain substantially even electrolyte flow throughout each electrode assembly 302 of the electrode assembly stack 402.
  • each of the one or more electrolyte inlet channels 614 may be a continuous and unbroken channel configured adjacent to the electrode assembly stack 402.
  • each electrode assembly 302 of the electrode assembly stack 402 may include one or more electrolyte inlet channel sections corresponding to the one or more electrolyte inlet channels 614, respectively.
  • the electrode assemblies 302 of the electrode assembly stack 402 may be aligned such that the one or more electrolyte inlet channel sections of each electrode assembly 302 respectively form the one or more electrolyte inlet channels 614 with the one or more electrolyte inlet channel sections of each other electrode assembly 302.
  • the one or more electrolyte inlet channels 614 may include a plurality of electrolyte inlet channels 614 and the one or more orifices 612 may include a plurality of orifices 612 respectively fluidically coupled to the plurality of electrolyte inlet channels 614, such that an electrolyte inlet manifold may be formed.
  • a single nearest electrolyte inlet channel 614 of the plurality of electrolyte inlet channels 614 is visible, obscuring each other electrolyte inlet channel 614 of the plurality of electrolyte inlet channels 614 aligned therewith parallel to the x-axis.
  • each of the plurality of electrolyte inlet channels 614 forming the electrolyte inlet manifold may be respectively fluidically coupled to a single electrode assembly 302 of the electrode assembly stack 402 so as to evenly flow the electrolyte across the electrode assemblies 302 of the electrode assembly stack (e.g., at an electrolyte flow rate of ⁇ 10-40 L/min per m 2 of the catalytic surfaces of the negative electrode 310).
  • the electrolyte entering the electrolyte inlet plenum 606a may have an adjustable flow rate (e.g., by a controller of the redox flow battery system, such as the controller 88 of FIG.
  • each of the plurality of electrolyte inlet channels 614 may be fluidically coupled to each electrode assembly 302 of the electrode assembly stack 402 so as to evenly distribute the electrolyte across the electrode assembly stack 402 with respect to both the x- and y-axes.
  • the one or more electrolyte inlet channels 614 may include one electrolyte inlet channel 614 which may be fluidically coupled to each electrode assembly 302 of the electrode assembly stack 402.
  • a cross-sectional shape of each of the one or more electrolyte inlet channels 614 may be a circle.
  • the cross-sectional shape of each of the one or more electrolyte inlet channels 614 is not particularly limited and other geometric shapes may be employed.
  • a size of each of the one or more electrolyte inlet channels 614 may be selected to realize a relatively low pressure drop for the electrolyte flow rate of ⁇ 10-40 L/min per m 2 of the catalytic surfaces of the negative electrode 310 (e.g., relatively small sizes may result in poor distribution of the electrolyte) while maintaining practical size considerations of the rebalancing cell 202 as a whole (e.g., relatively large sizes may result in an undesirably large rebalancing cell 202).
  • the cross-sectional shape of each of the one or more electrolyte inlet channels 614 may be a circle having a diameter of between 10 and 30 mm.
  • a pressure therein may be substantially similar to a pressure of an electrolyte source (e.g., the negative and positive electrode compartments 22 and 20 and/or the integrated multi-chambered electrolyte storage tank 110 of FIG.1), such that gravity may substantially exclusively drive electrolyte flow through the one or more electrolyte inlet channels 614.
  • the electrolyte may flow through the one or more electrolyte inlet channels 614 in a negative direction along the z-axis and into the electrolyte inlet wells 312 of the electrode assembly stack 402.
  • the sloped support 220 may tilt the rebalancing cell 202 such that the z-axis is offset from the axis g coincident with the direction of gravity, and the electrolyte may flow through the carbon foams 306 of the electrode assembly stack 402 via gravity feeding (as indicated by arrows 608b).
  • the electrolyte may flow through the carbon foams 306 of the electrode assembly stack 402 via gravity feeding (as indicated by arrows 608b).
  • arrows 608c while flowing through the carbon foams 306 of the electrode assembly stack 402, at least some of the electrolyte may be induced into the positive electrodes 308 of the electrode assembly stack 402 towards the negative electrodes 310 of the electrode assembly stack 402 via capillary action.
  • Fe 3+ ions in the electrolyte may be reduced by electrons flowing through the negative electrodes 310 of the electrode assembly stack 402 in a cathodic half reaction (see equation (4b)) to generate Fe 2+ ions.
  • a depth 652 of the cavity e.g., the cavity 326 of FIG.3 may be selected such that the positive electrode 308 is at least partially compressed without excessively compressing the carbon foam 306 (which may buckle and degrade a foam structure thereof).
  • a thickness 654 of the adjacent positive electrode 308 may be decreased (e.g., by about 10%) relative to when the positive electrode 308 is fully uncompressed.
  • the thickness 654 of the positive electrode 308 may be 20% to 120% of the thickness 656 of the carbon foam 306, where each of the thickness 654 of the positive electrode 308 and the thickness 656 of the carbon foam 306 may be selected based on structural considerations such as the permeability of the carbon foam 306, an overall size of the positive electrode 308, etc.
  • the thickness 654 of the positive electrode 308 may be 100% to 110% of the thickness 656 of the carbon foam 306.
  • the electrolyte may be directed through electrolyte outlet passages 658 of the electrode assembly stack 402, into the electrolyte outlet channel 604, and out through the electrolyte outlet port 208 therefrom.
  • the electrolyte may flow from the carbon foam 306 through the electrolyte outlet passage 658 and into the electrolyte outlet channel section 316, wherefrom the electrolyte may flow with the direction of gravity (e.g., along the positive direction of the axis g) into the electrolyte outlet plenum 606b (after passing through any further electrolyte outlet channel sections 316 interposed between the given electrode assembly 302 and the electrolyte outlet plenum 606b).
  • the electrolyte may then pass through the electrolyte outlet plenum 606b and into the electrolyte outlet port 208, wherefrom the electrolyte may be expelled from the rebalancing cell 202.
  • the electrolyte may be directed from the electrolyte inlet port (e.g., the electrolyte inlet port 206 of FIGS.2A and 2B; not shown at FIGS.6A and 6B) through the carbon foams 306 of the electrode assembly stack 402 to the electrolyte outlet port 208.
  • an overall size of each of the electrolyte outlet passages 658 may be selected so as to be sufficiently large to generate a suitable pressure drop and to not overfill the electrolyte outlet plenum 606b (which may flood the electrode assemblies 302 at a bottom of the electrode assembly stack 402 with respect to the z-axis).
  • each of the electrolyte outlet passages 658 may depend on an overall size of the electrolyte outlet plenum 606b and an overall number of openings corresponding to the electrolyte outlet port 208.
  • dimensions of the electrolyte outlet plenum 606b may be larger to accommodate an electrolyte outlet port 208 having fewer, larger openings.
  • electrolyte outlet port 208 is positioned on the face of the cell enclosure 204 facing the negative direction of the z-axis
  • larger openings may be accommodated while maintaining a thickness of a lowest electrode assembly 302 along the z-axis and the pressure drop may be further reduced (e.g., as the electrolyte would not flow at a ⁇ 90° angle from the electrolyte outlet plenum 606b to the electrolyte outlet port 208).
  • flow field plates 626 may respectively interface with the electrode assemblies 302 of the electrode assembly stack 402.
  • the flow field plate 626 may interface (e.g., be in face-sharing contact) with the negative electrode 310 of a given electrode assembly 302 and may be integrally formed in the plate 304 of an adjacent electrode assembly 302, positioned beneath the carbon foam 306 of the adjacent electrode assembly 302 with respect to the z-axis.
  • the flow field plate 626 interfacing with the negative electrode 310 of the given electrode assembly 302 may be a separate, removable component.
  • a topmost flow field plate 626 with respect to the z-axis may not be integrally formed with any electrode assembly 302 and may instead be included in the rebalancing cell 202 as either a separate, removable component or an integral feature of another component (e.g., the cell enclosure 204 of FIGS.2A and 2B).
  • the one or more hydrogen gas inlet passages 452, configured to flow the H 2 gas across a given electrode assembly 302 may be formed from the flow field plate 626 interfacing with the negative electrode 310 of the given electrode assembly 302.
  • the one or more hydrogen gas inlet passages 452 may be configured as either a plurality of hydrogen gas inlet passages 452 parallel to one another and the x-axis (e.g., in the interdigitated flow field configuration or the partially interdigitated flow field configuration) or a single, coiled hydrogen gas inlet passage 452 into which the H2 gas may enter parallel to the x- axis (e.g., in the serpentine flow field configuration).
  • the one or more hydrogen gas inlet passages 452 may extend parallel to the x-axis while the electrolyte may flow through the carbon foam 306 of the given electrode assembly 302 parallel to the y-axis (as indicated by the arrows 608b).
  • the H 2 gas may be directed into the electrode assembly stack 402 at a 90° angle from which the electrolyte may be directed into the electrode assembly stack 402.
  • the carbon foam 306 of a given electrode assembly 302 may be replaced with a flow field plate of substantially similar flow field configuration to the flow field plate 626.
  • the flow field configuration of the flow field plate replacing the carbon foam 306 of the given electrode assembly 302 may be oriented in the same direction as the flow field configuration of the flow field plate 626 with respect to the x- and y-axes.
  • the flow field configuration of the flow field plate replacing the carbon foam 306 of the given electrode assembly 302 may be oriented in a different direction as the flow field configuration of the flow field plate 626 (e.g., at a 90° angle, a 180° angle, or a 270° angle) with respect to the x- and y-axes.
  • FIGS. 7A and 7B perspective views 700 and 750 are respectively shown, each of the perspective views 700 and 750 depicting aspects of electrolyte flow through an exemplary electrode assembly 702 for a rebalancing cell of a redox flow battery system.
  • the electrode assembly 702 may include a sequential stacking of a carbon foam 706, a positive electrode 708, and a negative electrode 710, where the carbon foam 706 and the positive electrode 708 may be in face-sharing contact with one another, the positive electrode 708 may be in face- sharing contact with the negative electrode 710, and the sequential stacking may be continuously electrically conductive.
  • a stack of the electrode assemblies 702 may be implemented in the rebalancing cell 202 in place of the electrode assemblies 302 of the electrode assembly stack 402 (see FIGS.2A-4B, 6A, and 6B). Accordingly, the redox flow battery system may be the redox flow battery system 10 of FIG.1.
  • a set of reference axes 701 is provided for describing relative positioning of the components shown and for comparison between the views of FIGS.7A and 7B, the axes 701 indicating an x-axis, a y-axis, and a z-axis.
  • an additional axis g may be parallel with a direction of gravity (e.g., in a positive direction along the axis g) and a vertical direction (e.g., in a negative direction along the axis g and opposite to the direction of gravity).
  • the electrode assembly 702 may include a sequential stacking of a carbon foam 706, a positive electrode 708, and a negative electrode 710 on a plate 704, where the plate 704 may be in face-sharing contact with the carbon foam 706, the carbon foam 706 may be in face- sharing contact with the positive electrode 708, and the positive electrode 708 may be in face- sharing contact with the negative electrode 710.
  • the carbon foam 706 may be retained in place by a plurality of holders 766. Accordingly, an overall size of the carbon foam 706 may be selected to be clearance fit to the plurality of holders 766.
  • Each of the carbon foam 706 and the positive electrode 708 may be porous and continuously electrically conductive with the negative electrode 710.
  • the carbon foam 706 may be an activated conductive carbon foam
  • the positive electrode 708 may be a conductive carbon felt
  • the negative electrode 710 may be a conductive carbon substrate with a Pt catalyst coated thereon.
  • the carbon foam 706, the positive electrode 708, and the negative electrode 710 may be the carbon foam 306, the positive electrode 308, and the negative electrode 310 of FIG.3, respectively.
  • the carbon foam 706 may be replaced with a flow field plate for convecting the electrolyte across the electrode assembly 702 and into contact with the positive electrode 708.
  • the plate 704 may include a plurality of inlets and outlets therethrough for directing flows of the H 2 gas and the electrolyte.
  • the plurality of inlets and outlets may include a hydrogen gas inlet channel section 718a for receiving the H2 gas (e.g., from a hydrogen gas inlet port of the rebalancing cell), a hydrogen gas outlet channel section 718b for expelling the H 2 gas (e.g., through a hydrogen gas outlet port of the rebalancing cell), and one or more electrolyte outlet passages 716 for expelling the electrolyte (e.g., through one or more electrolyte outlet ports of the rebalancing cell respectively accepted by and fitted to the one or more electrolyte outlet passages 716, the one or more electrolyte outlet ports configured as one or more fusion-welded plumbing flanges in an exemplary embodiment).
  • a hydrogen gas inlet channel section 718a for receiving the H2 gas (e.g., from a hydrogen gas inlet port of the rebalancing cell)
  • a hydrogen gas outlet channel section 718b for expelling the H 2 gas (e.g., through a hydrogen
  • the electrolyte inlet well 712 may be fluidically coupled to the sequential stacking of the carbon foam 706, the positive electrode 708, and the negative electrode 710 via a plurality of electrolyte inlet passages 714a set in a berm 714b extending parallel to the x-axis.
  • the plurality of electrolyte inlet passages 714a may be distributed across the berm 714b, a length of each of the plurality of electrolyte inlet passages 714a extending parallel to the y-axis.
  • an electrolyte trough 764 may further be interposed between the berm 714b and the sequential stacking of the carbon foam 706, the positive electrode 708, and the negative electrode 710.
  • the electrolyte inlet well 712, the plurality of electrolyte inlet passages 714a, the berm 714b, and the electrolyte trough 764 may be configured for distributing the electrolyte across the sequential stacking of the carbon foam 706, the positive electrode 708, and the negative electrode 710.
  • an overall number of the plurality of electrolyte inlet passages 714a may be selected based on a target pressure drop of between 0.5 to 3 mm of electrolyte head rise (which may in turn be a function of an electrolyte flow rate and an overall size of the electrode assembly 702).
  • a shape of each of the plurality of electrolyte inlet passages 714a may be rectangular (e.g., for ease of manufacturing).
  • the shape of each of the plurality of electrolyte inlet passages 714a is not particularly limited and other geometries may be employed.
  • the electrolyte inlet well 712 may receive the electrolyte from the electrolyte inlet port (e.g., the electrolyte inlet port 206 of FIGS.2A and 2B). As the electrolyte distributes throughout the electrolyte inlet well 712, the electrolyte may collect against the berm 714b and flow thereacross via the plurality of electrolyte inlet passages 714a and into the electrolyte trough 764. As the electrolyte further distributes throughout the electrolyte trough 764, the electrolyte may flow therefrom through the carbon foam 706 (as indicated by arrows 708b).
  • the electrolyte inlet port e.g., the electrolyte inlet port 206 of FIGS.2A and 2B.
  • the positive electrode 708 may wick up (e.g., against the direction of gravity) at least some of the electrolyte towards the negative electrode 710, whereat ions in the electrolyte may be reduced by electrons flowing through the negative electrode 710 (e.g., from decomposition of the H2 gas at the negative electrode 710).
  • the electrolyte may flow through the one or more electrolyte outlet passages 716, wherefrom the electrolyte may be expelled from the rebalancing cell via the electrolyte outlet port (e.g., the electrolyte outlet port 208 of FIGS.2A and 2B).
  • the electrode assembly 702 may be tilted relative to the direction of gravity so as to induce electrolyte flow therethrough along the y-axis via gravity feeding.
  • the z-axis may either be aligned with or offset from the vertical direction opposite to the direction of gravity at an angle of 0° to 30° such that the y-axis may not be orthogonal to the axis g.
  • FIGS. 8A-8D perspective views 800, 825, and 850 and a cross- sectional view 875 are shown in FIGS 8A, 8B, 8C, and 8D respectively, each of the perspective views 800, 825, and 850 and the cross-sectional view 875 depicting a flow field plate 826 of an exemplary electrode assembly 802 for a rebalancing cell of a redox flow battery system are respectively shown.
  • the flow field plate 826 may be integrally formed in a plate 804 of the electrode assembly 802, the flow field plate 826 being configured to convect H 2 gas through passages thereof.
  • a stack of the electrode assemblies 802 may be implemented in a rebalancing cell 202 in place of the electrode assemblies 302 of the electrode assembly stack 402 (see FIGS.2A-4B, 6A, and 6B).
  • the redox flow battery system may be the redox flow battery system 10 of FIG.1.
  • a set of reference axes 801 is provided for describing relative positioning of the components shown and for comparison between the views of FIGS.8A-8D, the axes 801 indicating an x-axis, a y-axis, and a z-axis.
  • the flow field plate 826 may be formed in the plate 804 adjacent to an electrolyte outlet channel section 816 of the plate 804 and in fluidic communication with each of a hydrogen gas inlet channel section 818a and a hydrogen gas outlet channel section 818b of the plate 804.
  • the flow field plate 826 may include a plurality of inlet passages 852a, each of the plurality of inlet passages 852a being fluidically coupled to the hydrogen gas inlet channel section 818a.
  • the flow field plate 826 may further include a plurality of outlet passages 852b, each of the plurality of outlet passages 852b being fluidically coupled to a hydrogen gas outlet channel section 818b of the plate 804.
  • the plurality of inlet passages 852a may be interdigitated with the plurality of outlet passages 852b, each passage of the plurality of inlet passages 852a and the plurality of outlet passages 852b being separated from each of at least one adjacent passage by a passage wall 856.
  • the flow field plate 826 may be considered to be configured as an interdigitated flow field configuration (however, it will be appreciated that the flow field plate 826 may be configured as an alternative flow field configuration, such as a partially interdigitated flow field configuration or a serpentine flow field configuration).
  • the plurality of inlet passages 852a may extend along a positive direction of the x-axis
  • the plurality of outlet passages 852b may extend along a negative direction of the x- axis, each passage of the plurality of inlet passages 852a and the plurality of outlet passages 852b terminating at an end wall 854.
  • each passage of the plurality of inlet passages 852a and the plurality of outlet passages 852b may have a uniform height 858 and a uniform thickness 860. Additionally or alternatively, each passage wall 856 may have the height 858 and a uniform thickness 862. In some examples, the height 858 may be between 1 mm and 5 mm, the thickness 860 may be between 1 mm and 5 mm, and the thickness 862 may be between 1 mm and 4 mm.
  • the flow field plate 826 may be integrally formed in the electrode assembly 802 opposite to a surface 868 of the plate 804 with respect to the z-axis, the surface 868 including a sequential stacking of a carbon foam, a positive electrode, and a negative electrode (not shown at FIGS. 8A-8D) thereon.
  • the electrode assembly 802 may further be included in a stack of electrode assemblies 802 of like configuration.
  • a given electrode assembly 802 may be aligned with other electrode assemblies 802 such that the flow field plate 826 of the given electrode assembly 802 may be in face-sharing contact with a negative electrode of an adjacent electrode assembly 802 and such that the hydrogen gas inlet channel sections 818a of the stack of electrode assemblies 802 may form a continuous hydrogen inlet channel (not shown at FIGS. 8A-8D) fluidically coupled to the plurality of inlet passages 852a of each flow field plate 826 of the stack of electrode assemblies 802. Accordingly, when the H 2 gas flows through the hydrogen gas inlet channel, the plurality of inlet passages 852a of the flow field plate 826 of the given electrode assembly 802 may forcibly convect the H2 gas therethrough and across the negative electrode of the adjacent electrode assembly 802.
  • the hydrogen gas outlet channel sections 818b of the stack of electrode assemblies 802 may form a continuous hydrogen outlet channel (not shown at FIGS.8A-8D) fluidically coupled to the plurality of outlet passages 852b of each flow field plate 826 of the stack of electrode assemblies 802.
  • the plate 804 may further include one or more features to assist in distributing an electrolyte across the surface 868 and through the carbon foam (not shown at FIG.8D) positioned on the surface 868.
  • the plate 804 may include an electrolyte inlet well 812 in which the electrolyte may collect upon flowing to the electrode assembly 802 [e.g., via an electrolyte inlet channel (not shown at FIG. 8D)].
  • the plate 804 may include a berm 814b against which the electrolyte may collect, the berm 814b extending parallel to the x-axis.
  • the berm 814b may include a plurality of electrolyte inlet passages (not shown) set therein and distributed thereacross for allowing the electrolyte to flow through the berm 814b in a positive direction of the y-axis.
  • the plate 804 may include an electrolyte trough 864, which may collect and distribute the electrolyte flowing from the electrolyte inlet well 812 and through the berm 814b via the plurality of electrolyte inlet passages.
  • the plate 804 may be tilted with respect to a direction of gravity, such that the electrolyte may be gravity fed along the positive direction of the y-axis and through the plurality of electrolyte inlet passages.
  • the z-axis may either be aligned with or offset from a vertical direction opposite to the direction of gravity at an angle of 0° to 30°.
  • the electrolyte from the electrolyte inlet well 812 may be substantially evenly distributed across the surface 868 (e.g., through the carbon foam of the electrode assembly 802).
  • the carbon foam 306 of FIGS.3-4B, 6A, and 6B or the carbon foam 706 of FIGS.7A and 7B may be replaced with a flow field plate of substantially similar flow field configuration to the flow field plate 826.
  • the flow field configuration of the flow field plate replacing the carbon foam 306 or the carbon foam 706 may be oriented in the same direction as the flow field configuration of the flow field plate 826 with respect to the x- and y-axes.
  • the flow field configuration of the flow field plate replacing the carbon foam 306 or the carbon foam 706 may be oriented in a different direction as the flow field configuration of the flow field plate 826 (e.g., at a 90° angle, a 180° angle, or a 270° angle) with respect to the x- and y-axes.
  • FIGS. 9A and 9B perspective views 900 and 950 are respectively shown, each of perspective views 900 and 950 depicting the sloped support 220 of the rebalancing cell 202.
  • an upper surface 902 of the sloped support 220 may be parallel to, or offset from, each of a lower surface 904, a back foot 906, and a front foot 908 of the sloped support 220 at the angle 222.
  • the angle 222 may range from 0° to 30°.
  • a height 910 between the back foot 906 and the upper surface 902 and a height 912 between the front foot 908 and the upper surface 902 may be the same, or may differ, depending on the angle 222.
  • the height 910 may be equal to the height 912.
  • the height 910 may be greater than the height 912.
  • the sloped support 220 may be formed from a relatively lightweight material.
  • the sloped support 220 may be formed from a non-corrosive material with relatively high strength-to-weight ratio and impact strength and relatively low friction.
  • the sloped support 220 may be formed from high-density polyethylene (HDPE).
  • the sloped support 220 may be adjustable in that the angle 222 may be adjusted to level the cell enclosure of the rebalancing cell (not shown at FIGS.9A and 9B) with respect to a direction of gravity.
  • the sloped support 220 may be removably coupled (e.g., removably fastened) to the cell enclosure such that other supports may be substituted to raise or lower than angle 222.
  • an adjusting mechanism e.g., a hinge, reversible locking elements, etc.; not shown at FIGS.9A and 9B
  • FIG.10 an example plot 1000 depicting an Fe 3+ reduction rate as a function of a total concentration of Fe 3+ reduced in exemplary rebalancing cells is shown.
  • Each of the rebalancing cells are independently included in all-iron hybrid redox flow battery systems of like configuration.
  • an abscissa represents the total amount of Fe 3+ reduced (in mol/m 2 ) and an ordinate represents the Fe 3+ reduction rate (in mol/m 2 hr).
  • curves 1002, 1004, and 1006 represent the Fe 3+ reduction rates for the various rebalancing cells.
  • curve 1002 represents an average Fe 3+ reduction rate for a typical jelly roll rebalancing reactor
  • curve 1004 represents an average Fe 3+ reduction rate for a first exemplary rebalancing cell
  • curve 1006 represents an average Fe 3+ reduction rate for a second exemplary rebalancing cell.
  • Each of the first and second exemplary rebalancing cells include a stack of internally shorted electrode assemblies through which H 2 gas flows via convection and electrolyte flows via gravity feeding and capillary action.
  • Each of the internally shorted electrode assemblies of the first and second exemplary rebalancing cells may include a sequential stacking of a carbon foam, a positive electrode, and a negative electrode.
  • the negative electrodes of the first exemplary rebalancing cell include a Nafion TM binder
  • the negative electrodes of the second exemplary rebalancing cell include a PTFE binder.
  • the average Fe 3+ reduction rate may initially be ⁇ 60 mol/m 2 hr (as indicated by curve 1004) and for the second exemplary rebalancing cell, the Fe 3+ reduction rate may remain at or above 50 mol/m 2 hr (as indicated by curve 1006).
  • the average Fe 3 reduction rate for the first exemplary rebalancing cell may deteriorate during extended use (as measured by the total amount of Fe 3+ reduced).
  • the average Fe 3+ reduction rate of the first exemplary rebalancing cell may deteriorate to less than 20 mol/m 2 hr after about 3000 mol/m 2 total Fe 3+ is reduced (as indicated by curve 1004).
  • the second exemplary rebalancing cell is shown to maintain Fe 3+ reduction performance beyond 16000 mol/m 2 total Fe 3+ reduced.
  • FIG.11 a flow chart of a method 1100 for operating a rebalancing cell including a stack of internally shorted electrode assemblies (e.g., wherein electric current flowing through the stack of internally shorted electrode assemblies is not channeled through an external load) is shown.
  • the rebalancing cell may be implemented in a redox flow battery system for decreasing excess H2 gas and rebalancing charge imbalances in an electrolyte therein.
  • the redox flow battery system may be the redox flow battery system 10 of FIG.1 and the rebalancing cell may be the rebalancing cell 202 of FIGS.2A and 2B.
  • method 1100 may be considered with reference to the embodiments of FIGS.1-2B, alone or in combination with the embodiments and considerations of FIGS.3-9B (though it may be understood that similar methods may be applied to other systems without departing from the scope of the present disclosure).
  • steps or portions of steps e.g., involving receiving the H2 gas and the electrolyte for distribution at the rebalancing cell
  • steps may be carried out via the controller 88 of FIG.1, and may be stored as executable instructions at a non-transitory storage medium (e.g., memory) communicably coupled to the controller 88.
  • a non-transitory storage medium e.g., memory
  • method 1100 includes receiving the H 2 gas and the electrolyte at the rebalancing cell via respective inlet ports thereof. Specifically, the electrolyte may be received at the rebalancing cell via a first inlet port and the H2 gas may be received at the rebalancing cell via a second inlet port. In one example, the first inlet port being positioned above the second inlet port with respect to a direction of gravity. [0146] At 1104, method 1100 includes distributing the H2 gas and the electrolyte throughout the stack of internally shorted electrode assemblies.
  • the electrolyte may be distributed via an inlet manifold including a plurality of first inlet channels respectively coupled to the electrode assemblies of the stack of internally shorted electrode assemblies and the H2 gas may be distributed via a second inlet channel formed by the stack of internally shorted electrode assemblies and fluidically coupled to each electrode assembly of the stack of internally shorted electrode assemblies.
  • the electrolyte may be distributed through first flow field plates respectively interfacing with positive electrodes of the stack of internally shorted electrode assemblies.
  • the electrolyte may be distributed through activated carbon foams respectively interfacing with the positive electrodes.
  • the H2 gas may be distributed through second flow field plates respectively interfacing with negative electrodes of the stack of internally shorted electrode assemblies.
  • method 1100 includes inducing flows (e.g., crosswise, parallel, or opposing flows) of the H2 gas and the electrolyte to perform an electrolyte rebalancing reaction at the negative and positive electrodes of the stack of internally shorted electrode assemblies.
  • the negative and positive electrodes may be distributed among the stack of internally shorted electrode assemblies in interfacing pairs of negative and positive electrodes. As discussed above, each positive electrode of the interfacing pairs of negative and positive electrodes may further interface with a respective activated carbon foam or a respective first flow field plate.
  • the negative electrode may be a conductive carbon substrate having a Pt catalyst coated thereon and the positive electrode may be a carbon felt.
  • inducing flows of the H2 gas and the electrolyte may include: (i) at 1108, inducing flow of the H2 gas across the negative electrodes of the stack of internally shorted electrode assemblies via convection (e.g., forced convection via the second flow field plates interfacing with the negative electrodes of the stack of internally shorted electrode assemblies); and (ii) at 1110, inducing flow of the electrolyte across the positive electrodes of the stack of internally shorted electrode assemblies via one or more of gravity feeding (e.g., by tilting the rebalancing cell relative to a direction of gravity), capillary action (e.g., wicking up the electrolyte into the positive electrodes of the stack of internally shorted electrode assemblies), and convection (e.g., forced convection via the first flow field plates interfacing with the positive electrodes of the stack of
  • the flow of H2 gas may be induced across the negative electrodes by convection and the flow of the electrolyte may be induced across the positive electrodes by each of gravity feeding and capillary action.
  • the electrolyte rebalancing reaction may be performed, including, at 1112, reacting the H2 gas with positively charged ions in the electrolyte to reduce the positively charged ions (see equation (4)).
  • method 1100 includes expelling the electrolyte (having the reduced positively charged ions, e.g., a lower concentration of Fe 3+ than upon being received at the first inlet port at 1102) and any unreacted H 2 gas from the rebalancing cell via outlet ports thereof.
  • the electrolyte may be expelled from the rebalancing cell via a first outlet port and, in some examples, at 1118, the unreacted H2 gas may be expelled from the rebalancing cell via a second outlet port.
  • the rebalancing cell may include a dead ended configuration for flowing the H 2 gas and no second outlet port may be included.
  • expelling the unreacted H2 gas from the rebalancing cell may include, at 1120, expelling the unreacted H 2 gas in the electrolyte via a pressure release outlet port (e.g., to prevent pressure from building up in the electrolyte and flooding the negative electrodes of the stack of internally shorted electrode assemblies).
  • a pressure release outlet port e.g., to prevent pressure from building up in the electrolyte and flooding the negative electrodes of the stack of internally shorted electrode assemblies.
  • flows of H 2 gas and a charge- imbalanced electrolyte from the redox flow battery may be provided to the rebalancing cell and induced across negative and positive electrodes of the stack of internally shorted electrode assemblies.
  • the H 2 gas may be convected across the negative electrodes via a flow field plate.
  • the charge-imbalanced electrolyte may be gravity fed and/or convected through the stack of internally shorted electrode assemblies and wicked into the positive electrodes therein.
  • the negative and positive electrodes may be electrically conductive and in face-sharing contact with one another, such that electric current may not be directed away from the rebalancing cell (e.g., through an external load).
  • each electrode assembly of the stack of internally shorted electrode assemblies is internally electrically shorted and electrically decoupled from each other electrode assembly of the stack of internally shorted electrode assemblies, reverse electric current may be prevented from flowing across the entire stack of internally shorted electrode assemblies when one electrode assembly is degraded (e.g., experiences a spike in the electric current).
  • internal electrical shorting increased electrolyte rebalancing rates without sacrificing an overall reliability of the rebalancing cell.
  • a rebalancing cell for a redox flow battery comprising: a cell enclosure; a hydrogen gas inlet port through which H 2 gas is flowed into the cell enclosure; an electrolyte inlet port through which an electrolyte is flowed into the cell enclosure; an electrolyte outlet port through which the electrolyte is expelled from the cell enclosure; a stack of electrode assemblies enclosed by the cell enclosure, each electrode assembly of the stack of electrode assemblies including a negative electrode in face-sharing contact with a flow field plate; and a sloped support coupled to the cell enclosure.
  • a first example of the rebalancing cell further includes wherein the electrolyte outlet port is positioned lower than the electrolyte inlet port with respect to a direction of gravity.
  • a second example of the rebalancing cell optionally including the first example of the rebalancing cell, further comprises a pressure release outlet port for expelling unreacted H2 gas from the electrolyte.
  • a third example of the rebalancing cell optionally including one or more of the first and second examples of the rebalancing cell, wherein the unreacted H 2 gas is only expelled from the cell enclosure after flowing through the negative electrodes of the stack of electrode assemblies into the electrolyte and through the pressure release outlet port.
  • a fourth example of the rebalancing cell optionally including one or more of the first through third examples of the rebalancing cell, further comprises a hydrogen gas outlet port through which unreacted H2 gas is expelled from the cell enclosure.
  • a fifth example of the rebalancing cell optionally including one or more of the first through fourth examples of the rebalancing cell, further includes wherein the hydrogen gas inlet port, the hydrogen gas outlet port, the electrolyte inlet port, and the electrolyte outlet port are positioned on the cell enclosure in a crosswise configuration, the crosswise configuration including the hydrogen gas outlet port and the electrolyte inlet port being positioned on different sides of an upper half of the cell enclosure and the hydrogen gas inlet port and the electrolyte outlet port being positioned on different sides of a lower half of the cell enclosure.
  • a sixth example of the rebalancing cell optionally including one or more of the first through fifth examples of the rebalancing cell, further includes wherein the H 2 gas is directed from the hydrogen gas inlet port to one or more hydrogen gas inlet passages respectively formed from the flow field plates in face-sharing contact with the negative electrodes of the stack of electrode assemblies.
  • a seventh example of the rebalancing cell optionally including one or more of the first through sixth examples of the rebalancing cell, further includes wherein each electrode assembly of the stack of electrode assemblies is internally shorted and no electric current is directed away from the rebalancing cell.
  • An eighth example of the rebalancing cell optionally including one or more of the first through seventh examples of the rebalancing cell, further includes wherein the sloped support tilts the cell enclosure with respect to an external surface on which the sloped support rests at an angle between 2° and 30°.
  • a ninth example of the rebalancing cell optionally including one or more of the first through eighth examples of the rebalancing cell, further includes wherein each negative electrode of the stack of electrode assemblies is formed from a conductive carbon substrate with a catalyst coated thereon, where the catalyst comprises a precious metal catalyst comprising Pd, Rh, Ru, Ir, Ta, or alloys thereof; or a non-precious metal catalyst stable in ferric solution.
  • a tenth example of the rebalancing cell optionally including one or more of the first through ninth examples of the rebalancing cell, further includes wherein the flow field plates in face-sharing contact with the negative electrodes of the stack of electrode assemblies are configured as interdigitated flow field configurations, partially interdigitated flow field configurations, serpentine flow field configurations, or a combination thereof.
  • An eleventh example of the rebalancing cell optionally including one or more of the first through tenth examples of the rebalancing cell, further includes wherein each negative electrode of the stack of electrode assemblies is further in face-sharing contact with a positive electrode formed from a wicking conductive carbon felt optionally in face-sharing contact with a carbon foam.
  • a twelfth example of the rebalancing cell optionally including one or more of the first through eleventh examples of the rebalancing cell, further includes wherein the electrolyte is directed from the electrolyte inlet port through the carbon foams of the stack of electrode assemblies to the electrolyte outlet port.
  • a thirteenth example of the rebalancing cell optionally including one or more of the first through twelfth examples of the rebalancing cell, further includes wherein each electrode assembly of the stack of electrode assemblies further comprises a plurality of electrolyte inlet passages positioned adjacent to the carbon foam for distributing the electrolyte received at the electrolyte inlet port across the carbon foam.
  • a redox flow battery system comprising: positive and negative electrode compartments respectively housing redox and plating electrodes; positive and negative electrolyte chambers respectively including a positive electrolyte for pumping to the positive electrode compartment and a negative electrolyte for pumping to the negative electrode compartment, where the positive and negative electrolyte chambers further include respective gas head spaces; and a first rebalancing cell for electrolyte rebalancing of the positive electrolyte, the first rebalancing cell being fluidically coupled to the positive electrode compartment and the gas head space of the positive electrolyte chamber, wherein the electrolyte rebalancing of the positive electrolyte is driven via internal electrical shorting of interfacing pairs of positive and negative electrodes of the first rebalancing cell, H 2 gas being convected through the first rebalancing cell via a first flow field configuration, and the positive electrolyte being directed through the first rebalancing cell via gravity feeding and capillary action.
  • a first example of the redox flow battery system further includes wherein the H 2 gas flows into the first rebalancing cell from the gas head space of the positive electrolyte chamber, and the positive electrolyte flows into the first rebalancing cell from the positive electrode compartment.
  • a second example of the redox flow battery system optionally including the first example of the redox flow battery system, further includes wherein, for each of the interfacing pairs of the first rebalancing cell, the positive and negative electrodes are in face-sharing contact with one another and are continuously electrically conductive.
  • a third example of the redox flow battery system optionally including one or more of the first and second examples of the redox flow battery system, further includes wherein the redox flow battery system is an all-iron hybrid redox flow battery system, and wherein the electrolyte rebalancing of the positive electrolyte includes reducing Fe 3+ in the positive electrolyte to Fe 2+ .
  • a fourth example of the redox flow battery system optionally including one or more of the first through third examples of the redox flow battery system, further comprises a second rebalancing cell for electrolyte rebalancing of the negative electrolyte, the second rebalancing cell being fluidically coupled to the negative electrode compartment and the gas head space of the negative electrolyte chamber, wherein the electrolyte rebalancing of the negative electrolyte is driven via internal electrical shorting of interfacing pairs of positive and negative electrodes of the second rebalancing cell, H 2 gas being convected through the second rebalancing cell via a second flow field configuration, and the negative electrolyte being directed through the second rebalancing cell via gravity feeding and capillary action.
  • a method for a redox flow battery system comprising: receiving H 2 gas and an electrolyte at respective inlet ports of a rebalancing cell of the redox flow battery system; distributing the H2 gas and the electrolyte throughout an electrode assembly stack of the rebalancing cell; and inducing flow of the H2 gas across anodes of the electrode assembly stack via convection; and thereafter reacting the H 2 gas with positively charged ions in the electrolyte to reduce the positively charged ions; and expelling unreacted H2 gas and the electrolyte from the rebalancing cell via outlet ports thereof.
  • a first example of the method further comprises inducing flow of the electrolyte across cathodes of the electrode assembly stack via gravity feeding and capillary action prior to reacting the H 2 gas with the positively charged ions.
  • a second example of the method optionally including the first example of the method, further includes wherein the H2 gas is reacted with the positively charged ions via an electrolyte rebalancing reaction at respective interfaces of the cathodes of the electrode assembly stack with the anodes of the electrode assembly stack.
  • a third example of the method optionally including one or more of the first and second examples of the method, further includes wherein electric current flowing through the electrode assembly stack is not channeled through an external load.
  • an electrode assembly stack for a redox flow battery cell comprising: a plurality of internally shorted electrode assemblies, each of the plurality of internally shorted electrode assemblies comprising: a positive electrode formed from a wicking carbon felt; and an electrolyte flow field plate in face-sharing contact with the positive electrode, where passages of the electrolyte flow field plate are fluidically coupled to the redox flow battery cell.
  • a first example of the electrode assembly stack further includes wherein each of the plurality of internally shorted electrode assemblies further comprises: a hydrogen gas flow field plate, where passages of the hydrogen gas flow field plate are fluidically coupled to the redox flow battery cell; and a negative electrode positioned between the hydrogen gas flow field plate and the positive electrode and in face-sharing contact with each of the hydrogen gas flow field plate and the positive electrode, the negative electrode being on a side of the positive electrode opposite from the electrolyte flow field plate.
  • a second example of the electrode assembly stack further includes wherein the passages of the electrolyte flow field plate of each of the plurality of internally shorted electrode assemblies are fluidically coupled to a positive electrode compartment of the redox flow battery cell, optionally wherein the passages of the hydrogen gas flow field plate of each of the plurality of internally shorted electrode assemblies are fluidically coupled to a gas head space of a positive electrolyte chamber fluidically coupled to the redox flow battery cell.
  • a third example of the electrode assembly stack optionally including one or more of the first and second examples of the electrode assembly stack, further includes wherein the passages of the electrolyte flow field plate of each of the plurality of internally shorted electrode assemblies are fluidically coupled to a negative electrode compartment of the redox flow battery cell, optionally wherein the passages of the hydrogen gas flow field plate of each of the plurality of internally shorted electrode assemblies are fluidically coupled to a gas head space of a negative electrolyte chamber fluidically coupled to the redox flow battery cell.
  • a fourth example of the electrode assembly stack optionally including one or more of the first through third examples of the electrode assembly stack, further includes wherein the passages of the electrolyte flow field plate of each of the plurality of internally shorted electrode assemblies form at least a portion of an electrolyte flow path through the electrode assembly stack, optionally wherein the passages of the hydrogen gas flow field plate of each of the plurality of internally shorted electrode assemblies form at least a portion of a hydrogen gas flow path through the electrode assembly stack.
  • a fifth example of the electrode assembly stack optionally including one or more of the first through fourth examples of the electrode assembly stack, further includes wherein the electrode assembly stack is tilted with respect to gravity.
  • a rebalancing cell for a redox flow battery comprising: a cell enclosure; an electrolyte inlet port through which an electrolyte is flowed into the cell enclosure; an electrolyte outlet port through which the electrolyte is expelled from the cell enclosure; a stack of electrode assemblies enclosed by the cell enclosure, each electrode assembly of the stack of electrode assemblies including a positive electrode formed from a wicking conductive carbon felt; and a sloped support coupled to the cell enclosure, where the sloped support tilts the cell enclosure with respect to an external surface on which the sloped support rests.
  • a first example of the rebalancing cell further includes wherein each positive electrode of the stack of electrode assemblies is in face-sharing contact with a carbon foam.
  • a second example of the rebalancing cell optionally including the first example of the rebalancing cell, further includes wherein the electrolyte is directed from the electrolyte inlet port to the electrolyte outlet port via each of an electrolyte inlet manifold and the carbon foams of the stack of electrode assemblies.
  • a third example of the rebalancing cell optionally including one or more of the first and second examples of the rebalancing cell, further includes wherein each electrode assembly of the stack of electrode assemblies further comprises a plurality of electrolyte inlet passages positioned adjacent to the carbon foam for distributing the electrolyte received at the electrolyte inlet port across the carbon foam.
  • a fourth example of the rebalancing cell optionally including one or more of the first through third examples of the rebalancing cell, further includes wherein each positive electrode of the stack of electrode assemblies is in face-sharing contact with a flow field plate.
  • a fifth example of the rebalancing cell optionally including one or more of the first through fourth examples of the rebalancing cell, further includes wherein the electrolyte is directed from the electrolyte inlet port to the electrolyte outlet port via each of an electrolyte inlet manifold and the flow field plates in face-sharing contact with the positive electrodes of the stack of electrode assemblies.
  • a sixth example of the rebalancing cell optionally including one or more of the first through fifth examples of the rebalancing cell, further includes wherein the flow field plates in face-sharing contact with the positive electrodes of the stack of electrode assemblies are configured as interdigitated flow field configurations, partially interdigitated flow field configurations, serpentine flow field configurations, or a combination thereof.
  • a seventh example of the rebalancing cell optionally including one or more of the first through sixth examples of the rebalancing cell, further includes wherein each positive electrode of the stack of electrode assemblies is in face-sharing contact with a negative electrode, and wherein the positive and negative electrodes within each electrode assembly of the stack of electrode assemblies are continuously electrically conductive.
  • An eighth example of the rebalancing cell optionally including one or more of the first through seventh examples of the rebalancing cell, further includes wherein the sloped support tilts the cell enclosure with respect to the external surface on which the sloped support rests at an angle between 2° and 30°.
  • a method for a redox flow battery system comprising: receiving an electrolyte at an inlet port of a rebalancing cell of the redox flow battery system; distributing the electrolyte throughout an electrode assembly stack of the rebalancing cell; inducing flow of the electrolyte across cathodes of the electrode assembly stack via one or more of gravity feeding, capillary action, and convection; reducing positively charged ions in the electrolyte via an electrolyte rebalancing reaction at respective interfaces of the cathodes of the electrode assembly stack with anodes of the electrode assembly stack; and expelling the electrolyte from the rebalancing cell via an outlet port thereof.
  • a first example of the method further includes wherein each cathode of the electrode assembly stack interfaces with an activated carbon foam, and wherein distributing the electrolyte throughout the electrode assembly stack comprises distributing the electrolyte through the activated carbon foams respectively interfacing with the cathodes of the electrode assembly stack.
  • a second example of the method optionally including the first example of the method, further includes wherein each cathode of the electrode assembly stack interfaces with a flow field plate, wherein distributing the electrolyte throughout the electrode assembly stack comprises distributing the electrolyte through the flow field plates respectively interfacing with the cathodes of the electrode assembly stack, and wherein the flow of the electrolyte is induced at least via convection forced by the flow field plate.
  • a third example of the method optionally including one or more of the first and second examples of the method, further includes wherein each cathode of the electrode assembly stack is a carbon felt, and wherein the flow of the electrolyte is induced at least via capillary action of the carbon felt.
  • a fourth example of the method optionally including one or more of the first through third examples of the method, further includes wherein the rebalancing cell is tilted with respect to a surface on which the rebalancing cell rests, and wherein the flow of the electrolyte is induced at least via gravity feeding.
  • a fifth example of the method optionally including one or more of the first through fourth examples of the method, further includes wherein the electrolyte has a greater concentration of Fe 3+ upon being received at the inlet port than upon being expelled via the outlet port.
  • FIGS.2A-4B and 6A-9B show example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact.
  • elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example.
  • elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another.
  • a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example.
  • top/bottom, upper/lower, above/below may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another.
  • FIGS.2A-4B and 6A-9B are drawn approximately to scale, although other dimensions or relative dimensions may be used.

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Abstract

La présente invention concerne des systèmes et des procédés pour une cellule de rééquilibrage de batterie à flux redox. Dans un exemple, la cellule de rééquilibrage peut comprendre une pile d'ensembles électrodes, chaque ensemble électrode pouvant comprendre une électrode négative en interface avec une plaque de champ d'écoulement pour induire un écoulement de gaz H2 à partir de la batterie à flux redox. Dans certains exemples, chaque ensemble électrode peut en outre comprendre une électrode positive constituée d'un feutre de carbone à effet de mèche pour induire l'écoulement d'un électrolyte à partir de la batterie à flux redox. Dans certains exemples, aucun courant électrique ne peut être dirigé hors de la cellule de rééquilibrage et les électrodes négatives et positives de chaque ensemble électrode peuvent être électriquement conductrices en continu. De cette manière, chaque ensemble électrode de la cellule de rééquilibrage peut être en court-circuit interne, augmentant ainsi les taux de réduction de la cellule de rééquilibrage sans sacrifier la fiabilité globale.
EP22843035.1A 2021-07-13 2022-07-13 Cellule de rééquilibrage pour système de batterie à flux redox Pending EP4348742A1 (fr)

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CN101257121B (zh) * 2007-03-02 2012-08-22 新南创新私人有限公司 用于钒液流电池组的电极和电解液的制备方法以及再平衡方法
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US10230125B2 (en) * 2014-03-06 2019-03-12 Ess Tech, Inc. Method and system to maintain electrolyte stability for all-iron redox flow batteries
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US10109879B2 (en) * 2016-05-27 2018-10-23 Lockheed Martin Energy, Llc Flow batteries having an electrode with a density gradient and methods for production and use thereof
US11817606B2 (en) * 2017-04-28 2023-11-14 Ess Tech, Inc. Methods and systems for rebalancing electrolytes for a redox flow battery system
AU2018350796B2 (en) * 2017-10-20 2024-02-29 Lockheed Martin Energy, Llc pH buffering region in a flow battery rebalancing cell
EP3641041A1 (fr) * 2018-10-16 2020-04-22 LANXESS Deutschland GmbH Électrode de carbone pour des batteries à flux redox bichromate
CN209860061U (zh) * 2019-05-22 2019-12-27 江明珍 一种用于液流电池容量恢复的再平衡电池

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