WO2022173785A1 - Batteries à flux redox aqueuse comprenant des additifs solides à activité redox - Google Patents

Batteries à flux redox aqueuse comprenant des additifs solides à activité redox Download PDF

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Publication number
WO2022173785A1
WO2022173785A1 PCT/US2022/015749 US2022015749W WO2022173785A1 WO 2022173785 A1 WO2022173785 A1 WO 2022173785A1 US 2022015749 W US2022015749 W US 2022015749W WO 2022173785 A1 WO2022173785 A1 WO 2022173785A1
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redox
aqueous
flow battery
redox flow
active additive
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PCT/US2022/015749
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English (en)
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Daniel R. Gamelin
Jose J. ARAUJO
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University Of Washington
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    • 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

Definitions

  • an aqueous redox flow battery includes an aqueous electrolyte comprising a redox-active additive and a redox mediator.
  • the redox-active additive can increase an energy storage capacity of the aqueous redox flow battery by at least 10%, compared to the energy storage capacity of an aqueous redox flow battery without the redox-active additive in the aqueous electrolyte.
  • the redox-active additive can be or include a redox-active solid.
  • the redox-active additive can be or include titanium (Ti), lead (Pb), iron (Fe), zinc (Zn), tin (Sn), copper (Cu), nickel (Ni), cobalt (Co), bismuth (Bi), sodium (Na), lithium (Li), magnesium (Mg), compounds thereof, oxides thereof, complexes thereof, salts thereof, or any combination thereof.
  • the redox-active additive can be or include Ti, Zn, Li, compounds thereof, oxides thereof, complexes thereof, salts thereof, or any combination thereof.
  • the redox-active additive can be or include a redox- active metal.
  • the redox-active additive can be or include zinc metal.
  • the zinc metal can be in the form of a powder, mossy zinc, zinc mesh, electrodepo sited zinc, zinc foam, zinc pellets or any combination thereof.
  • the redox-active additive can be in the form of a powder.
  • the redox-active additive can be insoluble in at least one of a reduced form or an oxidized form in the aqueous electrolyte.
  • the water-soluble redox mediator can have a redox potential within about +/- 200 mV of the redox potential of the redox-active additive.
  • the redox mediator can be water-soluble.
  • the redox mediator can be or include a water- soluble aqueous transition metal-containing redox mediator.
  • the redox mediator can be or include a transition metal coordination compound optionally comprising a ligand selected from triethanolamine, triisopropanolamine, bipyridine, porphyrins, bridging oxides, and any derivatives thereof.
  • the redox mediator can be or include a water-soluble organometallic compound.
  • the redox mediator can be or include an aqueous organoiron compound.
  • the redox mediator can be selected from [Fe(TEOA)OH] 1_/2 , [EcfPPAjOHJ l _/2 ⁇ and any combination thereof.
  • the redox mediator can be dissolved in the negative electrolyte electrolyte and/or the positive electrolyte.
  • the electrolyte(s) can be or include the redox mediatonredox-active additive at a molar ratio of from 1:0.1 to 1:25.
  • the aqueous redox flow battery can comprise a volumetric power density of from 5 Wh/L to 200 Wh/L.
  • the aqueous redox flow battery can be substantially free of dendrites formed from the redox-active additive.
  • an aqueous redox flow battery includes a negative electrolyte tank.
  • the negative electrolyte tank can include an aqueous electrolyte including a redox-active additive and a water-soluble redox mediator of the preceding aspect.
  • the aqueous redox flow battery can include a negative electrode in fluid communication with the negative electrolyte tank.
  • the aqueous redox flow battery can include a positive electrolyte tank comprising a positive electrolyte.
  • the aqueous redox flow battery can include a positive electrode in fluid communication with the positive electrolyte tank.
  • the aqueous redox flow battery can include an ion-permeable separator between the negative electrode and the positive electrode.
  • a method of operating a redox flow battery of the preceding aspect includes charging the aqueous redox flow battery by drawing a current density from 10 mA/cm 2 to 400 mA/cm 2 at a voltage from 0.5 V to 1.8 V from the aqueous redox flow battery.
  • FIG. 1 is a schematic diagram illustrating a redox flow battery with electron transport in the circuit, ion transport in the electrolyte and across the membrane, active species crossover, and mass transport in the electrolyte, in accordance with embodiments of the present disclosure.
  • FIG. 2A is a schematic diagram illustrating an all-slurry flow redox battery, in accordance with embodiments of the present disclosure.
  • FIG. 2B is a schematic diagram illustrating a metal/slurry flow redox battery., in accordance with embodiments of the present disclosure.
  • FIG. 3 is a schematic diagram illustrating a redox-targeting flow battery., in accordance with embodiments of the present disclosure.
  • FIG. 4 is a block flow diagram of an example process 400 for operating an aqueous RFB configured as described above, in accordance with embodiments of the present disclosure.
  • FIG. 5 is a graph of example cyclic voltammograms of [Fe(TEOA)OH] 2 and [Fe(CN) 6 ] 3 , in accordance with embodiments of the present disclosure.
  • the [Fe(TEOA)OH] 2 solution contained 0.5 M FeCh ⁇ FbO and 1.0 M TEOA. The pH was adjusted to 13.96 with 10.2 equivalents of NaOH. The current was multiplied by 3 for clarity.
  • the discharged solution was prepared by electrochemical oxidation.
  • FIG. 7A is a graph of example absorption spectra of 0.1 M [Fe(TEOA)OH] after additions of Zn powder, in accordance with embodiments of the present disclosure.
  • the graph was prepared from solutions for which a total of 13.5 mg Zn powder (0.6 equivalents) was added in 3 approximately equal portions.
  • FIG. 7B is a graph of example absorption spectra of 0.1 M [Fe(TEOA)OH] 2 after additions of ZnO powder, in accordance with embodiments of the present disclosure.
  • the graph was prepared from solutions for which a total of 34.6 mg ZnO powder (-0.8 equivalents) was added in 6 approximately equal portions.
  • FIG. 8 is a graph of example redox flow battery cell potential data for five charge/discharge cycles at 40 mA cm 2 , in accordance with embodiments of the present disclosure. Voltage limits were set to define the range 1.6 - 0.5 V.
  • the catholyte was 1.0 M [Fe(CN) 6 ] 3 in 0.5 M NaOH solution (pH 13.97).
  • the anolyte was 0.5 M [Fe(TEOA)OH] 2 in NaOH solution (pH -13.9) with a 2: 1 TEOA:Fe stoichiometry.
  • FIG. 9A is a graph of example cell potential (V) data as a function of capacity (mAh) for two full redox flow battery charge/discharge cycles, in accordance with embodiments of the present disclosure.
  • the voltage limits were set between 1.6 - 0.5 V with an 80 mA cm 2 current density.
  • the catholyte was 1.0 M [Fe(CN) 6 ] 3 in 0.5 M NaOH solution (pH 13.97).
  • the anolyte was 0.5 M [Fe(TEOA)OH] 2 in NaOH solution (pH -13.9) with a 2:1 TEOA:Fe stoichiometric excess.
  • FIG. 9B is a graph of example capacity (mAh, left ordinate) and relative change in capacity (%, right ordinate) plotted as a function of the equivalents of Zn powder added to the data in FIG. 9A, in accordance with embodiments of the present disclosure.
  • charge capacity is indicated by squares and discharge capacity is indicated by triangles.
  • FIG. 10A is a graph of example discharge capacity (mAh, left ordinate) and discharge efficiency (%, right ordinate) data as a function of cycle number for a full redox flow battery, in accordance with embodiments of the present disclosure.
  • the catholyte was 1.0 M K3[Fe(CN)6] in 1.0 M NaOH.
  • the anolyte was 0.4 M [Fe(TEOA)OH] 2 in 4.0 M NaOH with a 2.5:1 TEOA:Fe ratio and varying amounts of added Zn.
  • Voltage limits were set between 1.6 - 0.5 V with a 40 mA cm 2 current density.
  • FIG. 10B is a graph of example discharge capacity (mAh, left ordinate) and discharge efficiency (%, right ordinate) data as a function of cycle number for a full redox flow battery, in accordance with embodiments of the present disclosure.
  • the catholyte was 1.0 M K3[Fe(CN)6] in 1.0 M NaOH.
  • the anolyte was 0.4 M [Fe(TEOA)OH] 2 in 4.0 M NaOH with a 4: 1 TEOA:Fe ratio and varying amounts of added Zn.
  • Voltage limits were set between 1.6 - 0.5 V with a 40 mA cm 2 current density
  • FIG. 11 is a graph of cell potential data as a function of time for a redox flow battery for which addition of solid to anolyte increases discharge time, in accordance with embodiments of the present disclosure.
  • FIG. 12A is a greyscale image of a flow cell for a redox flow battery testing station, in accordance with embodiments of the present disclosure.
  • FIG. 12B is a greyscale image of a redox flow battery testing station including a flow loop and controller, in accordance with embodiments of the present disclosure.
  • FIG. 13 is a graph of example cell potential data as a function of capacity for a redox flow battery illustrating the increase of capacity upon addition of additive, in accordance with embodiments of the present disclosure.
  • FIG. 14 is a graph of example cell potential data as a function of capacity for a redox flow battery illustrating the increase of capacity upon addition of additive, in accordance with embodiments of the present disclosure.
  • an “electrochemical cell” is a device capable of either deriving electrical energy from chemical reactions or facilitating chemical reactions through the introduction of electrical energy.
  • An electrochemical cell has two half-cells. Each half cell includes an electrode and an electrolyte. The two half-cells may use the same electrolyte, or they may use different electrolytes. In a full electrochemical cell, species from one half-cell lose electrons (oxidation) to their electrode while species from the other half-cell gain electrons (reduction) from their electrode.
  • a plurality of electrochemical cells electrically connected together in series within a common housing is generally referred to as an electrochemical "stack.”
  • a “redox (reduction/oxidation) flow battery” is a special type of electrochemical system in which an electrolyte containing one or more dissolved electroactive species flows through a plurality of electrochemical cells.
  • a common redox flow battery electrochemical cell configuration includes a positive electrode (also referred to interchangeably as a cathode) and a negative electrode (also referred to interchangeably as an anode) separated by an ion exchange membrane or a separator, and two circulating electrolyte solutions (positive and negative electrolyte flowstreams generally referred to as the "catholyte” and “anolyte,” respectively).
  • the energy conversion between electrical energy and chemical potential occurs instantly at the electrodes once the liquid electrolyte begins to flow through the cells.
  • the term “battery” is used interchangeably with “cell” or “electrochemical cell.”
  • dendrites refers to the needle-like dendritic crystals that form on the surface of an electrode during charging/discharging of a battery.
  • the compounds described herein can be asymmetric ( e.g ., having one or more stereocenters). All stereoisomers, such as enantiomers and diastereomers, are intended unless otherwise indicated.
  • Tautomeric forms result from the swapping of a single bond with an adjacent double bond together with the concomitant migration of a proton.
  • Tautomeric forms include pro to tropic tautomers which are isomeric protonation states having the same empirical formula and total charge.
  • Example prototropic tautomers include ketone - enol pairs, amide - imidic acid pairs, lactam - lactim pairs, amide - imidic acid pairs, enamine - imine pairs, and annular forms where a proton can occupy two or more positions of a heterocyclic system, for example, 1H- and 3H-imidazole, 1H-, 2H- and 4H- 1,2, 4-triazole, 1H- and 2H- isoindole, and 1H- and 2H-pyrazole.
  • Tautomeric forms can be in equilibrium or sterically locked into one form by appropriate substitution.
  • Compounds of the disclosure can also include all isotopes of atoms occurring in the intermediates or final compounds.
  • Isotopes include those atoms having the same atomic number but different mass numbers.
  • isotopes of hydrogen include tritium and deuterium.
  • the compounds of the disclosure, and salts thereof are substantially isolated.
  • substantially isolated is meant that the compound is at least partially or substantially separated from the environment in which it was formed or detected.
  • Partial separation can include, for example, a composition enriched in the compound of the disclosure.
  • Substantial separation can include compositions containing at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, at least about 97%, or at least about 99% by weight of the compound of the disclosure, or salt thereof.
  • an aqueous redox flow battery that is substantially free of dendrites can include one or more dendrites at a quantity and/or density (e.g., dendrites per area) that does not significantly impair the overall performance of the redox flow battery.
  • redox flow batteries represent a viable long-term energy storage solution.
  • FIG. 1 is a schematic diagram illustrating an example redox flow battery 100 with electron transport in the circuit, ion transport in the electrolyte and across a membrane, active species crossover, and mass transport in the electrolyte, in accordance with embodiments of the present disclosure.
  • Example RFB 100 includes a catholyte reservoir 105, an anolyte reservoir 110, holding a catholyte 115 and an anolyte 120, respectively.
  • Electrolytes are fluidically coupled with a flow cell including a cathode 125 and an anode 130 and configured to flow past a conducting surface of the electrodes during charging and discharging. The direction of the arrows in FIG.
  • Electrolytes flow through respective flow channels 135, separated by a separator 140. Electrodes 125-130 are electrically coupled via electronic and/or power circuitry 145.
  • RFBs separate the energy storage and power components.
  • Employing a modular design allows energy storage and power cycling to be decoupled and addressed individually, improving safety relative to sealed lithium-ion batteries.
  • RFBs store energy in liquid electrolytes 115 and 120 that can be held in tanks, which can be scaled up to meet power demands on a megawatt scale.
  • electrolytes 115 and 120 can be pumped through one or more electrochemical cells 150 where redox-active molecules undergo electrochemical reactions at electrodes 125-130.
  • the size and number of electrochemical cells 150 can be scaled up with increasing power demand on a grid-scale (e.g., in a stack).
  • the negative electrolyte 120 yields electrons during discharge cycles.
  • the electrons are collected through external circuit 145 and returned to the electrochemical cell, where they reduce the positive electrolyte 115, referred to herein as a "catholyte.”
  • the process is reversed during charging cycles, where a voltage is applied to the electrochemical cell 150 to recharge the battery. Meanwhile, charge balance is achieved by flow of counter-ions from one electrolyte to the other through a semi-permeable membrane 140.
  • RFBs represent a significant improvement over current grid-scale charge storage technology.
  • Conventional approaches include all-vanadium cells (e.g., electrodes and electrolyte include vanadium). While this approach avoids problems of degradation due to electrolyte crossover, vanadium is costly, rare, and not electrochemically optimized for use in RFB applications.
  • systems described herein improve RFB systems by employing safe, inexpensive, and earth- abundant materials.
  • the electrolyte formulations described herein operate at relatively higher voltages, higher currents, and higher energy densities.
  • One strategy to boost the efficiency of RFBs while keeping their total volume small is to increase electrolyte energy capacity.
  • energy capacity is increased by incorporating redox-active solids into the electrolyte system.
  • Redox-active solids are typically characterized by significantly higher energy densities relative to electrolytes. Therefore, employing redox-active solids in an RFB architecture can increase the energy density of the system without substantially increasing volume of electrolyte to a point where tank size becomes impractical.
  • three system configurations are contemplated: slurry -based, metal/slurry, and redox-targeting RFBs.
  • FIG. 2A is a schematic diagram illustrating an all-slurry flow redox battery 200, in accordance with embodiments of the present disclosure.
  • Slurry -based RFBs contain suspensions of solid redox-active materials 205 and/or conductive solids 210 in supporting electrolyte.
  • the solids 205 directly undergo electrochemical reactions at the electrodes as they are circulated through the cell stack.
  • Slurry-based RFBs take advantage of the higher energy densities of solids, but their complex fluid dynamics and slow reaction kinetics can introduce sigmoidal performance with respect to process parameters such as flowrate, load voltage, operating current, etc.
  • suspended solids 205-210 can settle in tanks 105-110 at relatively low flow/mix rates and can cause erosion and reduced performance due to residence time issues at relatively high flowrates.
  • the techniques described herein with respect to FIG. 3 and Example 1 can improve the performance of RFBs, with or without inclusion of suspended solids 205-210.
  • FIG. 2B is a schematic diagram illustrating a metal/slurry flow redox battery 250, in accordance with embodiments of the present disclosure.
  • Metal/slurry RFBs ( Figure 2b) employ a slurry on one side of the battery and a metal plate electrode 255 on the other side. Metal electrodes can dissolve and reform during charge-discharge cycling. In some cases, relatively large numbers of cycles can result in parasitic dendrite formation on the surface of metal plate electrode 255. As would be understood by a person having ordinary skill in the electrochemical arts, parasitic dendrite formation can result in short circuiting of electrochemical cells, surface fouling, or other performance impairments. To that end, the techniques described herein with respect to FIG. 3 and Example 1 can improve the performance of RFBs by replacing at least a portion of the metal/electrolyte flow redox configurations.
  • FIG. 3 is a schematic diagram illustrating a redox-targeting flow battery 300, in accordance with embodiments of the present disclosure.
  • Redox-targeting flow batteries (or "flow-mediated" batteries) store redox-active solids 305 in the electrolyte tanks 105-110.
  • the electrolyte functions as a redox mediator that transports electrons between the electrochemical cell 150 and the redox-active solids 305 in the tank.
  • redox-active molecules (A) first become electrochemically oxidized (A + ) at anode 130.
  • Catholyte and Anolyte molecules 310 are circulated back into tanks 105- 110, where they undergo chemical reactions with redox-active solid 305 to regenerate electrolytes 115-120.
  • electrochemical reactions in equations (1) and (2) are reversed.
  • catholyte 115 is reduced at electrode 125 and oxidized by direct chemical reaction with redox active solid 305 in catholyte tank 105.
  • the overall charge capacity of the RFB is significantly improved based at least in part on regeneration of electrolytes 115-120.
  • at least partially replacing suspended solids 205-210 with the redox active solid 305 configurations of example system 300 can reduce or entirely eliminate performance impairment associated with slurry circulation or parasitic dendrite formation on electrodes.
  • T1O2 can serve as a redox-active solid 305, with cobaltocene and decamethylcobaltocene as redox mediator molecules 310.
  • Such organometallic compounds exhibit significant air and moisture sensitivity, limiting demonstrations of T1O2 systems to lab-scale demonstrations in a strictly inert environment, which is understandably inapplicable to pilot, commercial, and/or industrial scale application.
  • a polyaniline/carbon-black composite added to an aqueous y 4+/3+ anolyte can potentially function as in a redox targeting RFB, (e.g providing a boost in capacity for the catholyte (Fe 2+/3+ )), the g 4+/3+ redox couple is understood to be unsuitable as a redox mediator due to its relatively slow reaction kinetics.
  • Prussian blue can potentially function as a redox-active additive in Br2/Br catholytes but is limited to a relatively low operating voltage (0.67 V) that has negative implications for commercial application, as power and reaction rate depend at least in part on operating voltage.
  • a robust, aqueous redox-targeting anolyte with high operating voltage, using low-cost materials and showing high cyclability involves application of different redox active solids 305 and electrolytes 115-120.
  • an aqueous redox flow battery in accordance with example systems 100, 200, 250, or 300 includes an aqueous electrolyte 115 and/or 120 including a redox-active additive and the redox mediator.
  • the redox-active additive can be or include redox- active solid 305.
  • the redox active additive is different for cathode-side and anode-side half-cells.
  • catholyte tank 105 can include a first redox-active solid 305-1 that is different from a second redox active solid 305-2 that is disposed in anolyte tank 110.
  • the redox-active additive includes titanium (Ti), lead (Pb), iron (Fe), zinc (Zn), tin (Sn), copper (Cu), nickel (Ni), cobalt (Co), bismuth (Bi), sodium (Na), lithium (Li), magnesium (Mg), compounds thereof, oxides thereof, complexes thereof, salts thereof, or any combination thereof.
  • the redox-active additive includes Ti, Zn, Li, compounds thereof, oxides thereof, complexes thereof, salts thereof, or any combination thereof.
  • the redox- active additive comprises a redox-active metal.
  • aqueous redox flow batteries of systems 100, 200, 250, and/or 300 can exhibit increased energy storage capacity.
  • energy storage capacity of aqueous redox flow batteries can be increased by at least 1%, by at least 5%, by at least 10%, by at least 15%, by at least 20%, by at least 25%, by at least 30%, by at least 40%, by at least 45%, by at least 50%, by at least 55%, by at least 60%, by at least 65%, by at least 70%, by at least 75%, by at least 80%, by at least 85%, by at least 90%, by at least 95%, by at least 100%, or more, including fractions and interpolations thereof, as compared to the energy storage capacity of an aqueous redox flow battery deployed the redox-active additive in the aqueous electrolytes 115 and/or 120.
  • the redox-active additive comprises zinc metal.
  • the zinc metal can be in the form of a powder, mossy zinc, zinc mesh, electrodeposited zinc, zinc foam, zinc pellets or any combination thereof.
  • the redox-active additive can be in the form of a powder.
  • the redox-active additive is insoluble in at least one of a reduced form or an oxidized form in the aqueous electrolyte 115 and/or 120.
  • the water-soluble redox mediator 310 comprises a redox potential within about +/- 10 mV, within about +/- 20 mV, within about +/- 30 mV, within about +/- 40 mV, within about +/- 50 mV, within about +/- 60 mV, within about +/- 70 mV, within about +/- 80 mV, within about +/- 90 mV, within about +/- 100 mV, within about +/- 110 mV, within about +/- 120 mV, within about +/- 130 mV, within about +/- 140 mV, within about +/- 150 mV, within about +/- 160 mV, within about +/- 170 mV, within about +/- 180 mV, within about +/- 190 mV, within about +/- 200 mV, within about +/- 210 mV, within about +/- 220 mV, within about +/- 230 m
  • a redox mediator 310 to be paired with redox active solid 305 corresponds with the similarity of redox potential of the two or more materials. For example, deviations larger than +/- 200 mV in redox potential between the redox-active additive and the redox mediator can reduce the voltage efficiency of the respective half cells that impair RFB performance.
  • the redox mediator is water-soluble, such that electrolytes 115 and/or 120 can include water and a dissolved redox mediator.
  • the redox mediator can be or include a water-soluble aqueous transition metal salt, complex, coordination compound, or other molecule 310.
  • each half cell can include the same or different redox mediator.
  • cathode-side electrolyte 115 can include a first redox mediator and anode-side electrolyte 120 can include a second redox mediator, where first mediator and second mediator can be the same or different.
  • the redox mediator can be or include a transition metal coordination compound optionally including a ligand selected from triethanolamine, triisopropanolamine, bipyridine, porphyrins, bridging oxides, and any derivatives thereof.
  • the redox mediator can be or include a water-soluble organometallic compound.
  • the redox mediator can be or include an aqueous organoiron compound, including but not limited to [Fe(TEOA)OH] 1_/2 - and/or [Fe(TiPA)OH]
  • the redox mediator can be dissolved in electrolytes 115 or 120, in addition to or in place of a particulate slurry.
  • example system 100, 200, 250, or 300 can include electrolytes 115 and/or 120 that incorporate the redox mediator and can include redox- active additive at a molar ratio of from about 1:0.1 to about 1:25, where the ratio notation describes the relative molar quantity of redox-active additive for a unit mole of redox mediator.
  • the redox-active additive can be included in tanks 105 and/or 110 at a molar ratio of about 0.01, about 0.1, about 0.5, about 1.0, about 1.5, about 2.0, about 2.5, about 3.0, about 3.5, about 4.0, about 4.5, about 5.0, about 5.5, about 6.0, about 6.5, about 7.0, about 7.5, about 8.0, about 8.5, about 9.0, about 9.5, about 10, about 11, about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, about 25, about 30, about 35, about 40, about 45, about 50, for a mole of redox mediator, including fractions and interpolations thereof.
  • electrolyte 115 and/or 120 can include the redox mediator at a concentration from about 0.1 M to about 5 M.
  • redox mediator concentration can be about 0.1 M, about 0.2 M, about 0.3 M, about 0.4 M, about 0.5 M, about 0.6 M, about 0.7 M, about 0.8 M, about 0.9 M, about 1.0 M, about 1.1 M, about 1.2 M, about 1.3 M, about 1.4 M, about 1.5 M, about 1.6 M, about 1.7 M, about 1.8 M, about 1.9 M, about 2.0 M, about 2.1 M, about 2.2 M, about 2.3 M, about 2.4 M, about 2.5 M, about 2.6 M, about 2.7 M, about 2.8 M, about 2.9 M, about 3.0 M, about 3.1 M, about 3.2 M, about 3.3 M, about 3.4 M, about 3.5 M, about 3.6 M, about 3.7 M, about 3.8 M, about 3.9 M, about 4.0 M, about 4.1 M, about 4.2 M, about 4.3
  • electrolyte concentration With respect to redox mediator concentration, higher concentrations improve energy density of electrolytes, limited by saturation point and precipitation dynamics.
  • the electrolyte concentration can be further improved by adding suspended or dispersed redox-active additive to electrolytes to be circulated with electrolytes and redox mediator.
  • example systems 100, 200, 250, and or 300 can be configured to operate as an aqueous redox flow battery.
  • the aqueous redox flow battery can achieve a volumetric power density from about 5 Wh/L to about 200 Wh/L.
  • volumetric power density can be used as a figure of merit that carries a unit of Watt-hours per liter, which describes a cell-size normalized electrical performance of the aqueous redox flow battery.
  • relative performance of embodiments of the present disclosure as compared to conventional technologies can be determined based at least in part on the value of volumetric power density.
  • volumetric power density is a common figure of merit for RFBs, much like mAh is a common figure of merit for conventional batteries.
  • higher volumetric power densities reflect improved power per unit of electrolyte volume.
  • Improved volumetric power density in turn improves charge/discharge time for an RFB and improves peak power output.
  • a typical power density is about 20 Wh/L.
  • the volumetric power density of a system configured to operate as a redox flow battery can achieve a volumetric power density of about 5 Wh/L or less, from about 5 Wh/L to about 10 Wh/L, from about 5 Wh/L to about 15 Wh/L, from about 5 Wh/L to about 20 Wh/L, from about 5 Wh/L to about 25 Wh/L, from about 5 Wh/L to about 30 Wh/L, from about 5 Wh/L to about 35 Wh/L, from about 5 Wh/L to about 40 Wh/L, from about 5 Wh/L to about 45 Wh/L, from about 5 Wh/L to about 50 Wh/L, from about 5 Wh/L to about 55 Wh/L, from about 5 Wh/L to about 60 Wh/L, from about 5 Wh/L to about 65 Wh/L, from about 5 Wh/L to about 70 Wh/L, from about 5 Wh/L
  • embodiments of the aqueous redox flow battery can be maintained substantially free of dendrites formed from the redox-active additive.
  • dendrites formed of metal and/or redox-active additives can significantly impair the performance and lifetime of and RFB, for example, by shorting one or more cells 150 of the RFB or by puncturing separator 140 and causing cross-contamination of electrolytes between half cells (e.g., when the RFB includes multiple cells in parallel and/or in series).
  • At least in part due to the localization of electrochemical reactions (1) and (2) with the redox-active additive to tanks 105 and/or 110 plating of redox-active additives onto electrodes 125-130 is relatively disfavored, thereby reducing the formation of dendrites at or near electrodes 125 and/or 130.
  • an aqueous redox flow battery include negative electrolyte tank 110 including a negative aqueous electrolyte 120 comprising a redox-active additive 305-2 and a water-soluble redox mediator as described above.
  • the aqueous RFB can include negative electrode 130 fluidically coupled with the negative electrolyte tank 110 and a positive electrolyte tank 105 including a positive electrolyte 115.
  • positive electrolyte 115 includes a water-soluble redox mediator as described above.
  • Positive electrode 125 can be fluidically coupled with positive electrolyte tank 105. In this way, cell 150 can be divided into two half cells by an ion-permeable separator 140 between 130 negative electrode and positive electrode 125.
  • FIG. 4 is a block flow diagram of an example process 400 for operating an aqueous RFB configured as described above, in accordance with embodiments of the present disclosure.
  • operating the aqueous RFB in accordance with example process 400 includes one or more operations that can be reordered, omitted, repeated, cycled, and/or performed at least partially in parallel.
  • the sequence of operations illustrated in FIG. 4 is intended to illustrate an example rather than a limiting embodiment.
  • embodiments include systems where at least one cell 150 can charge and at least one cell 150 can discharge concurrently, for example, through inclusion of electronic control circuitry that permits different cells 150 to be electronically coupled with different load/charge circuits.
  • example process 400 can improve the performance, responsiveness, and efficiency of an aqueous RFB that includes multiple cells 150.
  • electrochemical reactions occurring in tanks 105 and 110 are agnostic as to the number of charging cells and discharging cells. Instead, the net reaction balance between charging and discharging determines at least in part the reactions that occur at redox-active additive.
  • the flowrates through respective tanks 105 and 110 can be controlled by monitoring system operating parameters at tanks 105 and 110 and by net electrical parameters at circuitry 145, instead of measuring flowrate through individual cells.
  • example process 400 includes charging the aqueous redox flow battery.
  • Charging can include inducing a current through cell 150 at a current density of from about 10 mA/cm2 to about 400 mA/cm2.
  • block 405 can include applying a voltage from about 0.5 V to about 1.8 V to the aqueous redox flow battery using an external power circuit (e.g., circuitry 145 of FIG. 3).
  • charging can include inducing the reverse of reactions (1) and (2) on the anode side to store charge as chemical potential energy in tank 110. In this way, charging can be applied to both tanks 105 and 110 or individual tanks 105 or 110.
  • the voltage is determined by the difference between the reduction potentials of the anolyte and catholyte. Higher operating currents increase the power, which is a significant challenge preventing grid-scale application of RFB systems.
  • example process 400 includes storing charge in tanks 105 and 110 for a period of time.
  • tanks 105 and/or 110 can store charge for a period of time until demand triggers a switch from charging to discharge operation.
  • example systems 100, 200, 250 and/or 300 can service peaking demand and/or can function as distributed storage for intermittent energy sources including but not limited to distributed solar, wind, tidal, or other environmentally sustainable sources of electrical generation capacity.
  • example process 400 includes discharging the aqueous RFB, for example, by reversibly coupling cell 150 to an external load (e.g., as part of circuitry 145).
  • the aqueous RFB can be physically connected to a load circuit via a mechanical relay that is actuated by control circuitry configured to monitor electricity supply and demand on a circuit to which the aqueous RFB is connected (e.g., a local or regional distribution grid) and to switch cell(s) 150 from charge to discharge operation in response to demand exceeding supply.
  • control circuitry configured to monitor electricity supply and demand on a circuit to which the aqueous RFB is connected (e.g., a local or regional distribution grid) and to switch cell(s) 150 from charge to discharge operation in response to demand exceeding supply.
  • flow direction can be maintained without affecting performance of cell(s) 150.
  • Flow directions can be maintained due, at least in part, because the redox-active additive can be reduced or oxidized by the water-soluble redox mediator in tanks 105 and/or 110, thereby relocating at least a part of the electrochemical reaction to tanks 105 and/or 110.
  • the aqueous redox flow battery when configured as described above can remain essentially free of dendrites formed from the redox-active additive over multiple cycles of example process 400.
  • the anode can remain essentially free of dendrites formed from the redox-active additive when subjected to about 10 charge/discharge cycles, about 20 cycles, about 30 cycles, about 40 cycles, about 50 cycles, about 60 cycles, about 70 cycles, about 80 cycles, about 90 cycles, about 100 cycles, or more than 100 cycles, including fractions and interpolations thereof. Dendrite formation is generally understood to impair the functioning of aqueous RFBs.
  • aqueous RFBs can exhibit improved performance as power storage and delivery systems while also exhibiting improved lifetime, relative to the conventional approaches described in reference to FIGs. 1-2B.
  • the aqueous redox flow battery can operate over a similar number of charge/discharge cycles with essentially negligible formation of deposits of redox-active additive on electrodes 125 or 130.
  • the anode can remain essentially fee of deposits when subjected to at least 100 charge/discharge cycles.
  • deposits refers to plating during discharge or charge, as appropriate, of electrodes 125 or 130 with additive.
  • Such deposits can introduce resistive barriers and can affect the electrochemical reactions (e.g., the galvanic properties of the electrochemical cell) and impair performance of cell(s) 150. For that reason, lifetime of the aqueous RFB is directly related to the number of charge/discharge cycles over which electrodes 125 and/or 130 remain essentially free of deposits.
  • example process 400 optionally includes refreshing redox additive and/or redox mediator at block 420.
  • Refreshing in this context refers to medium exchange and or replacing the contents of cell(s) 150 and/or tanks 105 and/or 110.
  • Block 420 can improve the operational lifetime of example systems 100, 200, 250, or 300, for example, by replacing fouled additive or spent mediator with fresh materials.
  • block 420 can be repeated once for a number of cycles. For example, block 420 can be implemented every 100 charge/discharge cycles, every 1000 charge/discharge cycles, every 10,000 charge/discharge cycles, or more, including fractions and interpolations thereof.
  • maintenance procedures as in block 420 can include significant downtime for systems, such that exceedingly frequent refreshing operations can impair system performance. Conversely, however, exceedingly infrequent refreshing can impair performance through fouling or other undesirable competing reactions between electrolytes 115 and/or 120 and system components.
  • EXAMPLE 1 REDOX- ACTIVE SOLID ADDITIVES FOR AQUEOS REDOX FLOW
  • an inexpensive, earth-abundant aqueous redox-targeting anolyte includes an iron-based anolyte 120 as suitable redox mediator for reversible redox reactions with solid zinc additives 305 in water.
  • mediator/solid redox reactions were be monitored using UV-vis absorption spectroscopy and an iron-based anolyte 120 system was evaluated for flow battery applications (e.g., for use in example system 300) in conjunction with an iron-based catholytes 115.
  • aqueous RFB s have been demonstrated that operate at 1.1 V and demonstrate improved cyclability relative to techniques described in reference to FIGs. 2A-2B and the preceding redox-targeting configurations. Addition of the redox-active solid 305 showed an 84% increase in capacity relative to the same RFB prior to solid addition.
  • Triethanolamine (TEOA, 99.0%) and zinc oxide powder (ZnO, > 99.0%) were purchased from Sigma Aldrich.
  • Iron (II) chloride tetrahydrate (FcCh'dfLO, 99%) was purchased from Alfa Aesar.
  • Iron (III) chloride hexahydrate (FcCl ⁇ b!LO, 99.7%) and sodium hydroxide pellets were purchased from Fisher Chemicals.
  • Potassium ferricyanide (K3[Fe(CN)6, 99.9%) and zinc powder (purified) were purchased from J.T. Baker. All chemicals were used without further purification.
  • Electrolyte preparation The 1.0 M [Fe(CN) 6 ] 3 catholyte was prepared by dissolving K3[Fe(CN)6] in 0.5 M NaOH solution.
  • the [Fe(TEOA)OH] 2 anolyte was prepared by first dissolving 3.96 g (20 mmol) FcCh'dfFO in 21 mL of deionized water with stirring and N2 sparging for 20 minutes to form a light green solution. Then, 2 equivalents of TEOA (5.4 mL, 40 mmol) were added to the Fe 2+ flask, upon which a pastel- blue slurry was formed.
  • Fuel cell hardware was purchased from Fuel Cell Technologies (Albuquerque, NM).
  • the active area was 5 cm 2 with a machined serpentine flow pattern on graphite blocks that were treated with a cured furan resin. 0.01" silicone gaskets were used on both plates.
  • the electrodes were carbon cloth (Panex PW03, 0.4 mm uncompressed thickness, Zoltek Carbon Fiber).
  • the ion exchange membrane (Nafion 115) was soaked in 1.0 M NaOH solution for at least an hour prior to assembling the cell. Electrolytes were stored in 50 mL centrifuge tubes with holes in their caps.
  • a Masterflex L/S peristaltic pump and Chem-Durance Bio L/S 14 tubing were used to pump the electrolytes through the electrochemical cell (100 - 150 rpm).
  • a Squidstat potentiostat (Admiral Instruments) was used for charge/discharge measurements. The potential limits were set from 1.6 - 0.5 V, and the current was set between 200 - 400 mA (40 - 80 mA cm 2 ). All measurements were performed at room temperature with no active temperature control at the electrochemical cell or electrolyte tanks. Setup as described is illustrated in FIGs. 12A-B.
  • [Fe(TEOA)OH] 2 loses an electron upon discharge at a redox potential of -1.02 V vs Ag/AgCl (eq 3), and [Fe(CN) 6 ] 3 gains an electron upon discharge at a redox potential of +0.27 V vs Ag/AgCl (eq 4).
  • the RFB composed of these redox pairs is therefore expected to have a maximum cell potential of 1.29 V.
  • FIG. 6 shows UV-vis absorption spectra of the fully charged ([Fe(TEOA)OH] 2 , dashed line) and fully discharged ([Fe(TEOA)OH] , solid line) form of the anolyte.
  • [Fe(TEOA)OH] was prepared by electrochemical oxidation.
  • the fully charged anolyte is characterized by a strong absorption band in the NIR around 920 nm. In the fully discharged anolyte, this NIR absorption feature is mostly absent and the spectrum is characterized by peaks in the visible around 473 and 560 nm.
  • the [Fe(TEOA)OH] 2 spectrum shows substantial scattering at high concentrations.
  • Zinc metal was identified as a candidate for redox-targeting due to its redox potential and low cost. It was determined that the redox potential of Zn should be sufficient to reduce [Fe(TEOA)OH] to [Fe(TEOA)OH] 2 (eq 5). To that end, redox reactions were monitored between [Fe(TEOA)OH] and Zn powder by absorption spectroscopy.
  • FIG. 7A shows the absorption spectrum of [Fe(TEOA)OH] (black solid curve), measured at an iron concentration of 0.1 M to facilitate transmission.
  • FIG. 7B shows the absorption spectrum of [Fe(TEOA)OH] 2 (black solid curve), also at 0.1 M concentration.
  • FIG. 8 shows charge/discharge voltage curves measured at a current density of 40 mA cm 2 .
  • the voltage limits were set limiting the operation range to 1.6 - 0.5 V to avoid unwanted side reactions.
  • the average charge and discharge times were 1.98 and 1.91 hours, respectively.
  • FIG. 9A plots the charge (top curves) and discharge (bottom curves) capacity (mAh) vs voltage for two full charge/discharge cycles, before and after the addition of Zn powder to the anolyte tank, measured at a current density of 80 mA cm 2 .
  • the volumetric charge capacity (Ah L 1 ) is shown on the top axis.
  • FIG. 9B plots capacity (mAh, left axis) and increase in capacity (%, right axis) against the equivalents of Zn added to the anolyte tank.
  • a volumetric power density of 10 Wh L 1 is estimated from the volumetric discharge capacity after adding 0.6 equivalents of Zn (9.1 Ah L 1 ) and the average discharge voltage (-1.1 V). This power density already compares favorably to other published RFB systems and is expected to increase substantially with further optimization.
  • Electrochemical cells were disassembled after RFB measurements and inspected visually. No zinc deposits were observed by eye on the electrodes, membrane, or in the flow fields, regardless of whether the cell was disassembled after full charging or complete discharge. This observation suggests that soluble Zn 2+ species are not themselves being reduced at the electrodes, and instead suggests reduction of Zn 2+ by soluble [Fe(TEOA)OH] 2 . This chemistry is presently under investigation.
  • FIG. 10A and FIG. 10B show discharge capacity (mAh) and efficiency for six charge/discharge cycles with and without added Zn, respectively.
  • the efficiency is the ratio of measured capacity to theoretical capacity (429 mAh).
  • the Fe-TEOA concentration was lowered to 0.4 M and the TEOA:Fe ratio was varied.
  • the discharge capacity is increased to -355 mAh (FIG. 10A), despite a lower Fe concentration (0.4 M vs 0.5 M).
  • Example 4 used triisopropanolamine (TiPA) as the ligand.
  • Aqueous redox-targeting anolyte Use of a redox-targeting anolyte system in RFBs is described that uses an inexpensive aqueous redox mediator paired with an inexpensive, earth- abundant redox-active solid additive.
  • implementing anolyte systems with catholyte systems provides further performance improvements, for example, following optimization of the anolyte 120 composition (e.g ., amount of Zn added), and by variation of the ligands coordinating the Fe 2+/3+ redox mediator.
  • an iron- triisopropanolamine (Fe-TiPA) complex can be implemented as having electrochemical properties similar to Fe-TEOA.
  • the redox-targeting strategy described herein is generalizable to a broad class of inorganic or organometallic compounds with redox potentials configured for pairing with Zn additive (e.g., about -1.02 V vs Ag/AgCl).
  • Zn additive e.g., about -1.02 V vs Ag/AgCl.
  • Redox-active solid additive Measurements presented herein demonstrate increased RFB capacity with the addition of Zn powder to anolyte tank 110. RFB performance can be improved and/or optimized based at least in part on parametric-guided modification of the quantity and form of the added Zn redox active solids 305. Table 2: Influence of additive on capacity of RFB embodiments
  • Tables 2 and 3 illustrate the influence of additive inclusion and of stirring electrolyte 120 in anolyte tank 110 on RFB performance in the RFB system described in the context of Example 1. Data presented were determined from cell potential measurements made using the setup illustrated in FIGs. 12A-12B, as illustrated in FIG. 13 and FIG. 14 for Table 2 and Table 3, respectively.
  • Inclusion of redox-active additive and stirring or other mechanical agitation can improve one or more performance metrics for RFB, as well as performing at or above comparative examples described in Table 1 with respect to one or more properties shared in common with the examples. For example, with 0.4 molar additive, efficiency in Table 2 increases to 98.21 percent, which exceeds each comparative example described in Table 1. Similarly, discharge time increases, as illustrated in FIG. 11. Conclusion:
  • Example devices, methods, and systems are described herein. It should be understood the words “example,” “exemplary,” and “illustrative” are used herein to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as being an “example,” being “exemplary,” or being “illustrative” is not necessarily to be construed as preferred or advantageous over other embodiments or features.
  • FIGURES should not be viewed as limiting. It should be understood that other embodiments may include more or less of each element shown in a given FIGURE. Further, some of the illustrated elements may be combined or omitted. Yet further, an example embodiment may include elements that are not illustrated in the FIGURES.

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Abstract

L'invention concerne des systèmes, des dispositifs et des procédés de stockage et de décharge d'une batterie à flux redox aqueuse (RFB). Une batterie à flux redox aqueuse comprend un électrolyte aqueux comprenant un additif redox actif et un médiateur redox. L'additif redox-actif peut être ou comprendre, sans y être limité, du titane (Ti), du Plomb (Pb), du Fer (Fe), du zinc (Zn), de l'étain (Sn), du cuivre (Cu), du nickel (Ni), du cobalt (Co), du bismuth (Bi), du sodium (Na), du lithium (Li), du magnésium (Mg), leurs composés, leurs oxydes, leurs complexes, leurs sels ou toute combinaison de ceux-ci. Le médiateur redox peut être ou comprendre, sans y être limité, du composé de coordination de métaux de transition comprenant éventuellement un ligand choisi parmi la triéthanolamine, la triisopropanolamine, la bipyridine, les porphyrines, les oxydes de pontage et leurs dérivés.
PCT/US2022/015749 2021-02-11 2022-02-09 Batteries à flux redox aqueuse comprenant des additifs solides à activité redox WO2022173785A1 (fr)

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CN117239200A (zh) * 2023-11-14 2023-12-15 华中科技大学 一种铁溶解液、其制备方法和应用

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Publication number Priority date Publication date Assignee Title
US20140248521A1 (en) * 2008-06-12 2014-09-04 24M Technologies, Inc. High energy density redox flow device
US20170352905A1 (en) * 2012-07-27 2017-12-07 Lockheed Martin Advanced Energy Storage, Llc Aqueous redox flow batteries comprising metal ligand coordination compounds
WO2019245461A1 (fr) * 2018-06-22 2019-12-26 National University Of Singapore Batterie à flux redox à électrolyte aqueux

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Publication number Priority date Publication date Assignee Title
US20140248521A1 (en) * 2008-06-12 2014-09-04 24M Technologies, Inc. High energy density redox flow device
US20170352905A1 (en) * 2012-07-27 2017-12-07 Lockheed Martin Advanced Energy Storage, Llc Aqueous redox flow batteries comprising metal ligand coordination compounds
WO2019245461A1 (fr) * 2018-06-22 2019-12-26 National University Of Singapore Batterie à flux redox à électrolyte aqueux

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117239200A (zh) * 2023-11-14 2023-12-15 华中科技大学 一种铁溶解液、其制备方法和应用
CN117239200B (zh) * 2023-11-14 2024-02-20 华中科技大学 一种铁溶解液、其制备方法和应用

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