Abstract

During operation of flow battery systems, the volume of one or more electrolyte solutions can change due to solvent loss processes. An electrochemical balancing cell can be used to combat volume variability. Methods for altering the volume of one or more electrolyte solutions can include: providing a first electrochemical balancing cell containing a membrane disposed between two half-cells, establishing fluid communication between a first aqueous electrolyte solution of a flow battery system and a first half-cell of the first electrochemical balancing cell, and applying a current to the first electrochemical balancing cell to change a concentration of one or more components in the first aqueous electrolyte solution. Applying the current causes water to migrate across the membrane, either to or from the first aqueous electrolyte solution, and a rate of water migration is a function of current.

IPC Classes  ?

• H01M 8/04186 - Arrangements for control of reactant parameters, e.g. pressure or concentration of liquid-charged or electrolyte-charged reactants
• H01M 8/04276 - Arrangements for managing the electrolyte stream, e.g. heat exchange
• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• H01M 8/20 - Indirect fuel cells, e.g. fuel cells with redox couple being irreversible

Abstract

Crossover of active materials in an electrochemical cell can detrimentally impact operating performance, particularly for flow batteries. Flow batteries with tolerance toward crossover of active materials can incorporate a first half-cell containing a first electrolyte solution that includes a coordination complex as a first active material, and a second half-cell containing a second electrolyte solution that includes an unbound form of an organic compound as a second active material. The coordination complex contains a redox-active metal center and an organic compound bound to the redox-active metal center. The unbound form of the organic compound in the second electrolyte solution is the same as the bound organic compound in the first electrolyte solution, or an oxidized or reduced variant thereof. Catechol and substituted catechols can be particularly desirable organic compounds for inclusion in the coordination complex and the second electrolyte solution.

IPC Classes  ?

• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells

Abstract

Coordination complexes can have a metal center with at least one unsubstituted catecholate ligand and at least one monosulfonated catecholate ligand or a salt thereof bound thereto. Some coordination complexes can have a formula of DgTi(L1)x(L2)y, in which D is a counterion selected from NH4+, Li+, Na+, K+, or any combination thereof; g ranges between 2 and 6; L1 is an unsubstituted catecholate ligand; L2 is a monosulfonated catecholate ligand; and x and y are non-zero numbers such that x+y = 3. Methods for synthesizing such coordination complexes can include providing a neat mixture of catechol and a sub-stoichiometric amount of sulfuric acid, heating the neat mixture to form a reaction product containing catechol and a monosulfonated catechol or a salt thereof, and forming a coordination complex from the reaction product without separating the catechol and the monosulfonated catechol or the salt thereof from one another.

IPC Classes  ?

• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• H01M 10/056 - Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
• H01M 10/42 - Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells

Abstract

Solids can sometimes form in one or more electrolyte solutions during operation of flow batteries and related electrochemical systems. Over time, the solids can accumulate and compromise the integrity of flow pathways and other various flow battery components. Flow batteries configured for mitigating solids therein can include an autonomous solids separator, such as a lamella clarifier. Such flow batteries can include a first half-cell containing a first electrolyte solution, a second half-cell containing a second electrolyte solution, a first flow loop configured to circulate the first electrolyte solution through the first half-cell, a second flow loop configured to circulate the second electrolyte solution through the second half-cell, and at least one lamella clarifier in fluid communication with at least one of the first half-cell and the second half-cell. A hydrocyclone can be used as an alternative to a lamella clarifier in some instances.

IPC Classes  ?

• H01M 2/38 - Arrangements for moving electrolytes

Abstract

Parasitic reactions, such as production of hydrogen and oxidation by oxygen, can occur under the operating conditions of flow batteries and other electrochemical systems. Such parasitic reactions can undesirably impact operating performance by altering the pH and/or state of charge of one or both electrolyte solutions in a flow battery. Electrochemical balancing cells can allow rebalancing of electrolyte solutions to take place. Electrochemical balancing cells suitable for placement in fluid communication with both electrolyte solutions of a flow battery can include: a first chamber containing a first electrode, a second chamber containing a second electrode, a third chamber disposed between the first chamber and the second chamber, an ion-selective membrane forming a first interface between the first chamber and the third chamber, and a bipolar membrane forming a second interface between the second chamber and the third chamber.

IPC Classes  ?

• H01M 8/04 - Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• H01M 10/42 - Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells

Abstract

Productive electrochemical reactions can often occur most effectively in proximity to a separator dividing an electrochemical cell into two half-cells. Parasitic reactions can often occur at locations more removed from the separator. Parasitic reactions are generally undesirable in flow batteries and other electrochemical systems, since they can impact operating performance. Flow batteries having a decreased incidence of parasitic reactions can include, a first half-cell containing a first electrode, a second half-cell containing a second electrode, a separator disposed between the first half-cell and the second half-cell and contacting the first and second electrodes, a first bipolar plate contacting the first electrode, and a second bipolar plate contacting the second electrode, where a portion of the first electrode or the first bipolar plate contains a dielectric material. The first electrode and the first bipolar plate still define a contiguous electrically conductive pathway when containing the dielectric material.

IPC Classes  ?

• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• H01M 2/16 - Separators; Membranes; Diaphragms; Spacing elements characterised by the material
• H01M 8/20 - Indirect fuel cells, e.g. fuel cells with redox couple being irreversible

Abstract

Parasitic reactions, such as production of hydrogen and oxidation by oxygen, can occur under the operating conditions of flow batteries and other electrochemical systems. Such parasitic reactions can undesirably impact operating performance by altering the pH and/or state of charge of one or both electrolyte solutions in a flow battery. Electrochemical balancing cells configured for addressing the effects of parasitic reactions can include: a first chamber containing a first electrode, a second chamber containing a second electrode, a third chamber disposed between the first chamber and the second chamber, an ion-selective membrane forming a first interface between the first chamber and the third chamber, and a bipolar membrane forming a second interface between the second chamber and the third chamber. Such electrochemical balancing cells can be placed in fluid communication with at least one half-cell of a flow battery.

IPC Classes  ?

• H01M 8/04 - Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• H01M 10/42 - Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells

Abstract

Titanium coordination complexes, particularly titanium catecholate complexes, can be attractive active materials for use in flow batteries. However, such coordination complexes can be difficult to prepare from inexpensive starting materials, particularly in aqueous solutions. Titanium oxychloride and titanium tetrachloride represent relatively inexpensive titanium sources that can be used for preparing such coordination complexes. Methods for preparing titanium catecholate complexes can include combining one or more catecholate ligands and titanium oxychloride in an aqueous solution, and reacting the one or more catecholate ligands with the titanium oxychloride in the aqueous solution to form the titanium catecholate complex. Titanium tetrachloride can be used as a precursor for forming the titanium oxychloride in situ. In some instances, the titanium catecholate complex can be isolated in a solid form, which can be substantially free of alkali metal ions.

IPC Classes  ?

• H01M 4/36 - Selection of substances as active materials, active masses, active liquids
• C07F 7/28 - Titanium compounds

Abstract

Electrolyte solutions for flow batteries and other electrochemical systems can contain a dissolved iron hexacyanide complex as an active material. Alkaline buffering can be desirable in such electrolyte solutions to promote stability of the active material. However, the buffer material can undesirably decrease solubility of the iron hexacyanide complex to unacceptable levels in some instances. Compositions with increased concentrations of iron hexacyanide can include an aqueous solution containing a dissolved iron hexacyanide complex, and a solid buffer material in contact with the aqueous solution. The solid buffer material is present at an amount greater than that needed to produce a saturation concentration of the solid buffer material in the aqueous solution. Flow batteries and other electrochemical systems can contain the compositions as an electrolyte solution. Electrolyte solutions containing active materials other than an iron hexacyanide complex can also be stabilized by using an appropriate solid buffer material.

IPC Classes  ?

• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• H01M 8/20 - Indirect fuel cells, e.g. fuel cells with redox couple being irreversible
• C01C 3/08 - Simple or complex cyanides of metals
• C01C 3/12 - Simple or complex iron cyanides

Abstract

State of charge determination within electrochemical systems, such as flow batteries, can often be difficult to measure, particularly in an in situ manner. Methods for assaying the condition of an electrochemical system can include: interacting electromagnetic radiation with a first electrolyte solution at a location within the electrochemical system, the electromagnetic radiation being delivered through an optical material configured to exhibit attenuated total reflectance at an interface between the optical material and the first electrolyte solution; receiving at a detector electromagnetic radiation that has interacted with the first electrolyte solution via one or more attenuated total reflectances within the optical material; and measuring an absorbance of at least one of an oxidized form or a reduced form of a first coordination compound within the first electrolyte solution via the electromagnetic radiation that is received at the detector.

IPC Classes  ?

• G01N 27/30 - Electrodes, e.g. test electrodesHalf-cells
• G01N 21/55 - Specular reflectivity
• G01N 21/35 - Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light

Abstract

Active materials for flow batteries can include various coordination compounds formed from transition metals. Some compositions containing coordination compounds can include a substituted catecholate ligand having a structure of in a neutral form or a salt form, in which Z is a heteroatom functional group bound to the substituted catecholate ligand at an open aromatic ring position and n is an integer ranging between 1 and 4. When more than one Z is present, each Z can be the same or different. Electrolyte solutions can include such coordination compounds, and such electrolyte solutions can be incorporated within a flow battery.

IPC Classes  ?

• C07F 7/28 - Titanium compounds

Abstract

The invention concerns methods of determining the state of charge of a half-cell within a redox flow battery, the method comprising: (i) measuring the rate of change in equilibrium half- cell reduction potential of the electrolyte as charge is passed into the electrolyte solution within the cell; and (ii) correlating said rate of change in equilibrium half-cell reduction potential with the state of charge of said half-cell. Other aspects of the invention concern balancing the state of charge of a flow battery and methods of calibrating an oxidation/reduction probe.

IPC Classes  ?

• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• H01M 8/20 - Indirect fuel cells, e.g. fuel cells with redox couple being irreversible
• H01M 8/02 - Fuel cellsManufacture thereof Details

Abstract

The invention concerns redox flow batteries comprising one or more electrochemical cells in fluid contact with an electrochemical balancing cell, the balancing cell comprising: (i) a first electrode comprising a gas diffusion electrode and the first electrode comprising a hydrogen oxidation catalyst, wherein the first electrode being maintained at a potential more positive than the thermodynamic potential for hydrogen evolution; (ii) a second electrode, the second electrode contacting negative electrolyte, and the second electrode being maintained at a potential sufficiently negative to reduce the negative electrolyte; (iii) a membrane disposed between the positive electrode and the negative electrode, the membrane suitable to allow hydrogen cations to flow from the membrane to the negative electrolyte; and (iv) a means for contacting hydrogen with the first electrode.

IPC Classes  ?

• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• H01M 8/02 - Fuel cellsManufacture thereof Details
• H01M 4/86 - Inert electrodes with catalytic activity, e.g. for fuel cells

Abstract

The present invention relates to methods and apparatuses for determining the ratio of oxidized and reduced forms of a redox couple in solution, each method comprising: (a) contacting a first stationary working electrode and a first counter electrode to the solution; (b) applying a first potential at the first working electrode and measuring a first constant current; (c) applying a second potential at the first working electrode and measuring a second constant current; wherein the sign of the first and second currents are not the same; and wherein the ratio of the absolute values of the first and second currents reflects the ratio of the oxidized and reduced forms of the redox couple in solution. When used in the context of monitoring / controlling electrochemical cells, additional embodiments include those further comprising (d) oxidizing or reducing the solution, so as to alter the balance of the oxidized and reduced forms of the redox couple in solution, to a degree dependent on the ratio of the absolute values of the first and second currents. These embodiments may be used in the context of maintaining an electrochemical cell, stack, or system.

IPC Classes  ?

• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• H01M 8/02 - Fuel cellsManufacture thereof Details
• H01M 4/86 - Inert electrodes with catalytic activity, e.g. for fuel cells

Abstract

The present invention relates to redox flow batteries and methods and apparatuses for monitoring the compositions of the electrolytes therein. In particular, the present invention relates to methods and configurations for monitoring the state-of-charge of an electrolyte stream of a flow cell or flow battery.

IPC Classes  ?

• H01M 2/36 - Arrangements for filling, topping-up or emptying cases with or of liquid, e.g. for filling with electrolytes, for washing-out
• H01M 2/38 - Arrangements for moving electrolytes
• H01M 10/02 - Details

Abstract

The present invention is directed to a redox flow battery comprising at least one electrochemical cell in fluid communication with a balancing cell, said balancing cell comprising: a first and second half-cell chamber, wherein the first half-cell chamber comprises a first electrode in contact with a first aqueous electrolyte of the redox flow battery; and wherein the second half-cell chamber comprises a second electrode in contact with a second aqueous electrolyte, said second electrode comprising a catalyst for the generation of O2.

IPC Classes  ?

• H01M 8/06 - Combination of fuel cells with means for production of reactants or for treatment of residues
• H01M 8/18 - Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
• H01M 8/20 - Indirect fuel cells, e.g. fuel cells with redox couple being irreversible

Abstract

The present inventions are directed to fluid flow assemblies, and systems incorporating such assemblies, each assembly comprising a conductive element disposed within a non- conductive element; the non-conductive element being characterized as framing the conductive central element and the elements together defining a substantially planar surface when engaged with one another; each of the conductive and non-conductive elements comprising channels which, when taken together, form a flow pattern on the substantially planar surface; and wherein the channels are restricted, terminated, or both restricted and terminated in the non-conductive element.

IPC Classes  ?

• H01M 8/02 - Fuel cellsManufacture thereof Details
• B65B 1/04 - Methods of, or means for, filling the material into the containers or receptacles

Abstract

Stable solutions comprising charged coordination complexes, including iron hexacyanides are described, as are methods of preparing and using same in chemical energy storage systems, including flow battery systems. The use of these compositions allows energy storage densities at levels unavailable by other iron hexacyanide systems.

IPC Classes  ?

• C01C 3/12 - Simple or complex iron cyanides

Abstract

This invention is directed to aqueous redox flow batteries comprising ionically charged redox active materials and ionomer membranes, wherein the charge of the redox active materials is of the same sign as that of the ionomer, so as to confer specific improvements.

IPC Classes  ?

• H01M 4/13 - Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulatorsProcesses of manufacture thereof
• H01M 8/00 - Fuel cellsManufacture thereof

Abstract

This invention is directed to aqueous redox flow batteries comprising ionically charged redox active materials and separators, wherein the separator is about 100 microns or less and the flow battery is capable of (a) operating with a current efficiency of at least 85% with a current density of at least about 100 mA/cm2; (b) operating with a round trip voltage efficiency of at least 60% with a current density of at least about 100 mA/cm2; and / or (c) giving rise to diffusion rates through the separator for the first active material, the second active material, or both, of about 1x10-7 mol/cm2-sec or less.

IPC Classes  ?

• H01M 8/00 - Fuel cellsManufacture thereof
• H01M 4/13 - Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulatorsProcesses of manufacture thereof

Abstract

This invention is directed to aqueous redox flow batteries comprising redox-active metal ligand coordination compounds. The compounds and configurations described herein enable flow batteries with performance and cost parameters that represent a significant improvement over that previous known in the art.

IPC Classes  ?

• H01M 4/13 - Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulatorsProcesses of manufacture thereof
• H01M 8/00 - Fuel cellsManufacture thereof

Abstract

The invention concerns flow batteries comprising: a first aqueous electrolyte comprising a first redox active material; a second aqueous electrolyte comprising a second redox active material; a first electrode in contact with the first aqueous electrolyte; a second electrode in contact with the second aqueous electrolyte and a separator disposed between the first aqueous electrolyte and the second aqueous electrolyte; the flow battery having an open circuit potential of at least 1.4 V, and is capable of operating or is operating at a current density at least about 50 mA/cm2, wherein both of the first and second redox active materials remain soluble in both the charged and discharged states. In certain embodiments, the redox active materials are metal ligand coordination compounds. The disclosure also describes systems comprising these flow batteries and methods of them.

IPC Classes  ?

• H01M 4/13 - Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulatorsProcesses of manufacture thereof
• H01M 8/00 - Fuel cellsManufacture thereof

Abstract

The invention concerns flow batteries comprising: a first half-cell comprising: (i) a first aqueous electrolyte comprising a first redox active material; and a first carbon electrode in contact with the first aqueous electrolyte; (ii) a second half-cell comprising: a second aqueous electrolyte comprising a second redox active material; and a second carbon electrode in contact with the second aqueous electrolyte; and (iii) a separator disposed between the first half-cell and the second half-cell; the first half-cell having a half-cell potential equal to or more negative than about -0.3 V with respect to a reversible hydrogen electrode; and the first aqueous electrolyte having a pH in a range of from about 8 to about 13, wherein the flow battery is capable of operating or is operating at a current density at least about 25 mA/cm2 .

IPC Classes  ?

• H01M 4/13 - Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulatorsProcesses of manufacture thereof
• H01M 8/00 - Fuel cellsManufacture thereof