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: contacting first and second stationary working electrodes and first and second counter electrode to the solution; applying a first potential at the first stationary working electrode and a second potential at the second stationary working electrode relative to the respective counter electrodes and measuring first and second constant currents for the first and second stationary working electrodes, respectively; wherein the first and second constant currents have opposite signs and the ratio of the absolute values of the first and second constant 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 oxidizing or reducing the solution.

Abstract: Provided are flow batteries that include a fluidic train within a dynamic fluidic network system which fluidic train is convertible between a first state and a second state, the first state the first state placing a main electrolyte source and a dynamic fluidic network, outside the fluidic train and an electrode region, into fluid communication with the electrode region and the second state placing the main electrolyte source and the dynamic fluidic network, outside the fluidic train and the electrode region, into fluid isolation from the electrode region and placing the electrode region into fluid communication with a sampling segment. Also provided are methods of operating flow batteries.

Abstract: Provided are flow batteries that include a fluidic train within a dynamic fluidic network system which fluidic train is convertible between a first state and a second state, the first state the first state placing a main electrolyte source and a dynamic fluidic network, outside the fluidic train and an electrode region, into fluid communication with the electrode region and the second state placing the main electrolyte source and the dynamic fluidic network, outside the fluidic train and the electrode region, into fluid isolation from the electrode region and placing the electrode region into fluid communication with a sampling segment. Also provided are methods of operating flow batteries.

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 comprising a catalyst for the generation of O2; and wherein the second half-cell chamber does not contain an aqueous electrolyte.

Abstract: Flow batteries can include a first half-cell containing a first aqueous electrolyte solution. a second half-cell containing a second aqueous electrolyte solution, and a separator disposed between the first half-cell and the second half-cell. The first aqueous electrolyte solution contains a first redox-active material, and the second aqueous electrolyte solution contains a second redox-active material. At least one of the first redox-active material and the second redox-active material is a nitroxide compound or a salt thereof. Particular nitroxide compounds can include a doubly bonded oxygen contained in a ring bearing the nitroxide group, a doubly bonded oxygen appended to a ring bearing the nitroxide group, sulfate or phosphate groups appended to a ring bearing the nitroxide group, various heterocyclic rings bearing the nitroxide group, or acyclic nitroxide compounds.

Abstract: Provided are flow batteries that include a fluidic train within a dynamic fluidic network system which fluidic train is convertible between a first state and a second state, the first state the first state placing a main electrolyte source and a dynamic fluidic network, outside the fluidic train and an electrode region, into fluid communication with the electrode region and the second state placing the main electrolyte source and the dynamic fluidic network, outside the fluidic train and the electrode region, into fluid isolation from the electrode region and placing the electrode region into fluid communication with a sampling segment. Also provided are methods of operating flow batteries.

Abstract: Provided are assemblies, comprising: a first leaf spring; a second leaf spring; and at least one component; the first leaf spring and the second leaf spring being superposed over a first end of the at least one component so as to exert first and second forces, respectively, through first and second regions of the component. These assemblies are useful to apply different forces to a stacked assembly where a cross section of a component of the assembly comprises materials of different Young's moduli within that cross section, thereby compressing different regions of the component with different forces.

Abstract: Electrochemical cells, such as those present within flow batteries, can include at least one electrode with one face being more hydrophilic than is the other. Such electrodes can lessen the incidence of parasitic reactions by directing convective electrolyte circulation toward a separator in the electrochemical cell. Flow batteries containing the electrochemical cells can include: a first half-cell containing a first electrode with a first face and a second face that are directionally opposite one another, a second half-cell containing a second electrode with a first face and a second face that are directionally opposite one another, and a separator disposed between the first half-cell and the second half-cell. The first face of both the first and second electrodes is disposed adjacent to the separator. The first face of at least one of the first electrode and the second electrode is more hydrophilic than is the second face.

Abstract: Stable solutions comprising high concentrations of 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.

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 comprising a catalyst for the generation of O2; and wherein the second half-cell chamber does not contain an aqueous electrolyte.

Abstract: The present invention is directed to novel membrane electrode assemblies, and devices and systems incorporating them. Representative membrane electrode assemblies comprise (a) a first, porous electrode; (b) a buffer layer optionally comprising an aqueous solution comprising a pH buffer; (c) a membrane; and (d) a second, porous electrode comprising a catalyst for the generation of oxygen (O2); wherein the membrane is interposed between the first electrode and the second electrode, and the buffer layer is interposed between the membrane and the first electrode.

Abstract: Flow batteries can be constructed by combining multiple electrochemical unit cells together with one another in a cell stack. High-throughput processes for fabricating electrochemical unit cells can include providing materials from rolled sources for forming a soft goods assembly and a hard goods assembly, supplying the materials to a production line, and forming an electrochemical unit cell having a bipolar plate disposed on opposite sides of a separator. The electrochemical unit cells can have configurations such that bipolar plates are shared between adjacent electrochemical unit cells in a cell stack, or such that bipolar plates between adjacent electrochemical unit cells are abutted together with one another in a cell stack.

Abstract: The present disclosure is directed to methods for levelizing circulation rates over multiple electrochemical cells of an electrochemical cell stack due to a pressure drop that occurs at an outlet of each electrochemical cell.

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.

Abstract: Flow batteries can include a first half-cell containing a first aqueous electrolyte solution, a second half-cell containing a second aqueous electrolyte solution, and a separator disposed between the first half-cell and the second half-cell. The first aqueous electrolyte solution contains a first redox-active material, and the second aqueous electrolyte solution contains a second redox-active material. At least one of the first redox-active material and the second redox-active material is a nitroxide compound or a salt thereof. Particular nitroxide compounds can include a doubly bonded oxygen contained in a ring bearing the nitroxide group, a doubly bonded oxygen appended to a ring bearing the nitroxide group, sulfate or phosphate groups appended to a ring bearing the nitroxide group, various heterocyclic rings bearing the nitroxide group, or acyclic nitroxide compounds.

Abstract: Electrolyte solutions for flow batteries and other electrochemical systems can contain an active material that is capable of transferring one or more electrons per molecule during an oxidation-reduction cycle. Doubly bridged aromatic groups or their coordination compounds can be particularly suitable active materials. Flow batteries can include a first half-cell containing a first electrolyte solution, and a second half-cell containing a second electrolyte solution, in which at least one of the first electrolyte solution and the second electrolyte solution contains an active material having at least two aromatic groups doubly bridged by a carbonyl moiety and a bridging moiety containing a bridging atom selected from carbon, nitrogen, oxygen, sulfur, selenium and tellurium. Such bridged compounds can directly function as the active material, or coordination compounds containing the bridged compounds as at least one ligand can serve as the active material.

Abstract: The circulation rates of the electrolyte solutions in a flow battery can impact operating performance. Adjusting the circulation rates can allow improved performance to be realized. Flow battery systems having adjustable circulation rates can include a first half-cell containing a first electrolyte solution, a second half-cell containing a second electrolyte solution, at least one pump configured to circulate the first electrolyte solution and the second electrolyte solution at adjustable circulation rates through at least one half-cell in response to a value of Pexit/I or I/Penter, and at least one sensor configured to measure net electrical power entering or exiting the flow battery system, and an amount of electrical current passing through the whole cell. I is the electrical power passing through the whole cell. Pexit is net electrical power exiting the system in a discharging mode, and Penter is net electrical power entering the system in a charging mode.

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.

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.

Abstract: Titanium catecholate complexes can be desirable active materials for flow batteries and other electrochemical energy storage systems, particularly when incorporated in aqueous electrolyte solutions. It can be desirable to avoid introducing certain organic solvents and/or extraneous salts into aqueous electrolyte solutions. Methods for synthesizing titanium catecholate complexes that can help avoid the unwanted introduction of organic solvents and/or extraneous salts into aqueous electrolyte solutions can include: providing an aqueous solution containing a catechol compound, reacting a titanium reagent with the catechol compound in the aqueous solution to form an intermediate titanium catecholate complex, isolating the intermediate titanium catecholate complex as a solid or slurry, and reacting a ligatable compound with the intermediate titanium catecholate complex in the presence of a base to produce a salt form titanium catecholate complex containing at least one additional ligand.