Described herein is a polymeric electrolyte membrane for a redox flow battery comprising (i) a polymer, (ii) a plurality of pendent groups comprising a sulfonic acid, and (iii) a plurality of pendent groups comprising a sulfonamide.

The present specification relates to a compound comprising an aromatic ring, a polyelectrolyte membrane comprising the same, a membrane-electrode assembly comprising the polyelectrolyte membrane, a fuel cell comprising the membrane-electrode assembly, and a redox flow battery comprising the polyelectrolyte membrane.

Methods of determining concentrations and/or amounts of redox-active elements at each valence state in an electrolyte solution of a redox flow battery are provided. Once determined, the concentrations and/or amounts of the redox-active elements at each valence state can be used to determine side-reactions, make chemical adjustments, periodically monitor battery capacity, adjust performance, or to otherwise determine a baseline concentration of the redox-active ions for any purpose.

Redox flow battery 1 include cell frame 20 having recess 21, 22, at least one sheet-like electrode 11, 13 received in recess 21, 22, membrane 15 stacked on cell frame 20 to cover recess 21, 22, and bipolar current collecting member 40 penetrating cell frame 20 at recess 21, 22 and electrically connected to at least one electrode 11, 13, wherein cell frame 20 has flow channels 31-38 communicating with recess 21, 22 so as to allow a fluid containing an active material to flow through recess 21, 22 parallel to membrane 15, and wherein at least one electrode 11, 13 is disposed in recess 21, 22 at an angle where at least one electrode 11, 13 intersects membrane 15.

One embodiment is a redox flow battery system that includes an anolyte; a catholyte; an anolyte tank configured for holding at least a portion of the anolyte; a catholyte tank configured for holding at least a portion of the catholyte; a primary redox flow battery arrangement, and a second redox flow battery arrangement. The primary and secondary redox flow battery arrangements share the anolyte and catholyte tanks and each includes a first half-cell including a first electrode in contact with the anolyte, a second half-cell including a second electrode in contact with the catholyte, a separator separating the first half-cell from the second half-cell, an anolyte pump, and a catholyte pump. The peak power delivery capacity of the secondary redox flow battery arrangement is less than the peak power delivery capacity of the primary redox flow battery arrangement.

The present invention provides a regenerative fuel cell comprising an anionic membrane capable of selectively passing anions, wherein the pH of the anolyte and/or catholyte is at least 10. The present invention also relates to a method of operating a regenerative fuel cell comprising an anionic membrane capable of selectively passing anions, wherein the pH of the anolyte and/or catholyte is at least 10.

Devices and methods for managing the state of health of an electrolyte in redox flow batteries (RFB) efficiently are described. A diffusion cell is added to the RFB which controls one or more properties of the electrolytes using the diffusion of protons through a proton exchange membrane. The diffusion cell can resemble an electrochemical cell in that there are two fluid chambers divided by a proton conducting membrane. Anolyte flows through one side of the device where it contacts the proton conducting membrane, and catholyte flows through the second side of the device where it contacts the other face of the proton conducting membrane. The concentration gradient of protons from high concentration in the catholyte to low concentration in the anolyte is the driving force for proton diffusion, rather than electromotive force, which greatly simplifies the design and operation.

The present invention is to provide a hydrogen oxidation catalyst that does not contain platinum. Disclosed is a hydrogen oxidation catalyst that is a dinuclear transition metal complex having a chemical structure represented by the following general formula (1) or (2): ##STR00001##
wherein, in the general formulae (1) and (2), M.sup.1 and M.sup.2 are each independently Fe or Ru; Ar.sup.1 and Ar.sup.2 are each independently a cyclopentadienyl group or a pentamethylcyclopentadienyl group; Ar.sup.3 and Ar.sup.4 are each independently a divalent aromatic hydrocarbon group having 6 to 12 carbon atoms; and Ar.sup.5 is a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms, and in the general formula (2), R.sup.1 and R.sup.2 are each independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms.

The present invention relates to a method of preparing a high-purity electrolyte solution for a vanadium redox flow battery using a catalytic reaction, and more specifically, to a method of preparing a high-purity electrolyte solution having a vanadium oxidation state of +3 to +5 from a mixture solution containing a vanadium precursor, a reducing agent, and an acidic solution, by using a catalyst. By using a catalyst and a reducing agent that does not leave impurities such as Zn.sup.2+, which are generated when preparing electrolyte solutions using an existing metal reducing agent, the high-purity electrolyte solution for a vanadium redox flow battery (VRFB) according to the present invention eliminates the need for an additional electrolysis process; does not form toxic substances during a reaction process, and thus is environmentally friendly; and is electrochemically desirable under milder process conditions than that of an existing process. In addition, the VRFB comprising the electrolyte solution prepared according to the present invention may be used to expand the utility of new renewable energy through price reduction of large-capacity energy storage devices.

Systems and methods for operating an electric energy storage system are described. The systems and methods include ways of coupling electric energy storage cell stacks to an electric conductor or bus. The coupling is performed to reduce current flow through contactors and to increase a life span of the contactors.