[Problem to be Solved] To provide a vanadium active material solution which has a vanadium active material concentration of 2.5 M or more in a sulfuric acid solution including a dispersoid (suspensible material), can stably maintain high energy density based on the concentration, and can respond also to fast charge and discharge, and to provide a vanadium redox battery using the active material solution.

[Solution] The above problem is solved by a vanadium active material solution comprising a vanadium compound, which is an active material, as a solute and a dispersoid, wherein the total concentration of vanadium is 2.5 M or more. Here, in a negative electrolyte, the vanadium compound comprises one or both of bivalent and trivalent vanadium. In a positive electrolyte, the vanadium compound comprises one or both of quadrivalent and pentavalent vanadium. In an active material solution, the vanadium compound comprises one or both of trivalent and quadrivalent vanadium. The average diameter of the dispersoid is in the range of 1 nm or more and 100 μm or less.

According to one embodiment of the present invention, the method for controlling the pump speed of a redox flow battery for transferring an electrolyte stored in an electrolyte tank to a cell stack comprises the steps of: measuring the input power and/or the output power of the redox flow battery; measuring the charging power and/or the discharging power of the redox flow battery; calculating the power loss of the redox flow battery by using the difference between the input power and the charging power, or the difference between the output power and the discharging power; and adjusting the pump speed according to the power loss.

The present specification relates to a novel compound, a polymer electrolyte membrane including the same, a membrane-electrode assembly including the polymer electrolyte membrane, a fuel cell including the membrane-electrode assembly, and a redox flow battery including the polymer electrolyte membrane.

The present specification relates to a polymer electrolyte membrane, an electrochemical battery including the polymer electrolyte membrane, an electrochemical battery module including the electrochemical battery, a flow battery including the polymer electrolyte membrane, a method for manufacturing a polymer electrolyte membrane, and an electrolyte solution for a flow battery.

A conductive nanoporous membrane system has a first ion exchange membrane formed from a nanoporous substrate that is coated with a metal or carbon or conductive polymers to form a conductive membrane, a second ion exchange membrane that is also formed from a nanoporous substrate coated with a metal to form a conductive membrane is positioned in spaced relation to the first conductive membrane and coupled to a voltage source; the negatively potential membrane acts as a cation exchange membrane in the presence of an electrolyte, and the positively connected electrode behave as anodic exchange membrane in the presence of an electrolyte due to the formation of electrical double layers at the interface between metal and liquid electrolyte.

Electrochemical cells, such as those present within flow batteries, can have at least one electrode with a density gradient in which the density increases outwardly from a separator. Such electrodes can decrease contact resistance and lessen the incidence of parasitic reactions in the electrochemical cell. Flow batteries containing the electrochemical cells can include: a first half-cell containing a first electrode, a second half-cell containing a second electrode, and a separator disposed between the first half-cell and the second half-cell. At least one of the first electrode and the second electrode has a density gradient such that a density of at least one of the first electrode and the second electrode increases outwardly from the separator.

The present invention relates to use of a quaternary ammonium salt-type anthraquinone-based active material, and a salt cavern organic aqueous redox flow battery. The quaternary ammonium salt-type anthraquinone-based active material is used as a negative active material in a salt cavern battery, and a quaternary ammonium salt group is introduced, which can improve the solubility of anthraquinone in a neutral sodium chloride solution, thereby increasing the energy density of the battery. Also, the material has a relatively good stability, without the need for charging and discharging under the protection of an inert gas environment.

Intermittent energy sources, including solar and wind, require scalable, low-cost, multi-hour energy storage solutions to be effectively incorporated into the grid. Redox-flow batteries offer a solution, but suffer from rapid capacity fade and low Coulombic efficiency due to the high permeability of redox-active species across the battery's membrane. Here we show that active-species crossover can be arrested by scaling the membrane's pore size to molecular dimensions and in turn increasing the size of the active material to be above the membrane's pore-size exclusion limit. When oligomeric redox-active organic molecules were paired with microporous polymer membranes, the rate of active-material crossover was either completely blocked or slowed more than 9,000-fold compared to traditional separators at minimal cost to ionic conductivity. In the case of the latter, this corresponds to an absolute rate of ROM crossover of less than 3 μmol cm.sup.−2 day.sup.−1 (for a 1.0 M concentration gradient), which exceeds performance targets recently set forth by the battery industry. This strategy was generalizable to both high and low-potential ROMs in a variety of electrolytes, highlighting the importance of macromolecular design in implementing next-generation redox-flow batteries.

Methods and systems are provided for a redox flow battery system. In one example, the redox flow battery system includes a cell stack compressed between terminal structures defining ends of the redox flow battery. The cell stack may be formed of a plurality of cells where each cell includes a deformable positive electrode in contact with a first face of a membrane separator and a negative electrode configured to be less compressible than the positive electrode and arranged at a second face of the membrane separator.

The present disclosure relates to electrodes comprising a polymer film and a substrate, wherein the polymer film has a thickness of about 5 nm to about 600 nm. The present disclosure also relates to electrochemical cells and batteries comprising the electrodes disclosed herein. The present disclosure also relates to methods of making the electrodes disclosed herein.