Aqueous electrolytes comprising fluorenone/fluorenol derivatives are disclosed. The electrolyte may be an anolyte for an aqueous redox flow battery. In some embodiments, the compound, or salt thereof, has a structure according to any one of formulas I-III ##STR00001##
where Q.sup.1-Q.sup.4 independently are CH, C(R.sup.1) or N, wherein 0, 1, or 2 of Q.sup.1-Q.sup.4 are N; Q.sup.5-Q.sup.8 independently are CH, C(R.sup.2), or N, wherein 0, 1, or 2 of Q.sup.5-Q.sup.8 are N; Y is C═O or C(H)OH; R.sup.1 and R.sup.2 independently are an electron withdrawing group; n is an integer >1; and x and y independently are 0, 1, 2, 3, or 4, where at least one of x and y is not 0.

A production method includes: an alkali extraction step of adding an alkali and water, or an alkali solution, to raw material ash containing an ammonium sulfate component, sulfuric acid, vanadium, and at least one other metal selected from nickel, iron, and magnesium, wherein a pH of 13 or higher is achieved, to obtain an alkali leachate; a solid-liquid separation step on the alkali leachate to obtain a leach filtrate containing vanadium; an evaporation concentration step of evaporating and concentrating the leach filtrate to obtain a concentrated liquid; and a crystallization/solid-liquid separation step of cooling and crystalizing the concentrated liquid and recovering a precipitate containing a vanadium compound. Another production method includes an alkali extraction step, a solid-liquid separation step, an evaporation concentration step, an alkali concentration adjustment step of further adding an alkali or alkali solution to a concentrated liquid to obtain a concentration-adjusted liquid, and a crystallization/solid-liquid separation step.

A separator plate for an electrochemical system, comprising a first and a second metal layer arranged with flat sides adjacent to each other. The first and the second metal layer each having at least one through-opening for supplying and/or discharging a fluid. Circumferential edges of the through-openings are formed at least in part by a half-bead. An open edge of the half-bead is angled so as to form a collar.

A redox battery comprises a plurality of redox battery cells stacked in a stacking direction, wherein each of the redox battery cells comprises a first half cell connected to a positive current collector, a second half cell connected to a negative current collector and an ion exchange membrane separating the first and second half cells. The redox battery additionally comprises a positive conducting bus bar extending in the stacking direction and electrically connecting the positive current collectors of the redox battery cells in parallel, and a negative conducting bus bar extending in the stacking direction and electrically connecting the negative current collectors of the redox battery cells in parallel. One or both of the positive and negative bus bars are configured as fastening means for mechanically fastening the stacked redox battery cells in the stacking direction

Provided are an ion exchange membrane that has excellent mechanical strength as well as can exhibit an excellent proton conductivity over a long period, a membrane electrode assembly, a fuel cell, a redox flow secondary battery, a water electrolyzer, and an electrolyzer for organic hydride synthesis.

An ion exchange membrane containing:

an electrolyte containing a perfluorocarbon sulfonic acid polymer; and

glass fiber having a SiO.sub.2 content of 99.9% by mass or more.

Pyridinium derivatives, methods of making the pyridinium derivatives, and electrochemical cells that use the pyridinium derivatives as anolytes are provided. The pyridinium derivatives have a redox core with two or more pyridinium groups and substituents at pyridinium ring nitrogen atoms. The pyridinium derivatives can be made by reacting pyridyl reactant molecules having two or more pyridyl groups with water-soluble derivatizing reactant molecules via a hydrothermal synthesis.

Systems and methods are provided for assembling and operating an electrode assembly for a redox flow battery system. In one example, the electrode assembly may include an inflatable housing in which a negative electrode spacer and a positive electrode may be positioned, wherein the inflatable housing may inflate responsive to applied internal pressure during operation of the redox flow battery system. In some examples, the electrode assembly may be assembled via roll-to-roll processing and may be mechanically and fluidically coupled to electrode assemblies of like configuration. In this way, tolerance stacking may be decreased, processing may be simplified, and costs may be reduced relative to molding-based processes for electrode assembly manufacturing.

A controller stops flow of posolyte through a positive electrode chamber of a flow cell to trap the posolyte within the positive electrode chamber and hydraulically isolate the flow cell without stopping flow of negolyte through a negative electrode chamber of the flow cell, discharges the flow cell until hydrogen gas is evolved at a reactive surface of the positive electrode chamber while the posolyte is trapped within the positive electrode chamber, and subsequently discontinues the discharge and restarts the flow of the posolyte through the positive electrode chamber.

A redox flow battery and battery system are provided. In one example, the redox flow battery includes a set of pressure plates having a first pressure plate at a first terminal end and a second pressure plate at a second terminal end, the second terminal end and the first terminal end positioned on opposing longitudinal sides of the redox flow battery. The redox flow battery further includes a first cell stack positioned longitudinally between the first pressure plate and the second pressure plate, each of the first and second pressure plates includes a plurality stacking detents on a first flange and a plurality of stacking protrusions on a second flange, and the first flange and the second flange arranged on opposing vertical sides of the redox flow battery.

Disclosed is an aqueous electrolyte for redox flow battery, including a compound of formula (I)

##STR00001##

and/or an ion of compound (I), and/or a salt of compound (I), and/or a reduced form of the anthraquinone member of compound (I), wherein: X.sup.1, X.sup.2, X.sup.4, X.sup.5, X.sup.6, X.sup.7 and X.sup.8 are independently selected from the group consisting of a hydrogen atom, a linear, cyclic or branched, saturated or unsaturated, optionally substituted, hydrocarbon group including from 1 to 10 carbon atoms, a OH group and a —O-A-R.sup.1 group, A representing a linear, cyclic or branched, saturated or unsaturated, optionally substituted, hydrocarbon group including from 1 to 10 carbon atoms; R.sup.1 representing COOH or SO.sub.3H; wherein one and only one of X.sup.1, X.sup.2, X.sup.4, X.sup.5, X.sup.6, X.sup.7 and X.sup.8 is OH, and wherein one and only one of X.sup.1, X.sup.2, X.sup.4, X.sup.5, X.sup.6, X.sup.7 and X.sup.8 is —O-A-R.sup.1.