TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The organic phosphate compound is of formula (R1O-P(=O)(OR2)-OR3) (I), preferably trimethyl phosphate, triethyl phosphate, tri-n-propyl phosphate, triisopropyl phosphate, tri-n-butyl phosphate, triisobutyl phosphate, tri-tert-butyl phosphate, triallyl phosphate, tribenzyl phosphate or triphenyl phosphate.R1-R3 = 1-8C alkyl, 2-8C alkenyl, 2-8C alkynyl, 3-8C cycloalkyl, 6-12C aryl, 6-12C arylalkyl or 2-8C acyl.The metal is nickel, cobalt, iron, ruthenium, zinc, manganese, yttrium, zirconium, titanium, chromium, magnesium, cerium, copper, lead or vanadium. In the metal-ligand coordination compound, 3-6 equivalents of the ligand are bound to the metal. An oxidation-reduction reaction of the metal-ligand coordination compound is reversible. The metal-ligand coordination compound is iron(II) methoxy-phosphates of formula (II)-(V) or nickel(II) methoxy-phosphate of formula (VI). The organic electrolyte solution further comprises: tetrafluoroborate, hexafluorophosphate, perchlorate, trifluoromethanesulfonate or bis(trifluoromethylsulfonyl)amide as a counter anion of the metal-ligand coordination compound; and a supporting electrolyte. The supporting electrolyte is at least one of lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethylsulfonyl)amide, lithium perfluorobutane sulfonate, lithium aluminate, lithium aluminum chloride, lithium sulfonamide of formula (LiN(CxF2x+1SO2)(CyF2y+1SO2)), sodium tetrafluoroborate, sodium hexafluorophosphate, sodium sulfate, tetraethylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, tetraethylammonium tetrafluoroborate, or tetrabutylammonium tetrafluoroborate.x, y = natural numbers.The metal-ligand coordination compound is an ionic liquid and is dissolved in a solvent which is a non-aqueous solvent. The catholyte and the anolyte comprise a redox couple of iron2+/nickel0. The redox flow battery further comprises a catholyte tank and an anolyte tank respectively connected to the cathode cell and the anode cell to transfer a fluid. The ion exchange membrane is an anion exchange membrane.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The non-aqueous solvent is at least one of diethyl carbonate, dimethyl carbonate, dipropyl carbonate, acetonitrile, gamma -butyrolactone, propylene carbonate, ethylene carbonate, butylene carbonate, N-methyl-2-pyrrolidone, fluoroethylene carbonate, N,N-dimethylformamide, dimethylsulfoxide, dichloromethane, chloroform, benzene, toluene, xylene, chlorobenzene, methyl acetate, ethyl acetate, acetone, methyl ethyl ketone, cyclohexanone, diethyl ether, 1,2-dimethoxyethane, tetrahydrofuran, 1,4-dioxane, methanol, ethanol or N,N-dimethylacetamide. EXAMPLE - 3 g Of an ivory-colored solid of iron(II) tetrafluoroborate hexahydrate was added to a round-bottom flask. An argon line was connected to the round-bottom flask to form an argon atmosphere in the flask, and then, 3 equivalents of trimethyl phosphate were added into the flask using a syringe. After installing a reflux condenser in the round-bottom flask, the reaction mixture was stirred with a magnetic stirrer under an argon atmosphere at a temperature of 140 degrees C using an oil bath. The reaction mixture became an ivory-colored liquid with high viscosity during the reaction process. After about an hour, color of the entire liquid was changed to orange, and when the color change was observed, the reaction was terminated and the temperature of the liquid was lowered to room temperature. Thus organic electrolyte solution of iron tetrafluoroborate-tris(trimethyl phosphate) hexahydrate was obtained.