NOVELTY - Redox flow battery electrolyte comprising preparing a basic electrolytic solution by adding and mixing vanadium compound containing vanadium (V) oxide, vanadium (III) oxide, vanadium (IV) oxide, ammonium metavanadate, reducing agent including hydrazine, oxalic acid, oxalic acid hydrate, sodium borohydride and sodium borohydride in an aqueous solution of sulfuric acid, adding the prepared basic electrolyte solution with a first additive including propylene carbonate and diethyl carbonate and 4-6 pts. wt. of second additive including phosphazene derivative, is claimed.    USE - The electrolyte is useful for a redox flow battery (claimed) for storing renewable energy such as wind and solar energy.    ADVANTAGE - The electrolyte stably maintains the electricity yield of the high-capacity redox flow battery, has high temperature, reduced inner resistance, improved conductivity, and corrosion resistance.    DETAILED DESCRIPTION - Redox flow battery electrolyte comprising preparing a basic electrolytic solution by adding and mixing vanadium compound containing vanadium (V) oxide, vanadium (III) oxide, vanadium (IV) oxide, ammonium metavanadate, purified starting material, reducing agent including hydrazine, oxalic acid, oxalic acid hydrate, sodiumborohydride and sodium borohydride in an aqueous solution of sulfuric acid and phosphoric acid in distilled water, adding the prepared basic electrolyte solution with 5-10 pts. wt. of a first additive including propylene carbonate and diethyl carbonate, and adding the prepared basic electrolyte solution with 4-6 pts. wt. of second additive including phosphazene derivative. An INDEPENDENT CLAIM is included for producing the redox flow battery electrolyte comprising 1M concentration of vanadyl sulfate, 3M concentration of sulfuric acid, 0.5M concentration of vanadium (V) oxide, 0.25M concentration of hydrazinemonohydrate to obtain a mixture solution, adding the mixture solution with 7.5 pts. wt. of the first additive and then mixing and stirring at room temperature, and adding the base electrolytic solution with 5 pts. wts. of the second additive and then mixing and stirring at room temperature.