In-situ electrolyte preparation in flow battery

A method of in-situ electrolyte preparation in a flow battery, the method comprising:

• (a) providing equal parts of a vanadium-based electrolyte solution having vanadium ions of predominantly vanadium V4+ to a first electrode and a second electrode of at least one cell of a flow battery, the second electrode being spaced apart from the first electrode, with an electrolyte separator layer arranged between the first electrode and the second electrode;
• (b) while the vanadium-based electrolyte solution is in the at least one cell of the flow battery, converting the vanadium V4+ in the vanadium-based electrolyte solution at the first electrode to vanadium V3+ and converting the vanadium V4+ in the vanadium-based electrolyte solution at the second electrode to vanadium V5+ by providing electrical energy through an electric circuit to the first electrode and the second electrode;
• (c) after said step (b), while the vanadium-based electrolyte solution is in the at least one cell of the flow battery, providing a reducing agent to the vanadium-based electrolyte solution of the second electrolyte to reduce the vanadium V5+ to vanadium V4+;
• and
• (d) after said step (c), while the vanadium-based electrolyte solution is in the at least one cell of the flow battery, establishing the flow battery to be in a fully charged state by converting the vanadium V3+ of said step (b) in the vanadium-based electrolyte solution at the first electrode to vanadium V2+ and converting the vanadium V4+ of said step (c) in the vanadium-based electrolyte solution at the second electrode to vanadium V5+ by providing electrical energy through the electric circuit to the first electrode and the second electrode.