Redox flow battery with electrolyte balancing and compatibility enabling features

A redox flow battery comprising:

• first and second cells, each said cell having first and second electrodes and a separator layer arranged between the first and second electrodes;
• a first circulation loop fluidly connected with the first electrode of the first cell;
• a polysulfide electrolyte solution having a pH 11.5 or greater contained in the first recirculation loop;
• a second circulation loop fluidly connected with the second electrode of the second cell;
• an iron electrolyte solution having a pH 3 or less contained in the second circulation loop;
• a third circulation loop fluidly connected with the second electrode of the first cell and the first electrode of the second cell;
• and
• an intermediator electrolyte solution contained in the third circulation loop,
• wherein the polysulfide electrolyte solution and the intermediator electrolyte solution in the first cell, and the iron electrolyte solution and the intermediator electrolyte solution in the second cell, are operable to undergo reversible reactions to store input electrical energy upon charging and discharge the stored electrical energy upon discharging.