A method for producing electric power and regenerating an aqueous multi-electron oxidant (AMO) and a reducer in an energy storage cycle is provided. A discharge system includes a discharge unit, an acidification reactor, and a neutralization reactor. The acidification reactor converts an oxidant fluid including the AMO into an acidic oxidant fluid. The discharge unit generates electric power and a discharge fluid by transferring electrons from a positive electrode of an electrolyte-electrode assembly (EEA) to the AMO and from a reducer to a negative electrode of the EEA. The neutralization reactor neutralizes the discharge fluid to produce a neutral discharge fluid. The regeneration system splits an alkaline discharge fluid into a reducer and an intermediate oxidant in a splitting-disproportionation reactor and releases the reducer and a base, while producing the AMO by disproportionating the intermediate oxidant. The regenerated AMO and reducer are supplied to the discharge unit for power generation.