TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The concentration of titanium ion in the positive electrode electrolyte solution is 50% or more of the concentration of manganese ion in positive electrode electrolyte solution. The concentration of manganese ion and titanium ion in positive electrode electrolyte solution and negative electrode electrolyte solution is similar. The concentration of the manganese ion and titanium ion is 0.3-5 M. The two-poles electrolyte solution of the positive electrode electrolyte solution and the negative electrode electrolyte solution contains a sulfate anion. The concentration of sulfuric acid in two-poles electrolyte solution is less than 5 M, preferably 1-3 M. The concentration of manganese ion in two-poles electrolyte solution is 0.5-1.5 M. The concentration of the titanium ion in two-poles electrolyte solution is 0.5-1.5 M. The positive electrode electrolyte solution contains bivalent manganese ion, trivalent manganese ion, and tetravalent titanium ion. The negative electrode electrolyte solution contains trivalent titanium ion, tetravalent titanium ion, and bivalent manganese ion. The positive electrode electrolyte solution contains bivalent manganese ion, trivalent manganese ion, tetravalent manganese ion, and tetravalent titanium ion. The negative electrode electrolyte solution contains bivalent titanium ion, trivalent titanium ion, tetravalent titanium ion, and bivalent manganese ion. The positive electrode and the negative electrode contains metal chosen from ruthenium, titanium, iridium, manganese, palladium, gold and/or platinum, composite material containing oxide of metal chosen from ruthenium, titanium, iridium, manganese, palladium, gold and/or platinum, carbon composite containing the composite material, and dimentional stable electrode containing the composite material, conductive polymer, graphite, glassy carbon, conductive diamond, electroconductive diamond-like carbon, nonwoven fabric containing carbon fibers and material chosen from woven fabric which consists of carbon fibers. The solvent of the two-poles electrolyte solution of the positive electrode electrolyte solution and the negative electrode electrolyte solution is chosen from aqueous solution of sulfuric acid, potassium sulfate, sodium sulfate, phosphoric acid, potassium phosphate, sodium phosphate, pyrophosphoric acid, nitric acid, potassium nitrate and sodium nitrate.