NOVELTY - A secondary battery (10) has an anode active material, an anode collector (11) which carries out oxidation reduction of anode active material in an electrolyte, a cathode active material, a cathode collector (12) which carries out oxidation reduction of cathode active material in electrolyte, and an isolation unit (13) having ionic conductivity, which separates anode active material and cathode active material. The anode active material and/or cathode active material is an organic compound having thiol group or an organic compound having specific structure.    USE - For power supply system (claimed) used in electric vehicles.    ADVANTAGE - The secondary battery has excellent durability and safety and provides compact power supply system having favorable mounting property to electronic device.    DETAILED DESCRIPTION - A secondary battery (10) has an anode active material, an anode collector (11) which carries out oxidation reduction of anode active material in an electrolyte, a cathode active material, a cathode collector (12) which carries out oxidation reduction of cathode active material in electrolyte, and an isolation unit (13) having ionic conductivity, which separates anode active material and cathode active material. The anode active material and/or cathode active material is an organic compound having a thiol group or an organic compound having at least one structure of formulae (1)-(5):    X1=nitrogen or carbon atom;    R1-R4=H, hydroxyl, cyano, amino, nitro, nitroso or (un)saturated linear or cyclic aliphatic group;    R5-R8=linear or branched (un)saturated aliphatic group containing halogen, oxygen, nitrogen, sulfur, silicon, phosphorus or boron atom;    X2=sulfur or oxygen atom;    X3=sulfur, oxygen, carbon or tellurium atom;and    X4=H, cyano, halogen atom, or linear or branched (un)saturated aliphatic group with oxygen atom bonded at para position or ortho position of six-membered ring.    INDEPENDENT CLAIMS are included for the following:    (a) power supply system; and    (b) usage of the power supply system.    DESCRIPTION OF DRAWING(S) - The figure shows the schematic block diagram of the redox flow battery.    Redox flow battery (10)    Anode collector (11)    Cathode collector (12)    Isolation unit (13)    Container (14)