Non-aqueous redox flow battery (RFB) comprising: a positive compartment in which a positive electrode is positioned and in which a positive non-aqueous liquid electrolyte is caused to flow; a negative compartment in which a negative electrode is positioned and in which a negative non-aqueous liquid electrolyte is caused to flow; an ion-exchange membrane positioned between the positive compartment and the negative compartment in which: said positive non-aqueous liquid electrolyte comprises a solution of copper triflate or tetrafluoroborate complexes [Cu(I) or Cu(II)] in at least one organic solvent; said negative non-aqueous liquid electrolyte comprises a solution of at least one benzothiadiazole or a derivative thereof in at least one organic solvent.