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 selected from benzothiadiazoles having general formula (I): in which R 1 , R 2 , R 3 and R 4 , mutually identical or different, represent a hydrogen atom, or a halogen atom such as chlorine, fluorine, bromine, iodine, preferably fluorine; or represent one of the following groups: -CN, -NO 2 , -COOH, -SO 3 H,-SH; or are selected from: linear or branched, saturated or unsaturated C 1 -C 10 , preferably C 1 -C 4 , alkyl groups, linear or branched, saturated or unsaturated C 1 -C 10 , preferably C 1 -C 4 , alkoxy groups, carboxylic esters having general formula R'-COO-R" in which R' and R", mutually identical or different, are selected from linear or branched, saturated or unsaturated C 1 -C 10 , preferably C 1 -C 4 , alkyl groups, sulfonic esters having general formula R'-OSO 2 -R" in which R' and R" have the same meanings described above, thioesters having general formula R'-SO-R" in which R' and R" have the same meanings described above, -(O-CH 2 -CH 2 ) n -OH groups in which n is an integer ranging from 1 to 4, -(O-CH(CH 3 )-CH 2 ) n -OH groups in which n is an integer ranging from 1 to 4, optionally substituted aryl groups, optionally substituted heteroaryl groups in at least one organic solvent. - 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 - 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 selected from benzothiadiazoles having general formula (I): in which R 1 , R 2 , R 3 and R 4 , mutually identical or different, represent a hydrogen atom, or a halogen atom such as chlorine, fluorine, bromine, iodine, preferably fluorine; or represent one of the following groups: -CN, -NO 2 , -COOH, -SO 3 H,-SH; or are selected from: linear or branched, saturated or unsaturated C 1 -C 10 , preferably C 1 -C 4 , alkyl groups, linear or branched, saturated or unsaturated C 1 -C 10 , preferably C 1 -C 4 , alkoxy groups, carboxylic esters having general formula R'-COO-R" in which R' and R", mutually identical or different, are selected from linear or branched, saturated or unsaturated C 1 -C 10 , preferably C 1 -C 4 , alkyl groups, sulfonic esters having general formula R'-OSO 2 -R" in which R' and R" have the same meanings described above, thioesters having general formula R'-SO-R" in which R' and R" have the same meanings described above, -(O-CH 2 -CH 2 ) n -OH groups in which n is an integer ranging from 1 to 4, -(O-CH(CH 3 )-CH 2 ) n -OH groups in which n is an integer ranging from 1 to 4, optionally substituted aryl groups, optionally substituted heteroaryl groups in at least one organic solvent. <EOS>