Rechargeable battery cell (2, 20, 40, 101) containing an active metal, at least one positive electrode (4, 23, 44), at least one negative electrode (5, 22, 45), a housing (1, 28, 102) and an electrolyte, wherein the active metal is sodium, and wherein the electrolyte is based on SO 2 and contains at least a first conducting salt which has the formula, wherein - the substituents R 1, R 2 and R 3 are independently selected from the group consisting of a halogen atom, a hydroxy group and a chemical group -OR 5; the substituent R 4 is selected from the group consisting of a hydroxy group and a chemical group -OR 5; - the substituent R 5 is selected from the group consisting of C 1 -C 10 alkyl, C 2 -C 10 alkenyl, C 2 -C 10 alkynyl, C 3 -C 10 cycloalkyl, C 6 -C 14 aryl and C 5- C 14 heteroaryl, wherein the aliphatic, cyclic, aromatic and heteroaromatic groups may be unsubstituted or substituted; - Z is aluminium or boron; - at least two of the substituents R 1, R 2, R 3 and R 4 may together form a chelating ligand which is coordinated to Z; and - the aliphatic, cyclic, aromatic and heteroaromatic groups of the substituent R 5 can be further substituted with one or more halogen atoms, in particular fluorine, or a chemical group selected from the group consisting of C 1 -C 4 alkyl, C 2 -C 4 alkenyl, C 2 -C 4 alkynyl, phenyl, benzyl, and fully or partially halogenated, in particular fully or partially fluorinated C 1 -C 4 alkyl, C 2 -C 4 alkenyl, C 2 -C 4 alkynyl, phenyl and benzyl. and wherein the electrolyte is based on SO 2 and contains at least a first conducting salt which has the formula, wherein - the substituents R 1, R 2 and R 3 are independently selected from the group consisting of a halogen atom, a hydroxy group and a chemical group -OR 5; the substituent R 4 is selected from the group consisting of a hydroxy group and a chemical group -OR 5; - the substituent R 5 is selected from the group consisting of C 1 -C 10 alkyl, C 2 -C 10 alkenyl, C 2 -C 10 alkynyl, C 3 -C 10 cycloalkyl, C 6 -C 14 aryl and C 5- C 14 heteroaryl, wherein the aliphatic, cyclic, aromatic and heteroaromatic groups may be unsubstituted or substituted; - Z is aluminium or boron; - at least two of the substituents R 1, R 2, R 3 and R 4 may together form a chelating ligand which is coordinated to Z; and - the aliphatic, cyclic, aromatic and heteroaromatic groups of the substituent R 5 can be further substituted with one or more halogen atoms, in particular fluorine, or a chemical group selected from the group consisting of C 1 -C 4 alkyl, C 2 -C 4 alkenyl, C 2 -C 4 alkynyl, phenyl, benzyl, and fully or partially halogenated, in particular fully or partially fluorinated C 1 -C 4 alkyl, C 2 -C 4 alkenyl, C 2 -C 4 alkynyl, phenyl and benzyl. - the substituents R 1, R 2 and R 3 are independently selected from the group consisting of a halogen atom, a hydroxy group and a chemical group -OR 5; the substituent R 4 is selected from the group consisting of a hydroxy group and a chemical group -OR 5; - the substituent R 5 is selected from the group consisting of C 1 -C 10 alkyl, C 2 -C 10 alkenyl, C 2 -C 10 alkynyl, C 3 -C 10 cycloalkyl, C 6 -C 14 aryl and C 5- C 14 heteroaryl, wherein the aliphatic, cyclic, aromatic and heteroaromatic groups may be unsubstituted or substituted; - Z is aluminium or boron; - at least two of the substituents R 1, R 2, R 3 and R 4 may together form a chelating ligand which is coordinated to Z; and - the aliphatic, cyclic, aromatic and heteroaromatic groups of the substituent R 5 can be further substituted with one or more halogen atoms, in particular fluorine, or a chemical group selected from the group consisting of C 1 -C 4 alkyl, C 2 -C 4 alkenyl, C 2 -C 4 alkynyl, phenyl, benzyl, and fully or partially halogenated, in particular fully or partially fluorinated C 1 -C 4 alkyl, C 2 -C 4 alkenyl, C 2 -C 4 alkynyl, phenyl and benzyl.