An electrolyte solution comprising: - a compound of formula wherein M 101 is P or P=O; R 101 each independently is C 1-11 -alkyloxy, silyloxy, C 1-11 -alkylsilyloxy, C 1-11 -alkoxysilyloxy or C 6-18 -arylsilyloxy; n 101 is the number of R 101 s binding to M 101 , and is the oxidation number of M 101 minus 1 or the oxidation number of M 101 minus 3; and R 102 -R 104 each independently are C 1-11 -alkyl, C 2-11 -alkenyl, C 1-11 -alkyloxy or C 6-11 -aryl, - at least one compound selected from the formulae (11-1) to (11-4): wherein R 111 and R 112 each independently are H, F or optionally fluorinated alkyl; and R 113 is fluorine-free alkyl or an organic group containing an unsaturated carbon-carbon bond; wherein R 121 is C 1-7 -alkyl, C 2-8 -alkenyl, C 2-9 -alkynyl or C 6-12 -aryl, each optionally fluorinated, and each optionally containing at least one of O, Si, S and N in the structure; wherein R 131 and R 132 are (i) each individually H, F, or C 1-7 -alkyl, C 2-7 -alkenyl, C 2-9 -alkynyl or C 5-12 -aryl, each optionally fluorinated, or (ii) hydrocarbon groups binding to each other to form a 5- or 6-membered hetero ring with a nitrogen atom; and R 131 and R 132 each optionally contain at least one of O, S, and N in the structure, wherein Rf 141 is CF 3 -, CF 2 H-, or CFH 2 -; and R 141 is C 2-5 -alkenyl or C 2-8 -alkynyl, each optionally fluorinated, and optionally contains Si in the structure. - a compound of formula wherein M 101 is P or P=O; R 101 each independently is C 1-11 -alkyloxy, silyloxy, C 1-11 -alkylsilyloxy, C 1-11 -alkoxysilyloxy or C 6-18 -arylsilyloxy; n 101 is the number of R 101 s binding to M 101 , and is the oxidation number of M 101 minus 1 or the oxidation number of M 101 minus 3; and R 102 -R 104 each independently are C 1-11 -alkyl, C 2-11 -alkenyl, C 1-11 -alkyloxy or C 6-11 -aryl, M 101 is P or P=O; R 101 each independently is C 1-11 -alkyloxy, silyloxy, C 1-11 -alkylsilyloxy, C 1-11 -alkoxysilyloxy or C 6-18 -arylsilyloxy; n 101 is the number of R 101 s binding to M 101 , and is the oxidation number of M 101 minus 1 or the oxidation number of M 101 minus 3; and R 102 -R 104 each independently are C 1-11 -alkyl, C 2-11 -alkenyl, C 1-11 -alkyloxy or C 6-11 -aryl, - at least one compound selected from the formulae (11-1) to (11-4): wherein R 111 and R 112 each independently are H, F or optionally fluorinated alkyl; and R 113 is fluorine-free alkyl or an organic group containing an unsaturated carbon-carbon bond; wherein R 121 is C 1-7 -alkyl, C 2-8 -alkenyl, C 2-9 -alkynyl or C 6-12 -aryl, each optionally fluorinated, and each optionally containing at least one of O, Si, S and N in the structure; wherein R 131 and R 132 are (i) each individually H, F, or C 1-7 -alkyl, C 2-7 -alkenyl, C 2-9 -alkynyl or C 5-12 -aryl, each optionally fluorinated, or (ii) hydrocarbon groups binding to each other to form a 5- or 6-membered hetero ring with a nitrogen atom; and R 131 and R 132 each optionally contain at least one of O, S, and N in the structure, wherein Rf 141 is CF 3 -, CF 2 H-, or CFH 2 -; and R 141 is C 2-5 -alkenyl or C 2-8 -alkynyl, each optionally fluorinated, and optionally contains Si in the structure. (i) each individually H, F, or C 1-7 -alkyl, C 2-7 -alkenyl, C 2-9 -alkynyl or C 5-12 -aryl, each optionally fluorinated, or (ii) hydrocarbon groups binding to each other to form a 5- or 6-membered hetero ring with a nitrogen atom; <EOS>