Solvents and novel electrolytic compositions having a large range of stability and high conductivity

An aprotic polar compound having solvent properties, and of the general formula:

• R1R2NX(Z)R7
• wherein
• X=C or SO;
• Z=O, NSO2NR3R4 or NCN;
• R1 et R2 are the same or different and are C1-18alkyl, C1-18 oxaalkyl, C1-18 alkylene or C1-18oxaalkylene;
• R3 à R6 are the same or different and are C1-18alkyl or C1-18 oxaalkyl;
• R7 is RF, RFCH2O—, (RF)2CHO—, (RFCH2)2N— or NR5R6;
• RF is a fluorine atom, C1-4alkyl, C1-4oxaalkyl C1-4azaalkyl,
• with the proviso that:
• 1) if Z=O, then RF is not C1-4alkyl;
• and
• 2) if Z=O and X=SO, then R5 or R6 is not is not C1-4alkyl or C1-4oxaalkyl.