An efficient preparation of new fluorinated lithium and ammonium sulfonimides, from the corresponding sulfonyl fluorides, is reported. These sulfonyl fluorides are reacted with benzylamine, then triflated. Due to the high leaving ability of fluorinated sulfonimides, the formed N-benzylsulfonimides are simply debenzylated with an alcohol. Finally, the intermediate oxonium sulfonimides are neutralized, in situ, by various bases. The obtained sulfonimides are potential electrolytes for lithium batteries or fuel cells.