The invention relates to
electrolyte salts for electrochemical devices of improved physical, chemical and electrochemical stability. The improvement resides in the use of anions of salts of the formula comprising: i) (B12FxZ12-x)2− wherein Z comprises at least one of H, Cl, Br or OR; R comprises at least one of H,
alkyl or fluoroalkyl, or at least one
polymer and x is at least 3 on an average basis but not more than 12; ii) ((R′R″R′″)NB12FxZ(11-x))−, wherein N is bonded to B and each of R′, R″, R′″ comprise a member independently selected from the group consisting of
hydrogen,
alkyl, cycloalkyl,
aryl and a
polymer; Z comprises H, Cl, Br, or OR, where R comprises H,
alkyl or perfluoroalkyl or a
polymer, and x is an integer from 0 to 11; or iii) (R″″CB11FxZ(11-x))−, wherein R″″ is bonded to C and comprises a member selected from the group consisting of
hydrogen, alkyl, cycloalkyl,
aryl, and a polymer, Z comprises H, Cl, Br, or OR, wherein R comprises H, alkyl or perfluoroalkyl or a polymer, and x is an integer from 0 to 11.