Complex salts for use in eletrochemical cells

Complex salt of formula Mx+(EZ)y-x/y (I) is new. x, y = 1 - 6; Mx+ = metal ion; E = Lewis acid; and Z = e.g. OH E = BRRR, AlRRR, PRRRRR, AsRRRRR or VRRRRR; R - R may be bonded directly together by a single or double bond; R - R = (i) halogen; (ii) 1- 8 C alkyl or alkoxy optionally at least partly substituted by F, Cl or Br; (iii) optionally via oxygen bonded aromatic ring from phenyl, naphthyl, anthracenyl or phenanthrenyl optionally substituted up to 7 times by 1 - 8 C or F, Cl or Br; or (iv) optionally via oxygen bonded aromatic via heterocyclic rings from pyridyl, pyrazyl or pyrimidyl, optionally substituted by 1 - 8 C alkyl or F, Cl or Br; Z = OR, NRR, CRRR, OSO2R, N(SO2R)(SO2R), C(SO2R)(SO2R)(SO2R), OCOR; R - R = may be bonded directly together by single or double bonds, H or as for R - R. An Independent claim is also included for the use of (I) and mixtures thereof as conductive salts in electrochemical cells., preferably for batteries and supercapacitors.