The effort to develop improved electrolytes which satisfy the requirements of a high voltage lithium rechargeable battery has prompted the search for new conductive salts which are thermally and electrochemically stable. We have identified a ternary solvent mixture containing the electrolyte lithium tris(trifluoromethanesulfonyl)methide, LiC(CF3SO2)(3), that is conductive and electrochemically stable at cell potentials exceeding 4.0 V. Ionic conductivities were measured between -30 and 55 degrees C, and electrochemical stability determined by cyclic voltammetry on glassy carbon, platinum, and aluminum substrates.