Patent ID: 8632918

Claim:
A non-aqueous rechargeable electrochemical cell comprising: a positive electrode; a negative electrode; a separator interposed between said positive electrode and said negative electrode; and a non-aqueous electrolyte in simultaneous contact with said positive electrode, said negative electrode and said separator, said electrolyte consisting essentially of: a lithium salt of bis(oxalato)borate (LiBOB) dissolved in an at least 50 weight percent gamma-butyrolactone and an at least 5 weight percent but less than 50 weight percent of a non-aqueous lactone solvent selected from the group consisting of: beta-propiolactone, beta-butyrolactone, alpha-methyl-gamma-butyrolactone, gamma-valerolactone, delta-valerolactone, gamma-caprolactone, epsilon-caprolactone, gamma-octanolactone, gamma-nanolactone, gamma-decanolactone, delta-decanolactone, gamma-undecanolactone, delta-undecanolactone, and delta-dodecanolactone, whose structure can be represented by the general formula: where R 1 -R 6 are independently in each occurrence a hydrogen radical; an aliphatic moiety containing 1 to 5 carbon atoms, or an aromatic moiety containing 6 to 24 carbon atoms; n is an integer between 0 and 4 inclusive with the proviso when all R 1 -R 6 are hydrogen radicals, n is not 1 and a second solvent component limited to 5 to 45 weight percent of the compounds selected from any other lactone solvents each weight less the weight of said lithium salt.