Aspects of the present invention relate to an electrolyte for a high voltage lithium rechargeable battery and a high voltage lithium rechargeable battery employing the electrolyte, and more particularly to an electrolyte for a high voltage lithium rechargeable battery comprising a non-aqueous organic solvent; a lithium salt; and a combination of a halogenated biphenyl and a dihalogenated toluene used as an additive where the combined additive has an oxidation reduction potential of 4.6 to 5.0 V with respect to lithium. The lithium rechargeable battery employing the electrolyte for a high voltage lithium rechargeable battery achieves overcharge stability.