US Patent 8026008 Lithium secondary battery with improved cell characteristics

Disclosed herein is a lithium secondary cell including 20 to 100 wt. % of lithium transition metal oxide represented by a formula of Li1+zNibMncMe1−(b+c)O2, relative to a total amount of a cathode active material, as well as an electrolyte consisting of a lithium salt and a non-aqueous solvent, wherein a first additive to form a protective film (that is, a solid electrolyte interface film: SEI film) over a surface of an anode active material and a second additive to form another SEI film over the surface of the anode active material while inactivating impurities contained in the cathode active material are included in the electrolyte.