Patent ID: 8026008

Claim:
A lithium secondary cell, comprising: 20 to 100 wt. % of lithium transition metal oxide represented by the following formula 1, relative to a total amount of a cathode active material, Li 1+z Ni b Mn c Me 1+(b+c) O 2 (1) wherein −0.5<z<0.5, 0.3<b<0.9, 0.1<c<0.8, b+c<1, Me is at least one element selected from a group consisting of Co, Al, Mg, Ti, Sr, Zn, B, Ca, Si, Ga, Sn, P, V, Sb, Nb, Ta, Mo, W, Zr, Y and Fe; and 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 protective film over the surface of the anode active material while inactivating impurities contained in the cathode active material are included in the electrolyte, wherein the second additive is a material having both at least one Si—O—Si bond and at least two carbon-carbon double bonds by reaction of impurities with water.