Lithium secondary battery of improved high-temperature cycle life characteristics

A lithium secondary battery comprising:

• (a) a cathode active material including a lithium-containing transition metal oxide having reversible lithium intercalation/deintercalation capacity, the lithium-containing transition metal oxide being at least one selected from the group consisting of LiCOaMnbNicMdO2 and LiXMn2-YM′YO4,
• wherein 0≦a≦1;
• 0≦b—1;
• 0≦d≦1, with the proviso that a+b+c+d=1;
• 0.9≦X≦2;
• 0≦Y≦0.5;
• M′ is selected from the group consisting of Al, B, Ga, Mg, Si, Ca, Ti, Zn, Ge, Y, Zr, Sn, Sr, Ba and Nb;
• and M′ is selected from the group consisting of Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge;
• (b) an anode active material including carbon-based material having reversible lithium intercalation/deintercalation capacity, the carbon-based material being graphitized carbon having a lattice spacing (d002) of less than 0.338 nm, as measured by X-ray diffraction, and a specific surface area of less than 10 m2/g, as measured by a BET method;
• (c) a porous separator;
• and
• (d) a non-aqueous electrolyte containing (i) a lithium salt, (ii) an electrolyte compound, and (iii) a compound of formula (I):
• wherein R1 is C1-C5 lower alkyl, and R2 is hydrogen or C1-C5 lower alkyl.