Secondary battery having improved safety

A secondary battery comprising an electrode assembly including a cathode, an anode, a separator interposed between the cathode and the anode and an electrolyte, the secondary battery comprising a HF scavenger in the electrolyte,

• wherein the cathode comprises lithium manganese composite oxide with a spinel structure represented by the following Formula 2 as a cathode active material:
• LixNiyMn2-yO4 (2)
• wherein 0.9≦x≦1.2 and 0.4≦y≦0.5;
• wherein the anode comprises lithium titanium oxide (LTO) represented by Formula 4:
• LiaTibO4 (4)
• wherein 0.5≦a≦3 and 1≦b≦2.5;
• and
• wherein the HF scavenger is contained in the electrolyte in an amount of 0.1% to 10%, based on the total weight of the electrolyte.