Patent ID: 8852803

Claim:
A lithium secondary battery, comprising: a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material comprising a composite which comprises: a compound selected from the group consisting of a compound represented by Formula 1 below and a compound represented by Formula 2 below; a lanthanum oxide (La 2 O 3 ); and an oxide selected from the group consisting of a lanthanum zirconium oxide (La 2 Zr 2 O 7 ) and a lanthanum tantalum oxide (La 2 Ta 2 O 7 ): L 7+x M 3−x Zr 2 O 12 [Formula 1] wherein, in Formula 1, L is an alkali metal, M is a tri-valent metal, and x is a number of 0 to 3, and L 5+a M b Ta 2 O 12 [Formula 2] wherein, in Formula 2, L is an alkali metal, M is a tri-valent metal, a is a number that is greater than 0 and equal to or less than 3, and b is a number that is greater than 0 and equal to or less than 3; and a separator disposed between the positive electrode and the negative electrode.