Patent ID: 8841026

Claim:
A cathode comprising: a current collector; a first cathode active material layer disposed on the current collector; and a second cathode active material layer disposed on a surface of the first cathode active material layer opposite the current collector, wherein the first cathode active material layer comprises a lithium transition metal oxide having a layered structure, and the second cathode active material layer comprises a lithium transition metal oxide having a spinel structure and an average working potential of 4.5 V or more, wherein the lithium transition metal oxide having the spinel structure is represented by Formula 2 below: Li 1+a Ni 0.5+b Mn 1.5+c M d O 4−e M′ e <Formula 2> in which −0.2≦a≦0.2, −0.2≦b≦0.2, −0.2≦c≦0.2, 0≦d≦0.5, and 0≦e≦0.1; M includes at least one metal selected from the group consisting of aluminum (Al), magnesium (Mg), titanium (Ti), zinc (Zr), vanadium (V), niobium (Nb), iron (Fe), zinc (Zn), silicon (Si), and tin (Sn); and M′ includes at least one element selected from the group consisting of nitrogen (N), sulfur (S), and fluorine (F), wherein the cathode has a coulombic efficiency of greater than 94% after 100 cycles when cycled at a temperature higher than 25° C., and wherein the lithium transition metal oxide of the second cathode active material layer is not charged or discharged during charging and discharging of the cathode.