A lithium-ion battery includes a cathode that includes an active cathode material. The active cathode material includes a cathode mixture that includes a lithium cobaltate and a manganate spinel a manganate spinel represented by an empirical formula of Li(1+x1)(Mn1−y1A′y2)2−x2Oz1. The lithium cobaltate and the manganate spinel are in a weight ratio of lithium cobaltate:manganate spinel between about 0.95:0.05 to about 0.55:0.45. A lithium-ion battery pack employs a cathode that includes an active cathode material as described above. A method of forming a lithium-ion battery includes the steps of forming an active cathode material as described above; forming a cathode electrode with the active cathode material; and forming an anode electrode in electrical contact with the cathode via an electrolyte.