LITHIUM-ION SECONDARY BATTERY

In one embodiment, an active cathode material comprises a mixture that includes: at least one of a lithium cobaltate and a lithium nickelate; and at least one of a manganate spinel represented by an empirical formula of Li (1+x1) (Mn 1-yl A' y1 ) 2-x1 O z1 and an olivine compound represented by an empirical formula of Ly (1-x2) A" x2 MPO 4 . In another embodiment, an active cathode material comprises a mixture that includes: a lithium nickelate selected from the group consisting of LiCoO 2 -coated LiNi 0.8 Co 0.15 Al 0.05 O 2 , and Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 ; and a manganate spinel represented by an empirical formula of Li (1+x7) Mn 2-y7 O z7 . A lithium-ion battery and a battery pack each independently employ 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. A system comprises a portable electronic device and a battery pack or lithium-ion battery as described above.