Electrochemical and thermal behavior of aluminum- and magnesium-doped spherical lithium nickel cobalt mixed oxides Li1−x(Ni1−y−zCoyMz)O2 (M = Al, Mg)

An industrial synthesis process for spherical lithium nickel cobalt mixed oxides, Li(Ni1−yCoy)O2, has been successfully applied to aluminum- and magnesium-doped lithium nickel cobalt mixed oxides Li(Ni1−y−zCoyMz)O2 (M=Al, Mg). The additional elements stabilize the layered structure and enhance the cycling stability. The decomposition temperature of charged electrodes depends on the delithiation state and the crystallite size but not directly on the content of dopants. Therefore, enhancement of the thermal stability by aluminum and magnesium seems mainly to be an indirect effect due to an intrinsic limitation of the delithiation.