The invention discloses a 
nickel-
cobalt lithium manganate positive 
electrode material applied to high-
voltage lithium ion batteries. The 
chemical formula of 
nickel-
cobalt lithium manganate is Li(NixCoyMn1-x-y)1-a-bLaaAlbO2, wherein a is greater than or equal to 0 and is less than or equal to 0.05, b is greater than or equal to 0 and is less than or equal to 0.1, x is greater than or equal to 0.3 and is less than or equal to 0.8, and y is greater than or equal to 0.05 and is less than or equal to 0.4. A preparation method of the 
nickel-
cobalt lithium 
manganate positive 
electrode material comprises the following steps: carrying out ball milling and mixing a nickel-cobalt-
manganese precursor, a 
lanthanum source, an aluminum source and lithium salt in a horizontal 
ball mill, then pre-sinteringthe obtained mixture in a 
muffle furnace, then carrying out secondary ball milling and mixing the obtained mixture in the horizontal 
ball mill, and finally 
sintering the obtained mixture in a high-temperature tubular furnace to obtain a final product which is nickel-cobalt lithium manganate used as a positive 
electrode material. According to the nickel-cobalt lithium manganate positive electrodematerial, La and Al are co-doped in the nickel-cobalt lithium manganate positive 
electrode material; the interplanar 
crystal spacing can be increased, so that the migration of lithium ions can be accelerated; the stability of the lithium-
free state of the 
crystal structure under 
high voltage can be improved; meanwhile, the 
crystal lattice volume and the stress expansion can be effectively reduced;the nickel-cobalt lithium manganate positive 
electrode material has the characteristics of high capacity and excellent cycle performance under 
high voltage; the disordered-ordered 
phase change underhigh 
voltage of the nickel-cobalt lithium manganate positive 
electrode material can be effectively inhibited; the problem of rapid capacity attenuation of the material in cycle under 
high voltage is solved, so that the service life of the lithium 
ion batteries can be prolonged.