Abstract: A high-voltage lithium-ion battery cathode material includes LiNi0.5-xMn1.5MxO4 (0?x?0.2, M?Mg, Zn, Co. Cu, Fe, Ti, Zr, Ru, and Cr), which is coated with a coating material, which may be a carbon coating material, a metal phosphate coating material, or a combination thereof. The carbon coating material may be acetylene black, graphene oxide, conductive graphite, glucose, sucrose, starch, lactose, maltose, phenolic resins, polyvinyl alcohol, or a combination thereof, and the metal phosphate coating material may be FePO4, LiFePO4, CoPO4, Mn3(PO4)2, LnPO4. The coating material may account for 1 to 10% (wt %). Products of the present invention have high reversible capacities. Synthesis methods are disclosed that are simple and controllable, can produce uniform coating, and are suitable for industrial scale production.