Lithium supplement additive, preparation method thereof, positive electrode material and secondary battery

The invention provides a lithium supplement additive and a preparation method thereof, a positive electrode material and a secondary battery. The lithium supplement additive comprises a lithium supplement material and a metal compound, the metal compound is combined to the lithium supplement material, the lithium removal decomposition potential of the lithium supplement material is larger than or equal to 4.2 V, and at least part of metal atoms in the metal compound are doped into crystal lattices of the lithium supplement material. The metal compound is used for catalyzing decomposition of the lithium supplementing material so as to reduce the lithium removal decomposition potential of the lithium supplementing material. The metal compound provided by the invention has catalytic performance, so that the lithium supplementing material can fully remove lithium at a relatively low potential. Meanwhile, metal atoms are doped into lattices of the lithium supplementing material, so that the binding force of the li