Composite lithium supplementing material and preparation method and application thereof

The invention relates to the technical field of lithium batteries, and provides a composite lithium supplementing material and a preparation method and application thereof. The composite lithium supplementing material is of a core-shell structure and comprises an inner core and an outer shell, the inner core comprises a binary lithium-rich material A, the outer shell comprises a binary lithium-rich material B, the chemical formula of the binary lithium-rich material A and the chemical formula of the binary lithium-rich material B are LixMy, x is larger than or equal to 1 and smaller than or equal to 5, y is smaller than or equal to 1, the chemical formula of the binary lithium-rich material A comprises one element of N, P, S, F, I, Br, B, O and Se, and the chemical formula of the binary lithium-rich material B comprises the other element of N, P, S, F, I, Br, B, O and Se. The composite lithium supplement material provided by the invention can provide abundant lithium, so that the lithium supplement material c