The invention relates to a modified
lithium-based composite negative material for a
solid state battery and preparation and application of the material. The modified
lithium-based composite negative material comprises 50-95 parts of
lithium and 5-50 parts of a modified additive by weight; and the modified additive comprises one or multiple
nitride or
fluoride. The preparation method comprises thatthe lithium and modified additive are mixed, heated to 180-400 DEG C, stirred uniformly, and cooled to the
room temperature; and the modified composite negative material is used to the
solid state battery, and combined with a
solid electrolyte. Compared with the prior art, the
lithium metal is mixed with the modified additive by mixing in a heating fusing way, the
surface energy of the
lithium metal can be reduced effectively, elements including
nitrogen and
fluorine are introduced in a controllable way, the
interfacial resistance between the solid
electrolyte and lithium
cathode is reduced effectively, the limit current that can be born by the solid
electrolyte is increased, the recyclable
charge and discharge capacity is improved, and the solid electrolyte and
cathode interface is stable for a longer time in the long circulation process.