Surface-modified battery composite material as well as preparation method and application thereof

The invention discloses a surface-modified battery composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: uniformly coating the surface of a battery active material with a carbon fluoride material to obtain an initial composite material; the initial composite material is pretreated, the fluorinated carbon material on the surface of the battery active material generates a surface film rich in nano L < i > F and inorganic carbon through an in-situ reaction, and the surface-modified battery composite material is obtained; a surface film of the battery composite material comprises nano L < i > F and inorganic carbon; the particle size of the nano L < i > F is 3-8 nm; the mass of the nano L < i > F accounts for more than 0 and less than or equal to 4.5 wt% of the total mass of the battery composite material; when the battery composite material disclosed by the invention is applied to the secondary battery, the secondary battery can have hig