Method for preparing graphite-based Si@C negative electrode material by taking silica fume as Si source

The invention discloses a method for preparing a graphite-based Si@C negative electrode material by taking micro-silicon powder as a Si source. The method comprises the following steps: pretreating the micro-silicon powder, then carrying out ball-milling mixing and reduction reaction on the micro-silicon powder and magnesium powder, and carrying out acid pickling and centrifugal drying to obtain porous crystal Si particles; and uniformly mixing the prepared porous crystal Si with dopamine in a prepared Tris buffer solution with the pH value of 8.5 to deposit polydopamine on the surfaces of Si particles, and coating the Si to prepare the composite material with the Si-C core-shell structure. The composite material has excellent electrochemical performance, relatively high specific capacity, long cycle life, high capacity retention ratio and stable cycle life; the pore structure of the carbon layer and the Si particles wrapped by the carbon layer also shortens the diffusion distance and time for deintercalation