(S1) dissolving a graphite anode powder in an acid solution, and conducting solid-liquid separation- to obtain a precipitate; and washing and drying the precipitate, adding a reducing agent, and subjecting a resulting mixture to heat treatment to obtain a purified graphite material; wherein the heat treatment is heating the resulting mixture of a dried precipitate and the reducing agent in a chlorine atmosphere; and

(S2) mixing a modified silicon powder with the graphite material, adding to a polyimide-containing N,N-dimethylformamide solution, and stirring; and subjecting a resulting mixture to distillation and then to carbonization to obtain the silicon/carbon composite anode material; the modified silicon powder is a silicon powder modified by a silane coupling agent solution; and the silane coupling agent solution is obtained by hydrolyzing a silane coupling agent with an aqueous acetic acid solution; the silane coupling agent is one selected from the group consisting of γ-methacryloxypropyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane.