Method for preparing high-rate and long-cycle lithium ion battery silicon-based composite material

The invention discloses a method for preparing a silicon-based composite material of a lithium ion battery. The method comprises the following steps: (1) carrying out particle crushing and size grading on silicon powder to obtain non-crystallized silicon powder; (2) mixing sulfur, Na2S. 9H2O and an alkali solution, heating, stirring and dissolving, adding the non-crystallized silicon powder and graphene oxide into the mixed solution, continuously stirring, fully mixing, dropwise adding an acidic solution, adjusting the pH value to be acidic, and when precipitates in the solution are not increased any more, carrying out suction filtration and washing with deionized water until the pH value is close to neutral; carrying out hydrothermal reduction reaction on the precipitate and a graphene oxide reducing agent to obtain a product; and (3) carrying out carbon coating on the product to obtain the silicon-based composite material with good rate capability and long cycle life. The surface of the amorphous silicon is