▎ 摘　　要

NOVELTY - Preparation of graphene-based composite material involves mixing (i) magnesium salt solution and carbonate solution, filtering and washing by suction filtration, dispersing solid material in water to obtain dispersion slurry, mixing the slurry with slurry containing silicon powder to obtain precursor, heating (ii) the precursor in high temperature reactor, introducing gas (a) containing protective gas and hydrogen into high temperature reactor, placing (iii) composite material containing magnesium oxide and silicon in high-temperature reactor, heating, introducing protective gas, reaching the predetermined temperature (b), introducing the gas (b) containing protective gas and carbon source or containing protective gas and nitrogen containing carbon source into the reactor, and form graphene or nitrogen-doped graphene on the composite material containing magnesium oxide and silicon, and removing (iv) magnesium oxide in the composite material containing magnesium oxide and silicon. USE - Preparation of graphene-based composite material for forming cathode material used for lithium battery for automobiles (all claimed). DETAILED DESCRIPTION - Preparation of graphene-based composite material involves mixing (i) magnesium salt solution and carbonate solution, filtering and washing by suction filtration, dispersing solid material in water to obtain dispersion slurry, mixing slurry with slurry containing silicon powder, and spray drying to obtain precursor, heating (ii) the precursor in high temperature reactor, introducing gas (a) containing protective gas and hydrogen into high temperature reactor, placing (iii) composite material containing magnesium oxide and silicon in high-temperature reactor and heating, introducing protective gas, reaching the predetermined temperature (b), introducing the gas (b) containing protective gas and carbon source or containing protective gas and nitrogen containing carbon source into the high temperature reactor, and form graphene or nitrogen-doped graphene on the composite material containing magnesium oxide and silicon, and removing (iv) magnesium oxide in the composite material containing magnesium oxide and silicon and washing to neutrality. An INDEPENDENT CLAIM is included for preparation of cathode material, which involves using the graphene-based composite material, a binder, and a conductive agent in mass ratio of (5-95):(1-10):(0-10). The binder comprises at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose and polyacrylic acid. The conductive agent is at least one of carbon nanotubes, acetylene black and conductive carbon black.