Expanded graphite and nano-silicon composite material, preparation method thereof, electrode plate and battery

The invention provides a preparation method of a high-density expanded graphite and nano-silicon composite material. The preparation method comprises the following steps: step S1, oxidizing graphite to manufacture graphite oxide; step S2, carrying out heat treatment on the graphite oxide to manufacture expanded graphite; step S3, mixing the expanded graphite with nano-silicon and a carbon source and carrying out ball-milling to obtain a high-density expanded graphite and nano-silicon composite material precursor comprising a plurality of graphite layers, the carbon source and the nano-silicon filled among the graphite layers; step S4, carrying out heat treatment on the high-density expanded graphite and nano-silicon composite material precursor so that the carbon source is converted into amorphous carbon; and step S5, depositing carbon or doped carbon on the surface of the high-density expanded graphite and nano-silicon composite material precursor after the heat treatment. Moreover, the invention also provides the high-density expanded graphite and nano-silicon composite material, an electrode plate applying the high-density expanded graphite and nano-silicon composite material, and a lithium ion battery applying the electrode plate.