Graphene polymer composite material

A graphene polymer composite material, comprising:

• a plurality of nano-scaled graphene sheets being 0.01-20 wt % (weight percent) of the graphene polymer composite material;
• a matrix resin being 40-99 wt % of the graphene polymer composite material;
• and
• a filler being 1-40 wt % of the graphene polymer composite material,
• wherein the nano-scaled graphene sheets are dispersed in the matrix resin, the filler is in contact with the plurality of nano-scaled graphene sheets so as to construct an electrically conductive network structure,
• wherein a thickness of the plurality of nano-scaled graphene sheets is 10-100 nm, a lateral size of the plurality of nano-scaled graphene sheets is 1-100 μm, and a ratio of a particle size of the filler to the thickness of the graphene sheet is 2-1000, and
• wherein the plurality of nano-scaled graphene sheets has at least one surface-modified layer formed by covering at least one surface modifying agent, the surface modifying agent is selected from a coupler having a chemical formula specified by Mx(R)y(R′)z, M is a metal element, R is a hydrophilic functional group, R′ is a hydrophobic functional group, 0≦x≦6, 1≦y≦10, 1≦z≦20, the plurality of nano-scaled graphene sheets further has an oxygen content of 3-20 wt %, and the hydrophilic and hydrophobic functional groups form chemical bonds with the matrix resin and the filler.