▎ 摘　　要

NOVELTY - A graphene/carbon nanotube/graphene composite material comprises a carbon nanotubes having an inner diameter of 50 nm to 100 mu m and outer diameter of 55 nm to 200 mu m, and graphene deposited on the inner and outer surfaces of the carbon nanotubes. The bonding between graphene and carbon nanotubes is a chemical bond. The number of layers of graphene is 1-20. USE - Graphene/carbon nanotube/graphene composite material is used in preparation of composite phase change energy storage material and for forming composite electrode (all claimed) of supercapacitor and lithium-ion battery. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) preparation of graphene/carbon nanotube/graphene composite material, which involves carrying out high-temperature carbonation of a washed natural biomass comprising lignin, cellulose and/or hemicellulose in presence of presence or absence of catalyst, obtaining hollow tubular carbon nanotubes, and growing graphene on the carbon nanotubes; (2) composite phase change energy storage material, which is obtained by filling a phase change material in the graphene/carbon nanotube/graphene composite material. the phase change material includes stearic acid, palmitic acid, N-tetradecane, N-pentadecane, wood alloy and/or oleic acid; (3) preparation of composite phase change energy storage material; and (4) composite electrode, which is obtained by loading the graphene/carbon nanotube/graphene composite material in electrode material of supercapacitor and/or lithium-ion battery to form a composite electrode. The electrode material of the supercapacitor comprises nickel oxide, manganese oxide, polymeric polyaniline, polypyrrole and/or polythiophene. The positive electrode material of the lithium-ion battery comprises lithium-iron phosphate, lithium-manganese oxide, lithium-cobalt oxide and binary/ternary cathode materials. The negative electrode material of the lithium-ion battery comprises lithium titanate, silicon, tin and tin oxide.