▎ 摘　　要

NOVELTY - Preparing graphene coated nano-graphite electrode material involves preparing large-sized graphene oxide by adding 300-500 mu m crystalline flake graphite into mixed acid of sulfuric acid and nitric acid, stirring at 300-500 rotations per minute speed for 24-48hours and filtering to obtain black powder. The black powder is washed with distilled water for 3-5 times and then dried at 60-80 degrees C for 12-24hours. The dried black powder is placed into a microwave oven for 180-60 seconds to obtain the vermicular graphite, where the power of 500-1000 Watt. USE - Method for preparing graphene coated nano-graphite electrode material that is used as cathode material of lithium ion battery (claimed). ADVANTAGE - The method enables to prepare graphene coated nano-graphite electrode material for cathode material of button-typed lithium ion battery which capacity of 0.1Coulomb /- 362milliamp hour/gram, coulomb efficiency is /-89%, after 500 cycle capacity retention is /-92%. DETAILED DESCRIPTION - Preparing graphene coated nano-graphite electrode material involves preparing large-sized graphene oxide by adding 300-500 mu m crystalline flake graphite into mixed acid of sulfuric acid and nitric acid, stirring at 300-500 rotations per minute speed for 24-48hours and filtering to obtain black powder. The black powder is washed with distilled water for 3-5 times and then dried at 60-80 degrees C for 12-24hours. The dried black powder is placed into a microwave oven for 180-60 seconds to obtain the vermicular graphite, where the power of 500-1000 Watt. The grain of crystalline flake graphite is added to mixed acid of sulfuric acid and nitric acid in the ratio of 300-500 mu :(400-450 ml). The sulfuric acid and nitric acid are in volume ratio of 3:1. The vermicular graphite and potassium permanganate are mixed into 98wt.% sulfuric acid, and then reacted for 1-2hours in a ice bath to obtain mixed solution A. The mixed solution A is treated at 30-40 degrees C in heat preservation for 1-3hours. The de-ionized water is added at 90-95 degrees C for 30-50 minutes and cooled naturally to the room temperature to obtain the mixed solution B. The vermicular graphite and potassium permanganate are in a mass ratio of 1:5. The volume ratio of the sulfuric acid mass and the mass fraction of the vermicular graphite is 1 gram:200ml. The vermicular graphite and de-ionized water are in the volume ratio of 1gram:(130-140 ml). The mixed solution B is added to 35% hydrogen peroxide solution, and stirred uniformly at room temperature for 10-30 minutes to obtain oxidized graphene water solution. The graphene oxide aqueous solution is at stirred at a speed of 6000-10000rotations per minute and centrifuged and the precipitate is collected. The deposition is carried out at 60-80 degrees C for 12-48hours to obtain the large-size graphene oxide. The mixed solution B is added to 35% hydrogen peroxide solution in the volume ratio of 50:(1-2). The large-size graphene oxide is dissolved in water to obtain a large size graphene oxide solution. The concentration of large-size graphene oxide solution is 5-15 gram/l. The nanometre graphite powder and polyimide acid solution are mixed into the distilled water. The stirring speed is 300-500rotations per minute and reacted for 20-40 minutes to obtain the mixed solution of nano-graphite powder and polyimide acid. The nano-graphite powder and distilled water are in volume ratio of (3-10 gram):400ml. The polyimide acid water solution and distilled water are in volume ratio of (0.5-2):400. The mixed solution is treated ultrasonically for 0.5-2hours to obtain deep color mixed solution in ultrasonic power and dried. The obtained dark solution is stirred at 140-170 degrees C. The obtained fluffy powder is placed into a tubular furnace. The temperature of tubular furnace is raied from room temperature at a heating rate of 3-5 degrees C/minute under the protection of inert gas to obtain fluffy powder. The heat preservation is carried out for 50-80 minutes at 180-240 degrees C, then at 900-1100 degrees C for 120-150 minutes. The temperature is reduced at a cooling rate of 5-8 degrees C/minute, and then naturally cooled to room temperature, and the annealing treatment is finished and graphene coated nano-graphite electrode material is obtained.