▎ 摘　　要

NOVELTY - In-situ synthesis of zinc vanadate/graphene composite material involves mixing graphene-multi-walled carbon nanotubes with distilled water, adding imidazolium salt-type ionic liquid (I), stirring, interweaving a carbon material using crosslinked graphene ultra-thin nanosheets, adding ammonium metavanadate solid powder, stirring, adding zinc nitrate solution with a concentration of 0.20 mol/L, stirring at 50 rpm for 20 minutes at room temperature, transferring to an atmospheric pressure microwave reactor with a reflux device, reacting by heating for 4-10 hours, slowly cooling the reaction solution to room temperature to obtain a black agglomerated suspension, washing the suspension with distilled water and ethanol, and drying by placing in a constant temperature drying oven at 80 degrees C for 24 hours to obtain absolutely dry black solid flocculant powder. USE - In-situ synthesis of zinc vanadate/graphene composite material used for forming electrode e.g. positive electrode for zinc-ion secondary battery. ADVANTAGE - The method enables energy-saving and efficient in-situ synthesis of zinc vanadate/graphene composite material with improved productivity. DETAILED DESCRIPTION - In-situ synthesis of zinc vanadate/graphene composite material involves weighing (i) 0.1000-2 g graphene-multi-walled carbon nanotubes having excellent conductivity and a specific surface area of 1200-1800 m2/g as a conductive carbon material, uniformly mixing with 50 mL distilled water, transferring to a 200 mL quartz round-bottomed flask container, adding 0.2000 g imidazolium salt-type ionic liquid of formula: ((RMIM)X) (I), stirring at room temperature of 25 degrees C for 1 hour to obtain an uniform suspension (a), and interweaving a carbon material using crosslinked graphene ultra-thin nanosheets, in which interlayer spacing between the nanosheets is 0.37 nm, and single-walled carbon nanotubes with a length of 10-20 mu m and a diameter of 3-5 nm are embedded in-situ on the surface of the graphene, adding (ii) the suspension (a) to an atmospheric pressure microwave reactor with a reflux device, controlling a microwave radiation power of the reactor to 600-1200 W and a heating temperature of the reactor to 80-100 degrees C, and reacting for 1 hour to obtain a suspension (b), fully adsorbing the liquid (I) on each exposed surface of graphene-multi-walled carbon nanotubes during the microwave reaction, and laying a synthetic foundation for the in-situ growth of the patented inorganic nanomaterials on the carbon surface, adding (iii) the suspension (b) to 0.5850 g ammonium metavanadate (NH4VO3) solid powder, and stirring at room temperature for 1 hour until a completely dissolved solution is obtained to obtain a suspension (c), adding (iv) the suspension (c) to a normal pressure microwave reactor with a reflux device, controlling a microwave radiation power of the reactor to 600-1200 W and an internal temperature of the reactor to 80-100 degrees C, and reacting by heating for 5 minutes to obtain a suspension (d), fully adsorbing the ammonium metavanadate on each exposed surface of graphene-multi-walled carbon nanotubes during the microwave reaction, and growing zinc vanadate with in-situ composite specific crystal planes which is attached to the exposed surface of graphene, and adding (v) the suspension (d) to 50 mL zinc nitrate solution with a concentration of 0.20 mol/L, stirring at 50 rpm for 20 minutes at room temperature, transferring to an atmospheric pressure microwave reactor with a reflux device, controlling a microwave radiation power of the reactor to 600-1200 W and an internal temperature of the reactor to 80-100 degrees C, and reacting by heating for 4-10 hours, slowly cooling the reaction solution to room temperature to obtain a black agglomerated suspension (e), washing the suspension (e) 5 times with distilled water and washing 2 times with ethanol, and drying by placing in a constant temperature drying oven at 80 degrees C for 24 hours to obtain absolutely dry black solid flocculant powder as zinc vanadate nanocrystal/graphene-multi-walled carbon nanotube composite material. The inorganic material phase in the composite material includes zinc vanadate monoclinic phase, C2 spatial point group, and a unit cell parameter ( beta ) of 111.55 degrees , as measured by X-ray diffraction test. The diameter of zinc vanadate nanocrystals is 40-80 nm as measured by scanning electron microscope morphology test, which are embedded in-situ on the surface of graphene-multi-walled carbon nanotubes. In high-resolution transmission electron microscopic test, the exposed crystal plane of zinc vanadate nanocrystals is (010) direction. To evaluate electrochemical performance of zinc vanadate nanocrystal/graphene-multi-walled carbon nanotube composite material in zinc-ion secondary battery, a positive electrode shell, a positive electrode active material, a separator which is polyethylene separator, a negative electrode active material which is high-purity zinc foil, and a negative electrode shell are assembled into a button-type battery. The positive electrode active material is connected to the positive electrode shell. The negative electrode active material is connected to the negative electrode shell. The polyethylene separator between the positive electrode and the negative electrode infiltrates an aqueous zinc sulfate electrolyte with a concentration of 0.1-0.5 mol/L. The positive electrode is prepared by mixing zinc vanadate nanocrystal/graphene-multi-walled carbon nanotube composite material, polyvinylidene fluoride powder, Super P (RTM: conductive carbon black) in a mass ratio of 8:1:1, adding a solvent, preferably N-methylpyrrolidone, homogenizing for 2 hours to obtain a black paste, coating the black paste on a surface of an aluminum foil with a thickness of 25 mu m, placing in a vacuum-drying oven, and drying at a constant temperature of 120 degrees C for 10-24 hours. When the assembled zinc-ion battery is tested on a constant current charging/discharging device at a current density of 0.1 C for specific capacity and capacity retention rate of the composite material, the composite material exhibits desired cycle stability. R = 1-6C alkyl;and X = chloride ion, bromide ion, nitrate ion, sulfate ion, tetrafluoroborate ion or acetate ion.