▎ 摘　　要

NOVELTY - Preparation of graphene-coated silver powder involves adding graphene oxide to solvent, ultrasonically processing at 300-1000 W for 0.5-1.5 hours, obtaining oxide graphene suspension, adding silver powder to oxide graphene suspension, dispersing, obtaining mixed solution, adding mixed solution to hydrothermal reactor, reacting at 170-190 degrees C for 10-20 hours, naturally cooling to room temperature, washing using ultrapure deionized water, further cleaning using anhydrous ethanol, and vacuum-drying at 50-70 degrees C for 3-5 hours. USE - Preparation of graphene-coated silver powder used for crystalline silicon solar battery. ADVANTAGE - The method efficiently and economically provides graphene-coated silver powder. DETAILED DESCRIPTION - Preparation of graphene-coated silver powder involves mixing 30-500 g/L silver nitrate solution and 10-100 g/L dispersant solution in the volume ratio of 0.3-3:1, obtaining silver nitrate solution containing dispersant, dissolving a reducing agent in distilled water, obtaining 50-150 g/L reducing agent solution, mixing reducing agent solution with silver nitrate solution containing dispersant, stirring at 20-30 degrees C for 0.5-2 hours at the speed of 100-200 rpm, separating by filtration, centrifuging, washing obtained solid material using distilled water, further washing using anhydrous ethanol, drying at 70-90 degrees C for 2-6 hours, obtaining silver powder, adding graphite powder into 98 %mass sulfuric acid under ice water-bath condition in the mass ratio of 1 g:10-50 ml, adding potassium permanganate powder, stirring at 100-300 rpm, obtaining mixture liquid (I), heating mixture liquid (I) at 30-40 degrees C, stirring at 100-300 rpm for 20-40 minutes, adding ultrapure deionized water, stirring at the speed of 100-300 rpm, heating at 95-100 degrees C for 10-20 minutes, obtaining mixed solution (II), adding ultrapure deionized water to mixed solution (II), adding 30 %mass hydrogen peroxide, mixing, centrifuging, obtaining solid material, washing resultant material using 5 %mass hydrochloric acid until the cleaning solution is not able to detect sulfate ions, obtaining cleaned solid material, processing cleaned solid material at 20-30 degrees C for 8-12 hours, obtaining graphene oxide, adding obtained graphene oxide to a solvent, ultrasonically processing at 300-1000 W for 0.5-1.5 hours, obtaining oxide graphene suspension, adding silver powder to oxide graphene suspension, dispersing at 100-300 rpm in the ultrasonic power of 100-500 W for 1-5 hours, obtaining mixed solution (III), adding mixed solution (III) to hydrothermal reactor, reacting at 170-190 degrees C for 10-20 hours, naturally cooling to room temperature, washing using ultrapure deionized water, further cleaning using anhydrous ethanol, and vacuum-drying at 50-70 degrees C for 3-5 hours. The volume ratio of reducing agent solution with respect to silver nitrate solution containing dispersant is 1:1-3. The mass ratio of graphite powder with respect to potassium permanganate powder is 1:5-10. The volume ratio of mixed liquid (I) with respect to ultrapure deionized water is 1:2-4. The volume ratio of mixed solution (II) with respect to ultrapure deionized water is 1:2-5. The volume ratio of mixed solution (II) with respect to 30% mass hydrogen peroxide is 1:0.1-0.6. The volume ratio of graphene oxide with respect to solvent is 1 g: 1-10 mL. The mass ratio of silver powder with respect to graphene oxide suspension is 1 g:1-10 mL. An INDEPENDENT CLAIM is included for preparation of graphene-coated silver-modified lead-free paste, which involves using graphene-coated silver powder.