NOVELTY - Preparation of battery involves mixing sulfur and corncob activated carbon, mixing resultant powder, electroconductive carbon and polyvinylidene fluoride, adding N-methylpyrrolidone, coating resultant slurry on aluminum foil current collector, and arranging resultant carbon/sulfur composite material as anode, metal lithium sheet as cathode, Celgard 2300 (RTM: polypropylene micro-porous film) as membrane, and electrolyte including 1 mol/L bis(trifluoromethane)sulfonimide lithium, and solvent including ethylene glycol dimethyl ether and 1,3-dioxolane in a glove box.    USE - Preparation of battery e.g. 2016 button battery and lithium-sulfur battery.    ADVANTAGE - The method enables simple preparation of battery having excellent electrochemical performance, initial discharge specific capacity of to 761.2 mAh/g under current of 0.2 mA/cm2, discharge specific capacity after 20 cycles of 683.2 mAh/g, and capacity retention rate of 89.75%, using economical and easily available corncob activated carbon.    DETAILED DESCRIPTION - Preparation of battery involves preparing corncob activated carbon, mixing sulfur and corncob activated carbon in a mass ratio of 3:1, grinding, mixing, placing resultant mixture in sealed reactor, heating at 150 degrees C for 5 hours and then at 300 degrees C for 3 hours, naturally cooling to room temperature, obtaining carbon/sulfur composite powder, mixing resultant powder, electroconductive carbon and polyvinylidene fluoride for 3 hours, grinding, adding N-methylpyrrolidinone, stirring for 30 minutes, coating resultant slurry on aluminum foil current collector having thickness of 20 mu m, drying at 40 degrees C for 2 hours and then at 80 degrees C for 12 hours, punching into 14 mm wafer and tablet, and arranging resultant carbon/sulfur composite material as anode, metal lithium sheet as cathode, Celgard 2300 (RTM: polypropylene micro-porous film) as membrane, and electrolyte including 1 mol/L bis(trifluoromethane)sulfonimide lithium, and solvent including ethylene glycol dimethyl ether and 1,3-dioxolane in a glove box filled with dry argon. The corncob activated carbon is prepared by impregnating 18 mesh corn core with 70% concentrated phosphoric acid in quartz tank having ceramic tube at 100 degrees C for 18 hours, heating at 10 degrees C/minute for 2 hours, activating in nitrogen atmosphere, cooling to room temperature, soaking resultant product in 10% hydrochloric acid at 90 degrees C for 30 minutes, suction-filtering by double-layer filter paper, washing with distilled water, and drying for 24 hours.