Oxygen-doping Or Pore-construction Of A Nano-sized Carbon Black And Its Supercapacitive Performance

Supercapacitors have attracted much attention due to their high power density,ultralong cycle life and subsecond charging.The electrode material is the most important factor affecting the performance of the supercapacitor,and has been highly valued by many researchers.At present,carbon materials,metal oxides and conductive polymers have been as electrode materials used in supercapacitors.Carbon materials have become a research hotspot due to their low cost,excellent electrical conductivity,safety and environmental protection.The rapid development of portable electronic products urgently requires a small but large capacity supercapacitor.The spherical nano-carbon black has a high bulk density and it has an unique advantage as an electrode material applied in a small-sized supercapacitor.However,its specific capacitance is very low.Therefore,this paper aim to obtain excellent electrode materials by doping with surface oxygen,building pores structure and compositing treatment with other materials,which taking low-cost nano-carbon black as the object of study.The main research works and results of this paper are list as following:A spherical carbon black?CB?with an average particle size of 30 nm was used as an object to construct a supercapacitor electrode material which has a dense structure.In this paper,CB was first activated by KOH and then oxidatively doped to obtain oxygen-doped carbon black?DCB?,and the effects of specific surface area and pore structure of the prepared DCB on its electrochemical performance were systematically studied.The experimental results show that the total specific surface area(from 250.15 m² g^-1 to 234.86m² g^-1)and pore volume(from 0.816 cm³ g^-1 to 0.416 cm³ g^-1)of nano-CB were significantly decreased after the oxygen-doping treatment,but the specific capacitance of raw CB has increased from 11 F g^-1 to 233 F g^-1at a scan rate of 5 mV s^-1.What's more,oxygen-doping makes the carbon nanoballs more tightly packed.The volumetric capacitance of DCB reaches up to 253 F cm^-3.In addition,DCB also shows an excellent cycling stability and its capacitance remains 92%even after 5000 cycles.Because of its advantages in mass production and low cost,the oxygen-doped nano-sized carbon black can be considered as a competitive candidate for the mass production of the electrode materials for high volumetric performance supercapacitors.In view of the fact that the specific surface area of oxygen-doped nano-carbon black is too low to provide more adsorption space for electrolyte ions,this paper adopts KOH activation and intercalation puffing to treat carbon black to increase its specific surface area and analysis of the impact on the structure and electrochemical properties of the carbon black primary and secondary puffed expanding treatment.The results show that the specific surface area of nano-carbon black can be significantly improved by the bulking treatment,and the specific surface area of the first-extruded nano-carbon black?CBP-1?and the second-extended nano-black carbon?CBP-2?is 996.34 m² g^-1 and 1126.51 m² g^-1,respectively,both higher than the original CB of 250.15 m² g^-1,and the total pore volume of the material also increased significantly.At a scan rate of 5 mV s^-1,the specific capacitance of CBP-2 is 234 F g^-1,which is much higher than that of CBP-1(162 F g^-1).The reason for this should be attributed to the second extrusion,leading to the higher specific surface area and well-developed pore structures.At the same time,CBP-2 has a specific capacitance retention of 93.5%after 10000 cycles,showing a good cycle stability.In order to obtain an electrode material with superior performance for supercapacitor,the graphene nanoplatelets?GNP?and CBP-2 were composited in different mass ratios to prepare CBP-2/GNP composites.The results show that CBP-2 can effectively prevent the interlayer stacking of GNP by entering the GNP layer,which providing more channels for the rapid transmission of electrolyte ions.The CBP-2/GNP composite has a specific capacitance of 144 F g^-1 at a scan rate of 5 mV s^-1,but its cyclic voltammogram can still maintain a rectangular shape at a high scan rate of 5 V s^-1,which shows excellent power characteristics.At the same time,the CBP-2/GNP composite only lost 1.5%of the specific capacitance after 10000 cycles,indicating the excellent long-cycle stability.