Carbon microspheres with micro- and mesopores synthesized via spray pyrolysis for high-energy-density, electrical-double-layer capacitors

Abstract

The graphitic properties, optimized pore structure, and surface chemistry of carbon materials are important factors for developing high-performance supercapacitors. In this study, we synthesized partially graphitic carbon microspheres with large surface area and multimodal pore-size distribution (high amount of micropores and small amount of mesopores) using a facile spray pyrolysis process. Vanadium oxide-carbon microspheres were synthesized via spray pyrolysis at 1000 degrees C. Subsequently, selective etching of vanadium oxide using NH4OH solution resulted in porous carbon (PC) microspheres with large surface area and multimodal pore structure. The post-treatment process of PC microspheres at 900 degrees C in Ar atmosphere enabled not only the synthesis of partially graphitic carbon microsphere via graphitization, but also the elimination of organic functional groups at the carbon surface. The supercapacitor fabricated with post-treated PC microspheres (PC-900) with a voltage window of 2.5 V exhibited high specific capacitance (110 F g(-1) at 30 A g(-1)) and excellent rate capability in an organic electrolyte. The PC-900 supercapacitor could also produce high energy density (23 Wh kg(-1)) even at high power density (42 kW kg(-1)). In addition, the PC-900 supercapacitor exhibited excellent cyclability with capacitance reduction of approximately 5% after 10,000 cycles.