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

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 °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 °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.