(103g) A Cost-Effective Supercapacitor Material of Ultrahigh Specific Capacitances: Spinel Nickel Cobaltite Aerogels From An Epoxide-Driven Sol-Gel Process

Low cost mesoporous materials of high specific surface area, porosity, electronic conductivity, and electrochemical activity, and multiple oxidation states/structures are desired for next generation supercapacitors. These requirements for material characteristics can be met by the nickel cobaltite (NiCo2O4) aerogels prepared from an epoxide-driven sol-gel process. In this work, nickel cobaltite aerogels of ultrahigh specific capacitance (1,400 F/g at a relatively high mass loading of 0.4 mg/cm2, a sweep rate of 25 mV/s, a potential window of 0.04 - 0.52 V in a 1M NaOH solution), excellent reversibility, and outstanding cycle stability were synthesized with a chloride based epoxide addition procedure for the first time. The post-gel-drying calcination temperature was found to play a critical role in producing the preferred products. Nickel cobaltite aerogels of outstanding supercapacitive properties were obtained with a starting Ni/Co ratio of 0.5 and post-gel-drying calcination temperature of 200 oC, achieving an optimal combination of composition, crystallinity, specific surface area, pore volume, and pore size. The development of the present work makes possible the low cost production of next generation, ultrahigh performance supercapacitors of the asymmetric type. The content of this paper is to appear in Adv. Mater.