Carbon cloth supported flower-like porous nickel-based electrodes boosting ion/charge transfer characteristics of flexible supercapacitors

Abstract

Despite low cost and high theoretical specific capacitances, nickel-based compounds still suffer from poor conductivity, limited redox active sites and sluggish ion and charge transfer for their applications in flexible supercapacitors (FSCs). The rational structural control of nickel-based compound electrodes is vital but very challenging. Herein, a series of flower-like nickel-based compound electrodes are grown on carbon cloth (CC) by a general synthetic method, including Ni(OH)2/CC, NiS2/CC, NiO/CC and Ni2P/CC hybrid electrodes. The formation mechanism of such flower-like structure is investigated in-depth. Benefiting from the fibrous structure of flexible carbon cloth and flower-like porous structure of NiS2, the NiS2/CC hybrid electrodes are more accessible for the electrolyte ions, which facilitates their electrochemical kinetics and capacitive performances. The maximum specific capacitance of the NiS2/CC electrode is 1166.3 F/g at 0.4 A/g. Moreover, flexible asymmetric supercapacitors (FASCs) are assembled using NiS2/CC and activated carbon/CC (AC/CC) as positive and negative electrodes, respectively. Such FASCs exhibit an energy density of 34.1 Wh/kg at a power density of 561.3 W/kg, a long lifetime stability (96% retention after 8,000 cycles), and excellent mechanical stability. These superior electrochemical characteristics make the flower-like porous NiS2/CC hybrid a good candidate for next-generation flexible and high-performance electrode in FSCs.