Construction of hierarchical Co-Ni-S nanosheets as free-standing electrode for superior-performance asymmetric supercapacitors

Abstract

Co-Ni-S nanoarchitectures with considerable conductivity and superior electrochemical performance have been successfully designed and grown on Ni foam substrates. The collective effects of structure and composition endow Co-Ni-S electrodes better electrochemical performance with ultra-high areal capacitances of 6.3 F cm−2 at 1 mA cm−2 (4.2 F cm−2 retained at 8 mA cm−2) and remarkable rate capability of 65% at 10 mA cm−2. Correspondingly, asymmetric supercapacitors are assembled with Co-Ni-S sample and active carbon as the positive and negative electrodes, which display an excellent energy density of ∼50 Wh kg−1 at a power density of ∼0.783 kW kg−1. Furthermore, the capacitance maintains 71% of the initial value after cycling 6000 times at 1 A g−1. These results have great significance for the optimization of asymmetric supercapacitors as the energy-storage devices for the next generation.