Ni-Bi-S nanosheets/Ni foam as a binder-free high-performance electrode for asymmetric supercapacitors

Abstract

Supercapacitors are attracting tremendous interests in electrochemical energy storage and binary metal sulfides are attracting increasing attention due to higher electrochemical activities over their monometal counterparts. In this report, we show a novel Ni-Bi-S nanosheets/Ni foam electrode with superior performance for supercapacitors. In the synthetic process, Ni foam is utilized as current collector as well as Ni source for the Ni-Bi-S. Bi source plays a crucial role to achieve desired morphology for the Ni-Bi-S and uniform nanosheets network can be obtained by controlling the amount of the Bi (NO3)2. The Ni-Bi-S nanosheets/Ni electrode demonstrates a high specific capacitance of 4.81 F/cm2 at 5 mA/cm2 and an outstanding cycling performance. After 3000 cycles, 97.6% of the initial capacitance can be retained at 20 mA/cm2 and the retention is still as high as 83.4% even after 6500 cycles. An asymmetric supercapacitor constructed with Ni-Bi-S cathode and commercial conductive cloth (CC) anode demonstrates with a high energy density of 2.96 mWh/cm3 and a good retention rate after 2000 cycles.