Low-cost fabrication of amorphous cobalt-iron-boron nanosheets for high-performance asymmetric supercapacitors

The ultrathin amorphous Co-Fe-B nanosheets on the three dimensional nickel foam substrate is fabricated by a facile one-step chemical reduction method. Due to the amorphous structure and ultrathin nanosheet morphology, the Co-Fe-B material shows an excellent specific capacitance ( approximate to 981 Fg(-1) at 1 Ag-1) and high rate performance. In addition, the Co-Fe-B//active carbon (Co-Fe-B//AC) asymmetric supercapacitors were prepared. The ASC shows a maximum energy density of 21 W h kg(-1) (calculated by active materials weight). It also displays excellent long-term stability and the capacitance increase 26% after 5000 cycles. These outstanding supercapacitor performances demonstrate Co-Fe-B material as a low cost candidate material applying to energy storage and conversion. (C) 2018 Elsevier Ltd. All rights reserved.