Bio-mediated synthesis of α-Ni(OH)2 nanobristles on hollow porous carbon nanofibers for rechargeable alkaline batteries

Abstract

Nickel hydroxide nanobristles were fabricated on the surface of hollow carbon nanofibers (HPCNFs) through a low cost and effective bio-mediated technology, where the eggshells with eggshell membrane were selected as multifunctional reactors to separate the precursor solution to control OH− ion diffusion in order to form α-Ni(OH)2 instead of β-Ni(OH)2. The as prepared Ni(OH)2/HPCNFs displays high capacity (283 mAh/g) and a remarkable cycle life (82% specific capacity retained after 5000 cycle numbers) in 1M KOH aqueous solution. Compared with literature reports, in which Ni(OH)2 are often considered for pseudocapacitors, we suggest our electrodes are good for rechargeable alkaline secondary batteries or as battery electrodes in hybrid supercapacitors, based on battery behavior observed in our electrochemical measurements. As battery electrodes in hybrid supercapacitors, an asymmetric supercapacitor was fabricated, in which Ni(OH)2/HPCNFs and activated carbon as positive and negative electrode, respectively (Ni(OH)2/HPCNFs//AC ASC), which displays intriguing electrochemical performances with a high energy density (31.3 Wh /kg at 300.5 W/ kg). The results demonstrate that the bio-mediated method for achieving Ni(OH)2/HPCNFs nanomaterials is becoming a promising technology in alkaline batteries.