Asymmetric supercapacitors based on Co, Ni and polypyrrole pseudocapacitive electrodes

Abstract

Firstly, cobalt hydroxide nanowires network were grown on nitrogen doped microwave exfoliated graphite oxide OsJMEG). The specific capacitance can reach 610 F/g. Asymmetric pseudocapacitor devices were fabricated with Co(OH)2^IMEG as the positive electrode and polypyrrole(PPy)/rG-0 as the negative electrode. The Co(OH)2ANMEG//PPy/rG-O asymmetric supercapacitor have a high energy density of 24.9 WhTcg, significantly higher than a number of other devices fabricated and tested under the same measurement condition. PPy/rG-0 is proven to be a superior negative electrode to be used with transition metal based electrodes with narrow voltage window for supercapacitor devices. Secondly, Ni-Co-S and polypyrrole on vertically-aligned carbon nanotubes array (VA- CNTs)/3D carbon fiber paper (CFP) are developed as freestanding electrodes for supercapacitors. The binder-free asymmetric supercapacitor devices with Ni-Co-S/VA- CNTs/CFP as the positive electrode and polypyrrole/VA-CNTs/CFP as the negative electrode respectively demonstrates high energy density of 82 WMcg at 200 W/kg.