Hierarchically porous Ni-Co oxide for high reversibility asymmetric full-cell supercapacitors

Abstract

Hierarchically porous Ni-Co oxide powder is successfully synthesized by a facile chemical bath deposition method. The structure and composition of Ni-Co oxide are confirmed by transmission electron microscopy and energy dispersive X-ray analysis. Scanning electron microscopy characterization indicates that the Ni-Co oxide has architecture of numerous microflowers with porous flakes. The pseudocapacitive behavior of the Ni-Co oxide powder is investigated by cyclic voltammgrams (CVs) and galvanostatic charge-discharge tests in alkali solution. The Ni-Co oxide shows a good reversibility with a high specific capacitance (834.93 Fg -1 at 1 mVs -1 scan rate). This active material was also used to manufacture a Ni-Co oxideAC (Active Carbon) asymmetric supercapacitor. The Ni-Co oxideAC asymmetric supercapacitor shows not only a high specific capacitance (60 Fg -1 with 1 mVs -1 scan rate), but also a high reversibility where its specific capacitance remains at 37 Fg -1 at a high current density of 20 mAcm -2. © 2012 The Electrochemical Society.