Supercapacitive behavior of an asymmetric supercapacitor based on a Ni(OH)2/XC-72 composite

Abstract

A Ni(OH)₂/Vulcan XC-72 (XC-72) composite has been synthesized by a microwave assisted method; it demonstrated a high specific capacitance of 1560 F g⁻¹ at 1 A g⁻¹ with carbon nanotubes as conductive agents. Ni(OH)₂/XC-72, activated carbon (AC) and non-woven fabric were, respectively, used as a positive electrode, a negative electrode and a separator to assemble an asymmetric supercapacitor. This AC//Ni(OH)₂/XC-72 supercapacitor achieves a remarkable capacitance of 92.2 F g⁻¹ at a current density of 0.5 A g⁻¹, a maximum energy density of 36 W h kg⁻¹ and a power density of 490 W kg⁻¹ based on an active material in a 6 M KOH aqueous electrolyte with a negative/positive electrode mass ratio of 1.75 within a voltage window of 1.6 V. Furthermore, the capacitance of the unit supercapacitor remains 85% after 1000 charging–discharging cycles. These results indicate that the AC//Ni(OH)₂/XC-72 supercapacitor is promising to be applied in a practical device for energy storage.