New symmetric and asymmetric supercapacitors based on high surface area porous nickel and activated carbon

摘要

We have studied some supercapacitor cell assemblies based on high surface area nickel and nickel oxide materials. Both symmetric and asymmetric configurations consisting of nickel and nickel oxide with activated carbon as a negative electrode have been investigated. A single electrode specific capacitance value of 473 F g~(-1) of nickel is obtained for the porous nickel. We have used cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge-discharge profile analysis to characterize the supercapacitor cell assemblies. Based on the analysis of impedance data in terms of complex capacitance and complex power, the relaxation time constant (TAU_0) was calculated for different supercapacitor cell assemblies. The quick response time (of the order of milliseconds) with fast energy delivery at relatively high power suggests that these materials can find applications in short time pulse devices. A coulombic efficiency of 0.93-0.99 is obtained for the supercapacitor cell assemblies studied in this work. The measured equivalent series resistance (ESR) value is relatively high due to the contribution from the resistance offered by the pores and the contact resistance arising from the cell fabrication method. Although the specific capacitance values are relatively less, the cell exhibits a fast response time, which is a desirable property in certain specialized applications.