Controlling the electrochemical performance of β-Ni(OH)2/carbon nanotube hybrid electrodes for supercapacitor applications by La doping: A systematic investigation

Abstract

Controlling the electrochemical performance of electrodes for application in supercapacitor has received large research interest in the recent years. Here we report the facile synthesis of a Ni(OH)2 and carbon nanotubes based nanohybrid electrode and control its electrochemical performance for application in supercapacitor by La doping. A systematic investigation of the influence of a number of electrochemical parameters of measurement on the electrode properties is also presented. Structural and morphological analyses show formation of hexagonal nanoparticles (∼35 nm) well attached on the walls of carbon nanotubes (CNT) while elemental analysis confirms the success of La doping. The nanohybrid sample doped with 1 mol% La (with respect to Ni) appears to be the best performing electrode exhibiting specific capacitance of 2731 F/g at 1 A/g, energy density of 25 Wh/kg at power density of ∼1 kW/kg and capacity retention of 84% even after 5000 cycles which are higher than previously reported values for Ni(OH)2 based electrodes and also the first of its kind in which β-Ni(OH)2 has been combined with CNT and doped with La. Increase in the specific surface area as well as electrical conductivity of Ni(OH)2 by incorporation of CNT and La dopants are the main reasons for the improved performance of the 1 mol% La doped composite whereas formation of insulating La(OH)3 is responsible for the inferior performance of electrodes containing more than 1 mol% La. The charge storage mechanism has been found to be governed by both capacitive and diffusion processes at high scan rates but dominated by only diffusion process at low scan rates.