Studies on the influence of weight percentage of multiwalled carbon nanotubes in Mn/Ni/Co nanocomposites for hybrid supercapacitors

Abstract

In this work, four composites of varied percentage of multiwalled carbon nanotubes (MWCNTs) with Mn, Ni, and Co oxide nanoparticles (TMO) were prepared by hydrothermal process and abbreviated as MNC-1, MNC-2, MNC-3 and MNC-4. The prepared materials were characterized for their physico-chemical properties by Powder XRD, SEM, TEM, BET, XPS, FT-IR and Raman analytical techniques. The electrochemical properties of the composites were evaluated in a three-electrode system incorporating the composite as the working electrode. Among the nanocomposites investigated, the MNC-3 sample with the TMO and MWCNTs ratio of 1: 0.25 showed lowest surface area, pore volume and pore diameter. Further, this sample exhibited highest specific capacitance of 985 F/g at 2 mV/s by cyclic voltammetry in 1 M KOH solution. This material when checked for its stability at high current density of 15 A/g for 5,000 cycles, showed 83% capacitance retention which subsequently changed to 70% after 10,000 cycles. An asymmetric supercapacitor device was designed using MNC-3 as the positive electrode and a commercial activated carbon as negative electrode. The device exhibited significant specific capacitance, energy density and power density values of 58 F/g, 17 Wh/kg, and 1768 W/kg, respectively. A life cycle test conducted for the fabricated device at a current density of 15 A/g showed capacitance retention of 78% even after 10,000 cycles. The practical application of the device was checked and demonstrated by powering two red LEDs connected in series for 12 mins.