Flexible and binder-free supercapacitor electrode with high mass loading using transition metal doped MoS2 nanostructures

Abstract

Transition metal (TM) doping has been done on MoS2 to activate its inactive sites. The edge sites created on doping with nickel (Ni), cobalt (Co), and iron (Fe) provide a conductive, flexible, and binder-free electrode with high mass loading (>19 mg/cm2) over carbon cloth. The vertical flower-like morphology together with the presence of dangling bonds, imparts a high rate of adsorption and desorption process and outstanding super-capacitive properties. Due to the identical ionic radii, Ni atom will effectively replace the Mo atoms in MoS2 and also intercalate between the layers. The resultant lattice distortions, and the presence of Ni atom in the interstitial sites, provide faradaic and non-faradaic capacitance to the Ni-doped electrode, (Ni-MoS2/CC), giving it an excellent specific capacitance of 305.9 F/g compared to 170.2 F/g for the pure MoS2/CC electrode. The doping produced 180% increase in the specific capacitance of MoS2, which is the highest reported value for a high mass loading electrode. There is an enhancement in the properties of TM doped MoS2 electrodes prepared in the present study as binders and conductive additives are avoided. A symmetric supercapacitor developed using the Ni-MoS2/CC electrode gave a specific gravimetric capacitance of 50 F/g, energy density of 4.4 W h/kg, and power density of 79.1 W/kg at a current density of 0.5 A/g. The device retained 87.4% capacitance after 5000 cycles at a scan rate of 1 A/g.