Facile hydrothermal synthesis of MoS2 nano-worms-based aggregate as electrode material for high energy density asymmetric supercapacitor

Abstract

Nowadays, supercapacitors and batteries are trending electrochemical energy storage devices. However, their low energy density and uncertain power density limited their applications, respectively. Recently, the latest innovation in energy storage devices, called hybrid supercapacitors, has appeared as an eventual energy storage device that demonstrates a hybrid storage mechanism of both supercapacitors and batteries. In this work, MoS2 has been prepared by the facile hydrothermal method, characterized by different techniques, and applied as an electrode in supercapacitors and supercapatteries. The XRD patterns and EDX confirm the successful synthesis of MoS2 with an average crystallite size of 62.25 nm, while the SEM images show the randomly oriented nanoworms of MoS2. The XPS spectrum depicts the presence of variable oxidation states of molybdenum (Mo4+and Mo6+) in the MoS2. The electrochemical performance shows that the highest specific capacitance and specific capacity reached 1866.66 F/g and 1119.99 C/g, respectively, at a scan rate of 5 mV/s for MoS2. The asymmetric supercapacitor device is made from (Graphite/MoS2) using as a working electrode and activated carbon as a cathode, which are separated by filter paper. Furthermore, the Dunn's model is utilized to evaluate of capacitive and battery mechanisms and shows the dominant role of diffusive and surface-controlled developments at low and high scan rates, respectively, owing to the change in diffusion time of electrolyte species. The fabricated device shows an energy density and power density of 103.51 Wh/kg and 3807.59 W/kg at a current density of 1 and 7 A/g, respectively, with 93.52% capacity stability and 99.8% coulombic efficiency. This excellent performance of MoS2 is believed to be a potential electrode candidate for asymmetric supercapacitor applications.