Molybdenum Disulfide (MoS2) and Its Nanocomposites as High-Performance Electrode Material for Supercapacitors

Abstract

Supercapacitor is a promising energy storage device, which has many advantages including long service lifetime, great power density, fast charge-discharge processes, and green environmental protection. The properties and performance of supercapacitors are greatly dependent on the electrode materials; hence the selection of the electrode material is crucial. There are many metal oxides which have been reported for supercapacitors and ultracapacitors; however, its performance is not that as expected. Thus high-performance electrode materials with large surface area and specific capacitance have been a topic of interest for the development of high-performance supercapacitors. Recently, two-dimensional (2D) transition metal dichalcogenides having layered structures, such as MoS2, VS2, SnS2, CoS2, and WS2, have received significant attention because they offer good energy density, power density, and cycling stability. Among them, the layered molybdenum disulfide (MoS2) is considered to have great potential for its applications as supercapacitors. MoS2 nanosheet is composed of one Mo atomic layer sandwiched between two S layers by covalent bonding, and with these triple layers stacked together to form a layered structure, is expected to act as an excellent energy storage material. It is because of the 2D electron–electron correlations among Mo atoms which would aid in enhancing planar electric transportation properties. MoS2 nanosheets can deliver excellent pseudocapacitance because of the Mo ions having oxidation states ranging from +2 to +6, which enable them to be used as high-performance electrode materials in supercapacitors. Indeed, as a graphene analogue, MoS2 nanosheets exhibit unique physical, optical, and electrical properties correlated with its 2D ultra-thin atomic layer structure and high surface area, making it very interesting for its use as electrodes in high-performance supercapacitors and also a promising supporting material to stabilize metal nanoparticles (NPs), forming hierarchical composites. The specific capacitance of MoS2 is still very limited in alone for energy storage applications. The combination of MoS2 and other conducting materials such as graphene, carbon nanotubes (CNTs), or ceramic nanomaterials such a zirconium (Zr) may overcome these deficiencies. This chapter gives a clear picture of the applications of MoS2 as high-performance electrode in supercapacitors.