Exceptional interfacial electrochemistry of few-layered 2D MoS2 quantum sheets for high performance flexible solid-state supercapacitors

Abstract

Molybdenum disulfide (MoS₂) is one of the promising electrochemical energy storage materials among the recently explored 2D materials beyond the extensively studied graphene sheets. However, MoS₂ in the form of quantum sheets (QSs) has not yet been examined for use in energy storage devices (batteries and supercapacitors). Here, we demonstrate the superior electrochemical charge-storage properties of exfoliated MoS₂ QSs (with lateral size in the range of 5 to 10 nm) for the first time. A salt-assisted ball milling process was used to prepare MoS₂ QSs in gram scale that leads to size confinement in both lateral and vertical orientations. The electrochemical analysis of MoS₂ QSs indicated their superior capacitive properties compared to the bulk MoS₂, which originates from the combination of quantum capacitance and electrochemical capacitance. The device specific properties of MoS₂ QSs were studied by constructing a flexible symmetric supercapacitor (SSC) that demonstrated a high device capacitance (162 F g⁻¹), energy density (14.4 Wh kg⁻¹), good rate capability, and long cycle life. The energy storage performance metrics of MoS₂ QSs based SSC device were superior compared to the state-of-art MoS₂ based supercapacitors. Furthermore, a solar-driven wireless charging power system comprising the fabricated MoS₂ QSs-based SSC as an energy storage device is illustrated in the view of expanding its utility towards practical applications.