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