Flexible MoSe2/MXene films for Li/Na-ion hybrid capacitors

MoSe2 presents a prospect in sodium-ion capacitors (SICs) and lithium-ion capacitors (LICs), which are considered as promising new energy systems because they possess the merits of both batteries and supercapacitors. In this work, we develop a flexible and free-standing MoSe2/MXene film with sandwich structure as an anode for SICs and LICs. The highly conductive MXene sheets can boost the electrochemical activity of MoSe2 nanoparticles. Meanwhile, the MoSe2 nanoparticles can also enlarge the interlayer spacing of MXene film, facilitating the permeation of electrolyte and eventually leading to fast reaction kinetics of MoSe2. The sandwich structure can effectively limit the loss of intermediate products generated during the insertion/extraction reactions of MoSe2, giving rise to a durable cycle performance. The MoSe2/MXene film with an optimized mass ratio exhibits much improved Li/Na storage performances as compared with the pristine MoSe2, particular the long term cyclic stability. SICs and LICs could deliver high energy/power densities (Max 110.1 Wh kg(-1)/4764.7 W kg(-1) and 84.9 Wh kg(-1)/3288.3 W kg(-1), respectively), as well as long lifespans, demonstrating the prospective of such MXene/MoSe2 film electrode towards alkali metal ion capacitors. Assembled flexible SICs/LICs prototypes further prove the potential application for the future flexible energy storage devices.