Tailored MoS2 bilayer grafted onto N/S-doped carbon for ultra-stable potassium-ion capacitor

Abstract

Few-layers MoS2-based materials have a comprehensive advantage in accommodating potassium-ions due to the rich active S-Mo-S sites and rapid ionic dynamics. Unfortunately, the serious self-stacking of MoS2 molecular layer resulted in insufficient space to buffer the stress/strain caused by K-ions intercalation, which makes MoS2-based electrode exhibits low capacitance and poor cyclic stability in practical studies. To solve this, an in situ induced deposition strategy is proposed to construct a MoS2/C hybrid (labelled as NS-C@b-MoS2). In this NS-C@b-MoS2 hybrid, the MoS2 molecular with bilayer structure is grafted onto a 3D N/S dual-doping carbon skeleton in one spatial-chemical doubly confined mode. This unique hybrid mode not only expose more S-Mo-S bonds to adsorb K-ions, but also avoid the structural collapse of electrode by spatial-chemical doubly confinement effect of carbon skeleton. Consequently, the resultant NS-C@b-MoS2 anode delivers a high specific capacity of 451.2 mAh g−1 at 0.1 A g−1 and an ultra-long cycle stability up to 20,000 cycles with only 0.0013 % fading per cycle. Moreover, the assembled NS-C@b-MoS2//NSAC potassium-ion capacitor delivers a high energy density of 126.5 Wh kg−1 and retains 55.2 Wh kg−1 after 65,000 cycles at 3800 W kg−1, which over the state-of-the-art reported performance.