In situ growth of 1T-MoS2 nanosheets on NiS porous-hollow microspheres for high-performance potassium-ion storage

In this study, a two-step route was adopted to in situ grow 1T-MoS2 nanosheets on NiS porous-hollow micro-spheres. It was found that the tiled MoS2 sheets tightly wrapped NiS spheres through coherent attachment via lattice-plane rotation, which would fully activate inert sulfur atoms on the basal plane of 1T-MoS2. This unique structure resembled a concentric spherical capacitor, which was able to store a large quantity of K+ ions with a capacity of 273.1 mAh/g at 5 A/g and deliver a stable capacity of 472.1 mAh g-1 after 1000 cycles at 0.2 A/g. In these multilevel hollow spheres, NiS phase mainly acted as a dielectric material to boost K-storage capability of MoS2 lamellae, and this electrical double-layer effect is more prominent either at high current densities or upon long-term cycling. It was anticipated that this work would shed new light on designing heterostructures of transition-metal dichalcogenides for high-performance potassium-ion storage.