Hollow MoS2 Spheres Confined in Carbon Fibers for Ultralong-life Potassium Storage

Potassium-ion energy storage systems are gradually showing their status due to abundant potassium resources and low cost. Unfortunately, K+ storage materials are still an exigent issue due to the large radius and sluggish kinetics of K+. Herein, a composite electrode (H-MoS2@CNFs) built by electrospun carbon fibers (CNFs) as the frame and the hollow MoS2 spherical shell as the inner core is designed. H-MoS2@CNFs is endowed with the following preponderance: the outside CNFs interlocked with the MoS2 nanosheets play a triple role in conducting electrons, buffering the volume expansion of MoS2, and maintaining the structural stability of the electrode; the exposed edges of the (002) plane of MoS2 nanosheets in direct contact with the electrolyte stored in the internal cavity facilitate the K+ reaction kinetics. As the anode of potassium- ion batteries, H-MoS2@CNFs delivers an excellent cyclic performance (187.7 mAh g(-1) at 2.0 A g(-1) after 5000 cycles with 0.0037% decay per cycle) and high rate capability (184.7 mAh g(-1) at 10.0 A g(-1)). Furthermore, owing to the superior potassium storage and freestanding characteristics without the binder and conductive additives, the potassium-ion capacitor (PIC) based on the anode exhibits a high energy density of 165 Wh kg(-1) at a power density of 378 W kg(-1), which furnishes a reliable basis for the development of two-dimensional materials for the PIC.

Automated summary

Potassium-ion energy storage systems are gaining importance due to abundant potassium resources and low cost. However, the development of potassium-ion storage materials remains a challenging issue. In this study, a composite electrode called H-MoS2@CNFs is designed with carbon fibers as the frame and hollow MoS2 spherical shell as the inner core. This electrode demonstrates superior performance in terms of cyclic performance and rate capability for potassium-ion batteries, as well as high energy density for potassium-ion capacitors.