Boosting the potassium-ion storage performance enabled by engineering of hierarchical MoSSe nanosheets modified with carbon on porous carbon sphere

Developing suitable electrode materials capable of tolerating severe structural deformation and overcoming sluggish reaction kinetics resulting from the large radius of potassium ion (K+) insertion is critical for practical applications of potassium-ion batteries (PIBs). Herein, a superior anode material featuring an intriguing hierarchical structure where assembled MoSSe nanosheets are tightly anchored on a highly porous micron-sized carbon sphere and encapsulated within a thin carbon layer (denoted as Cs@MoSSe@C) is reported, which can significantly boost the performance of PIBs. The assembled MoSSe nanosheets with expanded interlayer spacing and rich anion vacancy can facilitate the intercalation/deintercalation of K+ and guarantee abundant active sites together with a low K+ diffusion barrier. Meanwhile, the thin carbon protective layer and the highly porous carbon sphere matrix can alleviate the volume expansion and enhance the charge transport within the composite. Under these merits, the as-prepared Cs@MoSSe@C anode exhibits a high reversible capacity (431.8 mAh g-1 at 0.05 A g-1), good rate capability (161 mAh g-1 at 5 A g-1), and superior cyclic performance (70.5% capacity retention after 600 cycles at 1 A g-1), outperforming most existing Mo-based S/Se anodes. The underlying mechanisms and origins of superior performance are elucidated by a set of correlated in-situ/ex-situ characterizations and theoretical calculations. Further, a PIB full cell based on Cs@MoSSe@C anode also exhibits an impressive electrochemical performance. This work provides some insights into developing high-performance PIBs anodes with transition-metal chalcogenides.