Van der Waals heterostructure engineering by 2D space-confinement for advanced potassium-ion storage

Molybdenum disulfide (MoS₂) has received enormous attentions in the electrochemical energy storage due to its unique two-dimensional layered structure and relatively high reversible capacity. However, the application of MoS₂ in potassium-ion batteries (PIBs) is restricted by poor rate capability and cyclability, which are associated with the sluggish reaction kinetics and the huge volume expansion during K⁺ intercalation. Herein, we propose a two-dimensional (2D) space confined strategy to construct van der Waals heterostructure for superior PIB anode, in which the MoS₂ nanosheets can be well dispersed on reduced graphene oxide nanosheets by leveraging the confinement effect within the graphene layers and amorphous carbon. The strong synergistic effects in 2D van der Waals heterostructure can extremely promote the electron transportation and ions diffusion during K⁺ insertion/extraction. More significantly, the 2D space-confinement effect and van der Waals force inhibit polysulfide conversion product dissolution into the electrolyte, which significantly strengthens the structural durability during the long-term cycling process. As anticipated, the as-synthesized the "face-to-face" C/MoS₂/G anode delivers remarkable K-storage performance, especially for high reversible capacity (362.5 mAh·g^-1 at 0.1 A·g^-1), excellent rate capability (195.4 mAh·g^-1 at 10 A·g^-1) and superior ultrahigh-rate long-cycling stability (126.4 mAh·g^-1 after 4000 cycles at high rate of 5 A·g^-1). This work presents a promise strategy of structure designing and composition optimization for 2D layered materials in advanced energy storage application.