Controlled building of mesoporous MoS2@MoO2-doped magnetic carbon sheets for superior potassium ion storage

Abstract

Molybdenum disulfide (MoS₂) has attracted considerable attention as a candidate for potassium ion storage. However, the MoS₂ anode material is limited by its poor electron conductivity, poor structural stability due to large volume variation, growth of potassium dendrites and sluggish chemical kinetics. The combination of optimizing phase morphology, elemental composition, and surface nanostructure is effective for solving these problems. Herein, Fe was first encapsulated into the porous biomass-derived carbon during the Fe-catalysed post-annealing process. Subsequently, MoS₂@MoO₂ was well wrapped into the porous N-doped carbon matrix (CN) and the prepared MoS₂@MoO₂@Fe@CN was evaluated as an anode material for potassium ion batteries (KIBs). The growth mechanism of MoS₂@MoO₂@Fe@CN was thoroughly studied and the synthesis conditions were further explored. The good encapsulation of metallic Fe within the carbon framework and its intimate integration with the heterojunction of MoS₂@MoO₂ facilitate the transportation of electrons and ions, supplying favourable mass transfer. The low energy barrier for K⁺ insertion/extraction into the Mo–S–O and N–Mo–O channels is achieved primarily because of the finely incorporated heterojunction with elevated electron densities. Density functional theory (DFT) demonstrates that the internal electrical field guides the electron transfer from MoO₂ to MoS₂ at the interface, decreasing the K⁺ adsorption energy and migration barrier. This work supplies a new route to synthesize a heterojunction to enhance both the electrochemical performance and stability of MoS₂-based electrode material for effective energy storage.