Insights into the Storage Mechanism of Layered VS2 Cathode in Alkali Metal‐Ion Batteries

Abstract VS 2 is one of the attractive layered cathodes for alkali metal‐ion batteries. However, the understanding of the detailed reaction processes and energy storage mechanism is still inadequate. Herein, the Li + /Na + /K + insertion/extraction mechanisms of VS 2 cathode are elucidated on the basis of experimental analyses and theoretical simulations. It is found that the insertion/extraction behavior of Li + is partially irreversible, while the insertion/extraction behavior of Na + /K + is completely reversible. The detailed intermediates and final products (Li 0.33 VS 2 , LiVS 2 , Na 0.5 VS 2 , NaVS 2 , K 0.6 VS 2 , K z VS 2 , z > 0.6) during the discharging/charging processes are identified, indicating that VS 2 undergoes different phase transitions and solid–solution reactions in different battery systems, which have a great influence on the battery performance. Moreover, the diffusion of Na + in VS 2 cathode is demonstrated to be much slower than that of Li + and K + . Such mechanistic research provides a reference for in‐depth understanding of energy storage in layered transition metal sulfides/selenides.