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

VS2 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 VS2 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 (Li0.33VS2, LiVS2, Na0.5VS2, NaVS2, K0.6VS2, KzVS2, z > 0.6) during the discharging/charging processes are identified, indicating that VS2 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 VS2 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. The intermediates and final products produced at the VS2 cathode during the discharging/charging processes in alkali metal‐ion batteries are identified. VS2 enables partially irreversible Li+ storage and wholly reversible storage of Na+/K+. A more complex phase transition process and the highest energy barrier for the diffusion of Na+ in sodium‐ion batteries than the other two systems are discovered.