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

Abstract 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 (Li_0.33VS₂, LiVS₂, Na_0.5VS₂, NaVS₂, K_0.6VS₂, K_zVS₂, 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.