Triggering Anionic Redox Activity in Li3NbS4 Through Cationic Disordering or Substitution

Extensive utilization of Li‐ion batteries for varieties of applications necessitates ceaseless improvements of electrode materials for achieving higher energy density. Towards this goal, Li‐rich layered oxides exhibiting high capacity due to cumulated cationic and anionic redox activities are under study for nearly a decade. Still, several unanswered questions remain with respect to these Li‐driven anionic redox reactions in terms of the activation process and long‐term consequences upon cycling. Here, the Li‐rich Li3NbS4 phase is focused, and synthesized as two different polymorphs, namely ordered and disordered phases. From analyses of their chemical and electrochemical properties, a crystal‐electronic structure relationship is unraveled that triggers the anionic redox activity in these compounds. Moreover, through complementary theoretical calculations, the capability of cationic disorder to trigger anionic redox activity via the hybridization of cationic and non‐bonding anionic energy levels is shown. This finding is further supported by the appearance of anionic redox activity by introducing the disorder through cationic substitution. Altogether, the insights derived can help in designing new anionic redox materials with optimum performances for practical applications. This work explains the key structural phenomenon that triggers the anionic redox property in Li‐rich transition metal oxides having d0 transition metal ion. The order and disorder polymorph of Li3NbS4 where the cation disordering achieved by either synthesis method or by electrochemical lithiation/ de‐lithiation triggers S2–/Sn– anionic redox property and enable high capacity lithium‐ion battery electrodes are explored.