Towards Sustained Sulfide Conversion: Cation Defect Engineering in Fe ₂ Mo ₃ O ₁₂ Electrocatalysts

A novel iron molybdate (Fe 2 Mo 3 O 12 ) catalyst engineered with cationic defects was designed and prepared to address critical challenges in lithium–sulfur (Li–S) batteries. By optimizing the concentration of Fe defects, the electronic structure of the catalyst was tailored, the catalytic activity was enhanced, and the dynamic surface reconstruction was promoted during cycling. This process facilitates the in situ formation of a metastable FeS x phase. This phase serves as a transient active interface for efficient polysulfide conversion and regenerates during charging. This regenerative mechanism prevents catalyst passivation, ensuring long‐term electrochemical stability. Li–S batteries with the Fe‐deficient catalyst (FMO‐500) deliver a remarkable specific capacity of 807 mAh g −1 at a high rate of 5C, maintaining a minimal decay rate of 0.023% per cycle over 1800 cycles. This work provides deep insights into defect‐mediated catalytic mechanisms and promotes the development of efficient, long‐lasting Li–S batteries.