Identifying the Evolution of Selenium‐Vacancy‐Modulated MoSe2Precatalyst in Lithium–Sulfur Chemistry

Abstract Witnessing compositional evolution and identifying the catalytically active moiety of electrocatalysts is of paramount importance in Li–S chemistry. Nevertheless, this field remains elusive. We report the scalable salt‐templated synthesis of Se‐vacancy‐incorporated MoSe 2 architecture (SeVs‐MoSe 2 ) and reveal the phase evolution of the defective precatalyst in working Li–S batteries. The interaction between lithium polysulfides and SeVs‐MoSe 2 is probed to induce the transformation from SeVs‐MoSe 2 to MoSeS. Furthermore, operando Raman spectroscopy and ex situ X‐ray diffraction measurements in combination with theoretical simulations verify that the effectual MoSeS catalyst could help promote conversion of Li 2 S 2 to Li 2 S, thereby boosting the capacity performance. The Li–S battery accordingly exhibits a satisfactory rate and cycling capability even with and elevated sulfur loading and lean electrolyte conditions (7.67 mg cm −2 ; 4.0 μL mg −1 S ). This work elucidates the design strategies and catalytic mechanisms of efficient electrocatalysts bearing defects.