Vacancy-Induced In Situ Topotactic Transformation of MoS₂ for Enhanced Polyselenide Catalytic Conversion

Vacancy engineering has emerged as an efficient approach for constructing high-performance electrocatalysts to enhance lithium polyselenides (LiPSes) adsorption and conversion in lithium-selenium (Li-Se) batteries. However, the catalytic mechanisms of vacancies remain one-sided because of the insufficient understanding of the dynamic evolution of electrocatalysts during reactions. Herein, by leveraging MoS₂ with sulfur vacancies (SVs-MoS₂) as a model electrocatalyst, the phase reconstruction of defective electrocatalysts during LiPSes redox reactions, and the essence of enhanced electrocatalytic activity are unveiled. As validated by comprehensive experimental characterizations and theoretical calculations, the interaction between LiPSes and SVs-MoS₂ is demonstrated to induce the in situ topotactic transformation from SVs-MoS₂ to MoSSe. This compositional evolution affords an optimized d-p orbital hybridization, which not only facilitates the intrinsic charge transfer but also activates the basal-plane catalytic activity though the electron-rich Se sites, thereby expediting the LiPSes redox kinetics. Benefitting from these advantages, the Li-Se batteries assembled with SVs-MoS₂ exhibit an outstanding capacity retention and cycling stability at a wide temperature range (-10-40 °C). This work sheds light on the topotactic reconstruction of defective electrocatalysts during the electrochemical reactions, which helps attain the fundamental understanding and extend the applications of vacancy engineering in electrocatalysis.