MoSe ₂ @CNT Core–Shell Nanostructures as Grain Promoters Featuring a Direct Li ₂ O ₂ Formation/Decomposition Catalytic Capability in Lithium‐Oxygen Batteries

For lithium-oxygen batteries (LOBs), the strong oxidant intermediate and byproducts during the charge/discharge process are the main reasons for the degradation of the electrochemical performance. Searching for highly efficient catalysts for the direct formation/decomposition of Li2O2 is essential for the development of LOBs. In this study, core–shell nanostructured MoSe2@CNT with uniform MoSe2 coating layers are purposefully synthesized through a facile hydrothermal strategy to address the negative intermediate and side-product issues, therefore enhancing the battery performance. The continuous and multiwalled MoSe2 layers can not only work as grain promoters that induce the initial nucleation and growth of equiaxed Li2O2 grains on the cathode surface even under a high rate, but also prevent the byproducts formation from corrosive issues between carbon and electrolyte. Moreover, density functional theory (DFT) calculations reveal the intrinsic layer dependent direct formation/decomposition catalytic capability of 2D MoSe2 and the LiO2 avoidable reaction pathway during the discharge/charge process, theoretically revealing the direct epitaxial growth mechanisms of Li2O2. As a consequence, the MoSe2@CNT cathode exhibited a superior specific capacity over 32 000 mAh g−1, excellent rate capabilities, and ultralong cycle life of 280 cycles at a high rate of 500 mA g−1.