Coupling MoSe 2 with Non-Stoichiometry Ni 0.85 Se in Carbon Hollow Nanoflowers for Efficient Electrocatalytic Synergistic Effect on Li-O 2 Batteries

Li-O batteries could deliver ultra-high theoretical energy density compared to current Li-ion batteries counterpart. The slow cathode reaction kinetics in Li-O batteries, however, limits their electrocatalytic performance. To this end, MoSe and Ni Se nanoflakes were decorated in carbon hollow nanoflowers, which were served as the cathode catalysts for Li-O batteries. The hexagonal Ni Se and MoSe show good structural compatibility with the same space group, resulting in a stable heterogeneous structure. The synergistic interaction of the unsaturated atoms and the built-in electric fields on the heterogeneous structure exposes abundant catalytically active sites, accelerating ion and charge transport and imparting superior electrochemical activity, including high specific capacities and stable cycling performance. More importantly, the lattice distances of the Ni Se (101) plane and MoSe (100) plane at the heterogeneous interfaces are highly matched to that of Li O (100) plane, facilitating epitaxial growth of Li O , as well as the formation and decomposition of discharge products during the cycles. This strategy of employing nonstoichiometric compounds to build heterojunctions and improve Li-O battery performance is expected to be applied to other energy storage or conversion systems.