Robust and Conductive Red MoSe<sub>2</sub> for Stable and Fast Lithium Storage

Two-dimensional (2D) layered transition-metal dichalcogenides (LTMDs) display various crystal phases with distinct symmetries, structures, and physical properties. Exploring and designing different structural phases in two dimensions could provide an avenue for switching material properties, aiming at practical applications for potential fields. Here we demonstrate a conceptually designed approach to narrow the band gap of MoSe<sub>2</sub> and obtain a conductive red MoSe<sub>2</sub> nanosheet. By introducing the high valence state of Mo species and constructing the Mo–O bonding on the surface of the MoSe<sub>2</sub> nanosheets, the electronic properties can be modified and the conductivity is accordingly improved, an effect that significantly improves their lithium storage capacity and high-rate capability. We anticipate that the exploration of the conductive red MoSe<sub>2</sub> with tunable band gap could help us unlock more potential crystal structures of LTMD-based and even other 2D materials for further applications.