Ultrathin MoSe 2 @N-doped carbon composite nanospheres for stable Na-ion storage.

Two-dimensional transition metal dichalcogenides are widely studied as anode materials for metal ion batteries. This application requires high electric conductivity which can be achieved by forming composites with conductive carbon. In this work, we demonstrate the creation of nanospheres composed of Mo-based thin nanosheets (MoS2 , MoSe2 and Mo2 C) uniform embedded within a N-doped carbon matrix. Using MoSe2 /N-doped carbon nanospheres as an example, we investigate in detail the electrochemical property in Na ion storage and reveal the advantage over previously reported MoSe2 electrodes (higher capacity and improved capacity retention up to 500 cycles). Furthermore, we provide evidence by ex situ x-ray diffraction to the nominal irreversible conversion reaction during the first discharge.