Te doped 1T/2H-MoSe2 nanosheets with rich defects as advanced anode materials for high-rate sodium ion half/full batteries

MoSe2 with a two-dimensional layer-like structure has been considered a promising anode material for sodium-ion batteries (SIBs) on account of its high capacity and rich reserves on Earth. However, the inherent low conductivity of 2H-MoSe2, as well as the inevitable volume fluctuation during cycling, causes structural collapse and capacity decline, resulting in poor rate capability and unacceptable cycling stability. To improve the sodium storage properties of 2H-MoSe2, the Te doping strategy has been adopted to successfully synthesize Te doped 1T/2H-MoSe2 nanosheets (Te-MoSe2) via a facile two-step reaction. The Te doping induces the phase transition of 2H-MoSe2 to form 1T-MoSe2, which can improve the electron conductivity and generate more active sites, benefiting the promotion of sodium storage capacity. Besides, the 1T/2H heterogeneous interface accelerates the charge transfer kinetics. Thus, as an innovative anode material for sodium-ion half batteries, Te-MoSe2 exhibits better sodium storage performances than pure MoSe2. The full batteries composed of the Te-MoSe2 anode and Na3V2(PO4)3@rGO cathode also deliver remarkable electrochemical performances. The related kinetics results confirm the excellent electron transfer efficiency and rapid Na+ diffusion behavior of Te-MoSe2. Moreover, the reaction mechanism has also been elucidated by some ex situ characterization techniques. The good reversibility and excellent sodium storage properties of the Te-MoSe2 electrode indicate its potential application in future energy storage fields.