Phase Transition Mechanism and Electrochemical Properties of Nanocrystalline MoSe2 as Anode Materials for the High Performance Lithium-Ion Battery

The real application of lithium-ion batteries in electric vehicles lacks the ideal anode materials. Herein, we report both experimental and theoretical study of MoSe2 nanocrystals as the anode materials. MoSe2 nanocrystals are successfully synthesized via a facile thermal-decomposition process. As the anode, the nanocrystalline MoSe2 yields the initial discharge and charge capacities of 782 and 600 mA h g–1 at the current of 0.1 C in a voltage of 0.1–3 V. First-principles simulation demonstrates that, during the initial discharge process, there is a Li atoms induced phase transition from 2H-MoSe2 to the O-MoSe2 phase at 0.9 V, and then Mo cluster occurs as more Li atoms intercalated into the MoSe2 lattice, which is associated with the formation of Mo and Li2Se. And the following charge/discharge processes are related to the conversion reaction between Mo and Li2Se. Meanwhile, the Li ion vacancy-hopping diffusion mechanism from octahedron to tetrahedron in MoSe2 lattice is proposed based on a quasi-2D energy favorable trajectory and the calculated diffusion constant is 1.31 × 10–13 cm2 s–1. For comparison, the amorphous MoSe2 demonstrates the same phase transition process after the initial charge/discharge cycle. The results show that the nanocrystalline MoSe2 can be the very promising novel anode materials for high performance Li-ion batteries.