Conversion of MoS2 to a Ternary MoS2–xSex Alloy for High-Performance Sodium-Ion Batteries

MoS 2 has attracted tremendous attention as an anode for Na-ion batteries (NIBs) owing to its high specific capacity and layered graphite-like structure. Herein, MoS 2 is converted to a ternary MoS 2– x Se x alloy through the selenizing process in order to boost the electrochemical performance for Na-ion batteries. Conversion of MoS 2 to MoS 2– x Se x expands interlayer spacing, improves electronic conductivity, and creates more defects. The expanded interlayer spacing decreases Na + diffusion resistance and facilitates Na + fast transfer. The integrated graphene as a conductive network offers effective pathway for electron migration and maintains structural stability of electrodes during cycles. The ternary MoS 1.2 Se 0.8 /graphene (MoS 1.2 Se 0.8 /G) electrode demonstrates an extremely high reversible capacity of 509 mA h g –1 after 200 cycles at 0.1 A g –1 (capacity retention of 109%) as an anode for sodium-ion batteries. Even at 2 A g –1 and after 700 cycles, the MoS 1.2 Se 0.8 /G electrode also displays a relatively high reversible capacity of 178 mA h g –1 . Full cells assembled with Na 3 V 2 (PO 4 ) 2 F 3 cathodes and MoS 1.2 Se 0.8 /G anodes reveal high charge/discharge capacities. This work demonstrates that the ternary MoS 2– x Se x alloy could be a potential anode material for Na-ion storage.