Experimental and Theoretical Study on rGO-Decorated Mo_2C Composite as the Anode Material for Lithium Ion Batteries

摘要

Transition-metal carbides are an emerging class of compounds which have been attracting attention due to their high electronic conductivity, capacity, and long life cycle. In the present work, an easy but facile synthesis method has been adopted to synthesize a Mo2C-based composite with free carbon and reduced graphene oxide (rGO) as an anode material for lithium-ion battery application. The nanosize Mo2C shortens the Li+ diffusion path, whereas rGO facilitates faster migration of electrons and cushions the developed stress due to lithiation and delithiation. The electrochemical performance improves drastically by the addition of just 1% carbon which further increases in the composite having rGO. The asdeveloped Mo2C/C/rGO composite exhibits a specific capacity as high as 630 mA h/g after 1600 cycles with nearly 100% efficiency. The material also delivers 198 mA h/g capacity at 4 A/g current density which again comes back to the normal state. The high capacitive current in the composite contributes to superior electrochemical performance. A full cell has been fabricated using LiNi0.6Mn0.2Co0.2O2 (NMC 622) and Mo2C/C/rGO as electrodes, which delivers around 114 mA h/g capacity at 50 mA/g. Theoretical calculations reveal that strong interaction of Mo2C and graphene induces modification of the geometrical (widening of Li movement channels) and electronic structures of Mo2C, which in turn improves the overall performance of the composite electrode.