Boosting sodium storage performance of Mo2C via nitrogen-doped carbon sphere encapsulation and rGO wrapping

Abstract

As a model compound for transition metal carbides, Mo2C is considered as a promising anode material for sodium ion batteries (SIBs) due to its excellent electrical conductivity and low Na+ diffusion barriers. However, the low capacity and poor rate capability strongly limit its practical applications. Nanostructuralization of active materials combined with conductive matrix incorporation may address this issue. Inspired by this concept, we herein propose a rational strategy to create a special structure with ultrafine Mo2C nanoparticles encapsulated in porous N-doped carbon spheres wrapped by rGO. The well-defined double-carbon coating effectively limited the growth/agglomeration of Mo2C and provided highly conductive network to stabilize capacity. Theoretical calculations disclose hetero-interaction between components favorably promoted Na+ diffusion kinetics. Impressively, such composite with excellent cyclic stability showed a record high reversible capacity (332.9 mA h/g at 0.1 A/g) and rate capability (155.7 mA h/g at 5 A/g) of Mo2C based materials for SIBs.