Preparation and performance evaluation of N-rGO/Mo2C heterostructures as sulfur hosts for lithium-sulfur batteries.

Abstract

The practical application of lithium-sulfur batteries is greatly restricted by the migration of soluble polysulfide intermediates, dramatic electrode volume fluctuations, and slow sulfur conversion reactions. Herein, a new sulfur host material was developed by uniformly decorating nitrogen-doped reduced graphene oxide with molybdenum carbide nanoparticles (N-rGO/Mo2C). Furthermore, compared with pristine rGO, nitrogen doping increases the active sites for lithium polysulfide adsorption on rGO. The key innovation lies in the synergistic combination of highly conductive N-rGO and polar Mo2C with strong chemisorption and electrocatalytic activity. Owing to the synergistic adsorption-catalysis effect, the N-rGO/Mo2C/S electrode exhibits remarkable electrochemical behavior, including large reversible capacity, excellent high-rate capability, and durable cycling stability. Furthermore, the effects of different Mo2C contents on lithium-sulfur battery behavior were systematically investigated. The optimally proportioned N-rGO/Mo2C composite (NRM-300) delivered a specific capacity of 483.6 mAh g-1 after 500 long-term cycles at a current density of 2C, with a capacity decay rate of only 0.0574% per cycle. Even at an areal loading of 3.6 mg cm-2, an areal capacity of 2.87 mAh cm-2 is still retained after 100 cycles at a current density of 0.2C. A feasible route for constructing efficient lithium-sulfur battery cathodes is presented in this work by integrating conductive frameworks with polar catalytic components.