In-situ constructed accordion-like Nb2C/Nb2O5 heterostructure as efficient catalyzer towards high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have become one of the most promising next-generation battery systems. Nevertheless, Li-S batteries are still restricted by the dissolution and 'shuttling' of intermediate electrochemical products, lithium polysulfides (LiPSs), and the sluggish redox kinetics. Herein, we design a Nb2C/Nb2O5 heterostructure via water-steam etching at the first time to achieve fast trapping-diffusion-conversion of LiPSs by combining the trapping ability of Nb2C with catalytic activity of Nb2O5 toward LiPSs. The porous structure form in the water-steam etching process and the accordion-like structure can effectively contribute to the Li+ transportation enhancement. Nb2C nanosheets with high conductivity provide the basal planes for Nb2O5 contact, which suppresses the aggregation of Nb2O5 nanoparticles, leading to the overall structural and interface stabilization. In addition, the heterostructured interface ensures a rapid diffusion of anchored LiPSs. Benefiting from synergetic contributions of the above merits, Li-S batteries with the S-Nb2C/Nb2O5 electrode display a superior electrochemical performance with large initial discharge capacity of 844 mAh g-1 with a low capacity fading rate of only 0.05% per cycle during 500 cycles at 1.0 C. This work holds considerable instructive toward development of high-performance Li-S batteries.