In situ synthesis of an ultrafine heterostructural Nb2O5-NbC polysulfide promotor for high-performance Li-S batteries

Lithium-sulfur (Li-S) batteries are one of the most promising next-generation energy storage systems. Nevertheless, the notorious lithium polysulfide (LiPS) shuttle and sluggish sulfur redox kinetics result in inferior electrochemical performances, which are the major obstacles to their commercial application. Engineering the surface/interface of the ultrafine polysulfide promotor which can accelerate LiPS conversion and improve sulfur utilization is still challenging. Herein, we propose an effective strategy to synthesize ultrafine heterostructural Nb2O5-NbC homogeneously distributed in a carbon nanofiber matrix. Polystyrene (PS), as the nanocrystallite growth modulator, plays a vital role in suppressing particle agglomeration. The in situ formed heterostructures with a rational interface engineering design can achieve effective LiPS regulation and speed up the redox kinetics, as confirmed by the density functional theory (DFT) calculations and experimental characterizations. As expected, the battery containing ultrafine Nb2O5-NbC heterostructures delivers long-term cyclability with a low capacity decay of 0.044% per cycle over 800 cycles at 1.0C. And the decay rate is as low as 0.045% after 250 cycles at 0.5C with a sulfur loading of 4.0 mg cm(-2). This work provides a rational way to prepare ultrafine heterostructural polysulfide promotors via engineering the interface design for Li-S batteries.

Automated summary

This study proposes an effective strategy to enhance the performance of lithium-sulfur batteries by synthesizing ultrafine heterostructural Nb2O5-NbC distributed homogeneously in a carbon nanofiber matrix. Using polystyrene as a nanocrystallite growth modulator successfully suppresses particle agglomeration, forming in situ heterostructures that regulate lithium polysulfide effectively and speed up redox kinetics. The battery containing these heterostructures shows long-term stability with low capacity decay, even after hundreds of cycles at different discharge rates and sulfur loadings.