Titanium nitride nanocrystals anchored evenly on interconnected carbon nanosheets with effective chemisorption and catalytic effects towards polysulfides for long-life lithium−sulfur batteries

Abstract

The “shuttle effect” of lithium polysulfides (LiPSs) and sluggish redox reactions limit the application of Li−S batteries. In this study, titanium nitride (TiN) nanocrystals merely and evenly anchored on carbon nanosheets (TiN@CNs) are prepared by heat treating TiO2@CNs in flowing ammonia. TiN nanoparticles do not accumulate in places without CNs, which can alleviate volume expansion in cycling process. CNs with high conductivity and a large specific surface area can accelerate Li+ and electron transportation and accommodate a higher sulfur content. Moreover, TiN nanocrystals can effectively anchor polysulfides and accelerate the redox reaction, which can be explained by the adsorption experiment of LiPSs, X-ray photoelectron spectroscopy, and theoretical calculations. Thus, the TiN@CNs-2/S cathode delivers an initial capacity of 1273 mAh g−1 and remains at 908 mAh g−1 after 100 cycles for 0.5 A g−1. For the long-term cycle performance, the cathode exhibits a slow capacity decay rate of 0.035% per cycle over 1000 cycles at 2 A g−1. This novel structure has potential in the design of advanced performance Li−S batteries.