Mediating the redox kinetics of polysulfides is a promising strategy to mitigate the shuttling and sluggish conversion of polysulfides for practical application of lithium-sulfur (Li-S) batteries. Herein, novel TiH2 nanodots (THNDs) fabricated by sonication-assisted liquid-phase exfoliation are used as bifunctional electrocatalysts for Li-S batteries. Both experimental and theoretical results reveal that THNDs can not only provide a strong chemical affinity to polysulfides but also bidirectionally promote the precipitation/decomposition of Li2S from/to polysulfides during the discharge/charge process, thus effectively suppressing the shuttle effect and improving the redox kinetics of polysulfides. Owing to these advantages accompanied by the abundant catalytically active sites of THNDs, the assembled Li-S batteries deliver a low capacity fading rate of 0.055% per cycle over 1000 cycles at 1C and a high areal capacity of 5.38 mAh cm-2 after 50 cycles with a high sulfur loading of 8.5 mg cm-2. This work demonstrates the great potential of utilizing functional metal hydrides as effective electrocatalysts for Li-S batteries, which will incite more investigation into the specific selection of metal compounds to boost the redox kinetics of polysulfides.
Keywords: Li−S batteries; TiH2 nanodots; bifunctional electrocatalyst; redox kinetics; shuttle effect.