Combined High Catalytic Activity and Efficient Polar Tubular Nanostructure in Urchin-Like Metallic NiCo2Se4 for High-Performance Lithium-Sulfur Batteries

Urchin-shaped NiCoSe (u-NCSe) nanostructures as efficient sulfur hosts are synthesized to overcome the limitations of lithium-sulfur batteries (LSBs). u-NCSe provides a beneficial hollow structure to relieve volumetric expansion, a superior electrical conductivity to improve electron transfer, a high polarity to promote absorption of lithium polysulfides (LiPS), and outstanding electrocatalytic activity to accelerate LiPS conversion kinetics. Owing to these excellent qualities as cathode for LSBs, S@u-NCSe delivers outstanding initial capacities up to 1403 mAh g at 0.1 C and retains 626 mAh g at 5 C with exceptional rate performance. More significantly, a very low capacity decay rate of only 0.016% per cycle is obtained after 2000 cycles at 3 C. Even at high sulfur loading (3.2 mg cm), a reversible capacity of 557 mAh g is delivered after 600 cycles at 1 C. Density functional theory calculations further confirm the strong interaction between NCSe and LiPS, and cytotoxicity measurements prove the biocompatibility of NCSe. This work not only demonstrates that transition metal selenides can be promising candidates as sulfur host materials, but also provides a strategy for the rational design and the development of LSBs with long-life and high-rate electrochemical performance