S, N-codoped carbon capsules with microsized entrance: Highly stable S reservoir for Li-S batteries

Nanostructured carbon materials are extensively applied as host materials to improve the utilization rate and reversibility of elemental sulfur in lithium sulfur (Li-S) batteries. Here, S, N-codoped carbon capsules (SNCCs) with microporous walls, prepared by a self-assembly process, are used as the sulfur host material in Li-S batteries. The SNCCs provide plenty of micron-sized cavities to accommodate a high S loading, which are sealed by thick walls with microsized entrance to efficently suppress the shuttle effect of lithium polysulfides. As the cathode in Li-S battery, the SNCCs/sulfur composite with a sulfur mass loading of 70 wt% exhibits a high average reversible capacity of 1220 and 1116 mA h g(-1) at 0.5C and 1C, respectively, superior rate performance (905 and 605 mAh g(-1) at 5C and 10C, respectively) and excellent cycling stability (capacity fading rate of 0.03% per cycle in 500 cycles). Even at a high sulfur areal loading of 7.3 mg/cm(2), the SNCCs/0.7S electrode still deliver a high initial discharge capacity of 838 mAh g(-1) and keeps at 730 mAh g(-1) after 100 cycles, corresponding to an extraordinary capacity retention of 87.1%, showing an excellent cyclic stability. The outstanding electrochemical performance is associated with the unique capsule structure with abundant volume, microsized entrance and high conductivity. Our results provides a new strategy to prepare highly stable sulfur-carbon composites for the application in Li-S batteries. (C) 2021 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Automated summary

Nanostructured carbon materials are widely used as host materials for improving the performance of elemental sulfur in Li-S batteries. S, N-codoped carbon capsules (SNCCs) with microporous walls are used as the sulfur host material, providing high sulfur loading capacity, efficient suppression of shuttle effect, and exhibiting outstanding electrochemical performance.