The Key Role of N/S Codoped Carbon Dots in Efficient Capture and Conversion of Lithium Polysulfides.

Abstract

The dissolution and shuttle of lithium polysulfides (LiPSs) should be primarily responsible for rapid capacity decay in lithium-sulfur batteries (LSBs), which severely limits sulfur utilization. Introduction of cathode additives that can immobilize and rapidly convert LiPSs has been identified as effective in alleviating the shuttle effect. In this study, N/S codoped carbon dots (NSCDs) have been synthesized via a typical hydrothermal method, whose surfaces are rich in polar functional groups (─COOH, ─OH, ─SO_3, and ─NH₂) to capture LiPSs and effectively modulate the deposition behavior of Li₂S. NSCDs as an additive of cathode significantly improve the battery discharge capacity and cycle life that it could deliver a reversible specific capacity of 1207.2 mAh g^-1 at a current density of 0.2 C and stably operate for over 400 cycles at 1 and 2 C current densities. This work provides valuable insights into the application of 0D carbon nanomaterials in the field of LSBs.