Hierarchically porous, ultrathin N-doped carbon nanosheets embedded with highly dispersed cobalt nanoparticles as efficient sulfur host for stable lithium-sulfur batteries

The sluggish redox kinetics and shuttle effect of soluble polysulfides intermediate primarily restrict the electrochemical performance of lithium-sulfur (Li-S) batteries. To address this issue, rational design of high-efficiency sulfur host is increasingly demanded to accelerate the polysulfides conversion during charge/discharge process. Herein, we propose a macro-mesoporous sulfur host (Co@NC), which comprises highly dispersed cobalt nanoparticles embedding in N-doped ultrathin carbon nanosheets. Co@NC is simply synthesized via a carbon nitride-derived pyrolysis approach. Owing to the highly conductive graphene-like matrix and well defined porous structure, the designed multifunctional Co@NC host enables rapid electron/ion transport, electrolyte penetration and effective sulfur trapping. More significantly, N heteroatoms and homogeneous Co nanocatalysts in the graphitic carbon nanosheets could serve as chemisorption sites as well as electrocatalytic centers for sulfur species. These Co-N active sites can synergistically facilitate the redox conversion kinetics and mitigate the shuttling of polysulfides, thus leading to improved electrochemical cycling performance of Li-S batteries. As a consequence, the S/Co@NC cathode demonstrates high initial specific capacity (1505 mA h g(-1) at 0.1 C) and excellent cycling stability at 1 C over 300 cycles, giving rise to a capacity retention of 91.7% and an average capacity decline of 0.03% cycle(-1). (c) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.