Propelling polysulfide redox by Fe3C-FeN heterostructure@nitrogen-doped carbon framework towards high-efficiency Li-S batteries

Lithium-sulfur (Li-S) batteries hold great promise in next-generation high-energy-density energy storage systems, but the intractable shuttle effect and the sluggish redox kinetics of polysulfides hinder the practical implementation of Li-S batteries. Here, heterostructured Fe3C-FeN nanoparticles dotted in the three-dimensional-ordered nitrogen-doped carbon framework (Fe3C-FeN@NCF) were synthesized by molecular engineering combined with heterointerface engineering, and were applied to regulate the immobilization-diffusion-conversion behavior of polar polysulfides. It is experimentally and theoretically demonstrated that the heterointerface between Fe3C and FeN exhibits high sulfiphilicity and high electronic/ionic conductivity, thus effectively capturing polysulfides and accelerating the bidirectional conversion of sulfur species. Meanwhile, the holey carbon framework functions as the scaffold to highly disperse binary nanoparticles, ensuring the sufficient exposure of active sites and the easy accessibility for lithium ions and electrons. By virtue of these synergistic merits, the Li-S batteries based on Fe3C-FeN@NCF-modified separators afford excellent electrochemical performances including a high rate capacity of 858 mA h g(-1) at 2 C and a low capacity decay rate of 0.07% per cycle after 800 cycles at 1 C. This work provides inspiration for the design of heterostructured compounds and sheds light on the potential of heterostructure in high-efficiency Li-S batteries.(c) 2022 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.