Enhancing Polysulfide Confinement and Redox Kinetics by Electrocatalytic Interlayer for Highly Stable Lithium-Sulfur Batteries

Enhancing active material utilization and restricting lithium polysulfide (LPS) shuttle effect are the bottlenecks for developing stable and high-performance Lithium-Sulfur (Li-S) batteries. Herein, we present the in-situ nitrogen-doped bamboo/compartmental structured carbon nanotubes (BNT) without and with iron carbide nanoparticle encapsulation (Fe3C/BNT) as the sulfur host and electrocatalytic interlayer for Li-S batteries. The compartmental/bamboo structured BNT has a high specific surface area which helps in facilitating the transport of electrons/Li+ ions and also provides the interspace for sulfur volume expansion during the sulfur redox reactions. The symmetric cell studies show that the presence of Fe3C in BNT accelerates LPS redox reactions for the formation of Li2S and vice-versa. The synergistic combination of BNT-S cathode with Fe3C/BNT interlayer delivers a specific capacity of 1235 mA h g(-1) at 0.1C-rate and cyclic stability for 500 cycles with 0.032% capacity fading rate, suggesting the strong chemical interaction and electrocatalytic activity of Fe3C/BNT towards intermediate LPS. The present study also investigates the superior catalytic activity of Fe3C/BNT interlayer and the interfacial sulfur redox kinetics during the charge and discharge processes by dynamic electrochemical impedance spectroscopy. Therefore, this study demonstrates a new and efficient strategy for developing high-performance Li-S batteries by using low-cost cathode materials towards the catalytic conversion of lithium polysulfides. (C) 2020 Elsevier Ltd. All rights reserved.