A New Graphitic Nitride and Reduced Graphene Oxide-Based Sulfur Cathode for High-Capacity Lithium-Sulfur Cells

Abstract

Lithium-sulfur (Li-S) batteries can provide at least three times higher energy density than lithium-ion (Li-Ion) batteries. However, Li-S batteries suffer from a phenomenon called the polysulfide shuttle (PSS) that prevents the commercialization of these batteries. The PSS has several undesirable effects, such as depletion of active materials from the cathode, deleterious reactions between the lithium anode and electrolyte soluble lithium polysulfides, resulting in unfavorable coulombic efficiency, and poor cycle life of the battery. In this study, a new sulfur cathode composed of graphitic nitride as the polysulfide absorbing material and reduced graphene oxide as the conductive carbon host has been synthesized to rectify the problems associated with the PSS effect. This composite cathode design effectively retains lithium polysulfide intermediates within the cathode structure. The S@RGO/GN cathode displayed excellent capacity retention compared to similar RGO-based sulfur cathodes published by other groups by delivering an initial specific capacity of 1415 mA h g⁻¹ at 0.2 C. In addition, the long-term cycling stability was outstanding (capacity decay at the rate of only 0.2% per cycle after 150 cycles).