Carbon-Based Cathode Design for Next-Generation Potassium-Sulfur Batteries: Status and Perspective

The increasing concern for environmental pollution has fastened the development of energy storage devices. Among various devices, lithium-ion battery (LIB) technology has been leapfrogged owing to its stable performance for various applications ranging from electronic gadgets to electric vehicles (EVs). For ever-increasing number of EVs has increased the demand for batteries increasing the overall cost. An alternative energy storage device that can replace the dependence on lithium reserves can be another game changer in this area. Potassium-sulfur batteries (KSBs) have attracted enormous attention owing to the higher abundance of sulfur and potassium. In addition, sulfur bears the highest capacity as a cathodic material (nearly five times higher than the commercial LIBs) and when clubbed with potassium anode can deliver a theoretical energy density of 914 Wh/kg (significantly higher for EVs). However, KSB development is still in the nascent stage owing to the intrinsic challenges including insulating sulfur, volume variation, and shuttle effect of polysulfides. In addition, unstable potassium anode and its dendrite formation is another thorny problem for KSB. The use of carbon matrices for cathode fabrication has been proven to be an excellent choice by initial research on KSB and experience with other metal-sulfur batteries. This can be related to the higher electronic conductivity of carbon, easy tunability, high specific surface area, and porous morphology. This review is an attempt to show the usage of carbon as a sulfur host for KSBs and its performance. Further, we shed light on flexible and binder-free carbon electrodes for the development of KSBs, which can be adopted to develop flexible batteries to be used in wearable devices. Finally, we present our perspective for developing a high-performance carbon-based cathode material for developing a reliable and long-cycle life KSB.