Phosphorus-doped few-layer graphite wrapped metallic cobalt as interlayer for advanced lithium–sulfur batteries

Abstract

The shuttle effect and sluggish redox kinetics of sulfur cathode are the main barriers to commercializing lithium-sulfur (Li–S) batteries. Fabricating functional interlayers is considered as one of the efficient approaches to suppress the shuttle effect while accelerating the conversion kinetics of polysulfides. Herein, the nanofiber-type interlayer composed of cobalt wrapped with few-layer phosphorus-doped graphite (CoPG) is elaborately designed, which is expected to chemically adsorb the polysulfides while accelerating the redox conversion of polysulfides anchored on phosphorus-doped graphite. Electrochemical measurements sufficiently verify that the usage of the designed CoPG interlayer significantly prolongs the longevity of Li–S batteries, reaching 694 mAh/g with a capacity decay rate of 0.11% at the current density of 2.0C. Remarkably, Li–S battery sustains for 125 cycles and maintains ultrahigh capacity retention of 92% at the current density of 0.2C even with a sulfur loading of 5.8 mg/cm2. The theoretical computation further confirms the intensive interactions between CoPG and polysulfides, consistent with the experimental outcomes. Encapsulating the electrocatalyst with a few-layer polarized graphite enables the interlayer with adsorption and catalysis functions, which provides a promising strategy for advanced Li–S batteries.