Up-Scalable Conversion of White-Waste Polystyrene Foams to Sulfur, Phosphorus-Codoped Porous Carbon for High-Performance Lithium–Sulfur Batteries

Abstract

Discarded polystyrene foams as white wastes, at least two million tons in demand annually in China, are threatening environment and health because of their formidable degradation, which increase in quantity with a reported rate of about 15% per year. Here, we employ a facile and up-scalable approach to convert discarded polystyrene foams to S,P-codoped porous carbon (SPPC) as the effective sulfur mobilizer for lithium–sulfur batteries. The high porosity of SPPC can ensure high loading of sulfur with effective physical adsorption to polysulfides, and the heteroatom codoping of sulfur and phosphorus can enhance the electrical conductivity of carbon effectively with strong chemical immobilization for polysulfides. These effects are together responsible for the superior performance of S@SPPC with a sulfur loading of 72 wt %. The S@SPPC cathode with an areal sulfur loading of 2 mg cm–2 exhibits an initial capacity of 893 mA h g–1 at 2 C with only a small capacity loss of 0.049% per cycle over 800 cycles. The cathode still exhibits both superior rate capability, and stable cycling performance for a capacity decay rate of 0.06% per cycle over 600 cycles at 2 C by increasing the areal sulfur loading to 4.8 mg cm–2 and a capacity of 694 mA h g–1 retained after 150 cycles for 0.5 C at a much reduced electrolyte-to-sulfur ratio of 5 mL g–1. This study offers a route for realizing the up-scalable conversion of “waste” to “treasure,” which is significant for practical applications in energy storage.