Covalent S and Cl grafted porous carbon host realized via the one-step pyrolysis method results in boosted Li–O2 battery performances

Abstract

Li–O2 battery has attracted wide attention because it can satisfy the need for a new energy storage system with high energy density. However, poor oxygen reduction (ORR)/oxygen evolution (OER) kinetics involving Li2O2 formation/decomposition is a major obstacle to its development. By designing suitable cathode with desired structure and surface electronic states, the formation/morphology of Li2O2 and the reaction kinetics of charge process can be efficiently optimized simultaneously. In this work, a novel sulfur (S) and chlorine (Cl) co-doped porous carbon (CSC) were synthesized by one-step pyrolysis strategy, and the amount of heterogeneous atoms could be flexibly controlled by different calcination temperatures. Experimental combined with theoretical calculations show that the content of CCl bond plays an important role in the adsorption of intermediate LiO2, thus regulating the morphology of Li2O2 and ultimately affecting the release of battery energy. The CS bond mainly acts on the dynamics of the ORR and OER processes, which has an important influence on improving the round-trip efficiency of the battery. Benefiting from the synergistic effect of heteroatoms, the electrochemical performances of the Li–O2 battery, including round-trip efficiency, discharge capacity and cycling stability are greatly improved.