Integrating Conductivity, Immobility, and Catalytic Ability into High-N Carbon/Graphene Sheets as an Effective Sulfur Host.

Abstract

Lithium-sulfur (Li-S) batteries are considered to be one of the most promising candidate systems for next-generation electrochemical energy storage. The major challenge of this system is the polysulfide shuttle, which results in poor cycling efficiency. In this work, a highly N-doped carbon/graphene (NC/G) sheet is designed as a sulfur host, which combines the merits of abundant N active sites and high electrical conductivity to achieve in situ anchoring-conversion of lithium polysulfides (LiPSs). Such a host not only has strong binding with LiPSs but also promotes redox kinetics, which are revealed by both experimental investigations and theoretical studies. The sulfur cathode based on the NC/G host exhibits a high initial capacity of 1380 mA h g^-1 and a superior cycle stability with a low capacity decay of 0.037% per cycle within 500 cycles at 2 C. Steady areal capacity with a high sulfur loading (5.6 mg cm^-2 ) is also attained even without the addition of LiNO₃ in the electrolyte. This work proposes and illustrates the importance of in situ anchoring-conversion of LiPSs, offering a new strategy to design multifunctional sulfur hosts for high-performance Li-S batteries.