Tuning the structure and composition of graphite-phase polymeric carbon nitride/reduced graphene oxide composites towards enhanced lithium-sulfur batteries performance

摘要

Lithium-sulfur (Li-S) batteries have been attractive alternatives to lithium-ion (Li-ion) batteries due to the high theoretical capacity of sulfur cathode. However, the polysulfide shuttling effect is detrimental to the long-term cycling stability. Chemically absorptive host materials provide an effective way to mitigate the dissolution of lithium polysulfide. Carbon nitride (C3N4) is one of the effective host materials with strong interaction with polysulfide species. The low electronic conductivity, however, is unfavorable for high sulfur utilization. In this work, we report the controlled synthesis of porous, well-interconnected C3N4/reduced graphene oxide (rGO) aerogels as hybrid sulfur host using a simple hydrothermal reaction followed by freeze-drying, which combines the structural merits of both highly conductive rGO networks and chemically active C3N4. By further tuning the structure/morphology and the ratio between C3N4 and rGO, we have demonstrated the C3N4/rGO composites with optimized 1: 2 ratio of C3N4: rGO (termed as CG12) exhibits not only very high sulfur utilization but also excellent rate capability compared to other C3N4/rGO composites, pure rGO, and C3N4. The compositionally and structurally tailored CG12 also shows stable cycling performance over 400 cycles with a low decay rate of 0.09% per cycle. (C) 2017 Elsevier Ltd. All rights reserved.