Phosphorus-doped graphene nanosheets anchored with cerium oxide nanocrystals as effective sulfur hosts for high performance lithium-sulfur batteries.

Abstract

To meet the ever-increasing market requirements for energy storage devices with improved performances, lithium-sulfur (Li-S) batteries with high theoretical capacity and energy density have been extensively studied. However, to bring Li-S batteries into real life, several challenges still need to be overcome, such as dissolution of intermediate polysulfides, large volume change, and low electrical conductivity of sulfur. In this study, phosphorus-doped graphene anchored with well-dispersed cerium oxide nanocrystals (CeO2/PG) were prepared as effective sulfur host materials through a hydrothermal synthesis method followed by a thermal treatment process. The cerium oxide nanocrystals/phosphorus-doped graphene (CeO2/PG) nanocomposites can provide high electrical conductivity, sufficient spaces for the storage of sulfur, and strong chemical binding with polysulfides. In particular, well-dispersed polar CeO2 nanocrystals effectively exhibit chemical affinity with polysulfides and promote polysulfide redox reactions during the cycling. Furthermore, phosphorus dopants can offer a sufficient number of active sites for polysulfide trapping and enhance the overall electrical conductivity of graphene nanosheets. As a result, a S@CeO2/PG cathode with 72.3 wt% sulfur content exhibits a high specific capacity (1287 mA h g-1 at 0.1 C-rate) and good cycling stability (577.7 mA h g-1 at 1 C-rate after 100 cycles).