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).