PEG400-assisted synthesis of oxygen-incorporated MoS2 ultrathin nanosheets supported on reduced graphene oxide for sodium ion batteries

Highlights: • PEG400 promotes the formation of single-phase oxygen-incorporated MoS₂. • Oxygen-incorporation improves the intrinsic electronic conductivity of MoS₂. • The rGO can regulate the oxygen content and produce confinement effect. • OI-MoS₂/L-rGO composite exhibits excellent electrochemical performance. Oxygen-incorporated MoS₂ (OI-MoS₂) ultrathin nanosheets have been successfully fabricated using a PEG400-assisted one-pot hydrothermal method. The role of polyethylene-glycol 400 (PEG400) in promoting the formation of long-range ordered single-phase OI-MoS₂ has not been investigated previously. In our study, we demonstrate that polyethylene-glycol 400 (PEG400) can act as a surfactant to reduce nanosheet aggregation. Furthermore, it can function as a structural modifier to regulate the degree of sulfidation and stabilize the oxygen-incorporated structure with larger interlayer spacing and higher intrinsic electronic conductivity for facilitating sodiation/de-sodiation reactions. A very low content of reduced graphene oxide (rGO) is enough to provide a highway for electron transport between adjacent OI-MoS₂ layers, and prevent OI-MoS₂ layers from stacking in the [002] direction. Enhanced electrochemical performance is observed in the OI-MoS₂/L-rGO nanosheets with carbonate-based electrolyte, delivering a discharge capacity of 462 mAh g⁻¹ during the 2nd cycle with 89.1% capacity retention after 50 cycles.