Ultrathin MoS2 nanosheets homogenously embedded in a N,O-codoped carbon matrix for high-performance lithium and sodium storage

Abstract

MoS₂ nanosheets, which possess a high theoretical capacity, have drawn wide attention as an anode material for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). However, MoS₂ nanosheets suffer from poor cycling stability and rate performance caused by structural deterioration, large volume change upon cycling, poor conductivity, and aggregation of nanosheets. Here, a MoS₂/C nanocomposite with ultrathin MoS₂ nanosheets homogenously embedded in a N,O-codoped carbon matrix is obtained under high pressure by pyrolysis of a solution of ammonium tetrathiomolybdate dissolved in dimethylformamide in a sealed vessel. The MoS₂/C nanocomposite possesses a unique structure with an expanded interlayer spacing of 10.5 Å for the MoS₂ nanosheets and formation of Mo–O–C and Mo–N–C bonds at the interface between the MoS₂ nanosheets and carbon matrix. The expansion of the interlayer spacing for the MoS₂ nanosheets may result from insertion of single-layer carbon atoms in between MoS₂ layers. The unique structure is beneficial for solving the above-mentioned problems and thus obtaining superior lithium and sodium storage performances. As an anode for LIBs, MoS₂/C delivers excellent cyclability (capacity retention of 115.4% after 2700 cycles) and superior rate capability (234.7 mA h g⁻¹ at 20C). As an anode for SIBs, MoS₂/C exhibits excellent cycling performance (capacity retention of 91.5% after 100 cycles) and outstanding rate performance (187.9 mA h g⁻¹ at 5C).