Amino-functionalized reduced graphene oxide@MoS2@CoS2 heterostructure as a high-rate anode material for ultralong lifespan sodium–sulfur batteries

Abstract

A nanocomposite comprising MoS₂@CoS₂ amino-functionalized graphene (En-RGO) with a two-dimensional structure has been successfully synthesized using a simple self-assembly technique. The resulting cell with a MoS₂@CoS₂@En-RGO anode and a sulfur cathode exhibits a superior hierarchical architecture that significantly facilitates ion mobility, cell conductivity, and pseudocapacitance. Consequently, this leads to improved rate performance and extended cycle stability in Na–S batteries. Micron-sized CoS₂ was synthesized by solvothermal growth of MoS₂ nanosheets on its surface. This composite material presents enhanced sodium-ion diffusion kinetics attributed to its heterogeneous interface, reduced ion diffusion pathways and increased exposure of active sites for sodium storage due to its hierarchical nanosheet structure. Additionally, amino functionalized graphene oxide with uniform nitrogen doping could improve electronic conductivity. The cell employing MoS₂@CoS₂@En-RGO with superior ion mobility and enhanced adsorption energy of Na⁺ ions achieves a cycle stability of 541.2 mA h g⁻¹ after 1800 cycles. The increased adsorption energy facilitates a more efficient sodiation process at MoS₂@CoS₂@En-RGO compared to En-RGO. Additionally, the MoS₂@CoS₂@En-RGO anode demonstrates a capacity retention of 95.8% after 1800 cycles at 1 A g⁻¹. The enhanced mobility of Na ions and the effective adsorption of polysulfide chains in MoS₂@CoS₂@En-RGO have been examined through DFT calculations, confirming its potential as a promising anode material for the advancement of high-performance Na–S batteries.