Fe3O4 quantum dot decorated MoS2 nanosheet arrays on graphite paper as free-standing sodium-ion battery anodes

Abstract

A novel composite consisting of vertical ultrathin MoS₂ nanosheet arrays and Fe₃O₄ quantum dots (QDs) grown on graphite paper (GP) as a high-performance anode material for sodium-ion batteries (SIBs) has been synthesized via a facile two-step hydrothermal method. Owing to the high reversible capacity provided by the MoS₂ nanosheets and the superior high rate performance offered by Fe₃O₄ QDs, superior cycling and rate performances are achieved by Fe₃O₄@MoS₂-GP anodes during the subsequent electrochemical tests, delivering 468 and 231 mA h g⁻¹ at current densities of 100 and 3200 mA g⁻¹, respectively, as well as retaining ∼72.5% of their original capacitance at a current density of 100 mA g⁻¹ after 300 cycles. The excellent electrochemical performance resulted from the interconnected nanosheets of MoS₂ providing flexible substrates for the nanoparticle decoration and accommodating the volume changes of uniformly distributed Fe₃O₄ QDs during the cycling process. Moreover, Fe₃O₄ QDs primarily act as spacers to stabilize the composite structure, making the active surfaces of MoS₂ nanosheets accessible for electrolyte penetration during charge–discharge processes, which maximally utilized electrochemically active MoS₂ nanosheets and Fe₃O₄ QDs for sodium-ion batteries.