Coupling Fe3O4/Fe1-xS@Carbon with carbon-coated MoS2 nanosheets as a superior anode for sodium-ion batteries

Abstract

Considering the natural reserves, distribution and cost of sodium resources, sodium-ion batteries (SIBs) have been regarded as a potential alternative to lithium-ion batteries. However, it remains challenging to develop the excellent electrode materials for SIBs owing to larger Na ionic radius. Herein, multicomponent Fe3O4/Fe1-xS@C@MoS2@C hybrid has been designed by using bone-like Fe3O4@C particles and carbon-coated MoS2 nanosheets as the core and shell, respectively, followed by sulfurization. On one hand, several high-capacity active materials are well organized together, which can fully exert the synergies among them. Meanwhile, ultrathin MoS2 nanosheets with expanded interlayer spacing of 0.80 nm are confined between two carbon layers, resulting in the high conductivity and good structural stability of the whole electrode. Consequently, the prepared Fe3O4/Fe1-xS@C@MoS2@C anode for SIBs exhibits a large reversible capacity of 589.8 mA h/g at 100 mA/g after 200 cycles. Even at a higher current density of 2 A/g, it still keeps a high specific capacity of 503.7 mA h/g. The theoretical calculations further show that the surface of Fe1-xS is more advantageous for Na+ adsorption in comparison to that of Fe3O4, due to the stronger charge transfer between Na and neighboring S atoms, which greatly boosts the sodium storage capability of Fe3O4/Fe1-xS@C@MoS2@C.