Fe1−xS@S-doped carbon core–shell heterostructured hollow spheres as highly reversible anode materials for sodium ion batteries

Abstract

Iron sulfide (Fe_1−xS) has been considered as a promising anode material for sodium ion batteries (SIBs) because of its high theoretical capacity. However, Fe_1−xS suffers from large volume change and sulfur dissolution issues during the sodiation/desodiation process, which lead to a poor cycle performance. Here, heterostructured Fe_1−xS@S-doped carbon (Fe_1−xS@SC) hollow spheres (HSs) have been prepared as SIB anode material. The Fe_1−xS@SC HSs show a high reversible capacity of 776.2 mA h g⁻¹ at 0.2 A g⁻¹ and 454.3 mA h g⁻¹ at 1.0 A g⁻¹ after 500 cycles. The constructed Fe_1−xS/SC heterojunctions play a key role in alleviating the large volume variation and stabilizing the reaction products Fe⁰ and Na₂S, thus enhancing the conversion reaction kinetics of Fe⁰ and Na₂S and ultimately resulting in a highly reversible conversion reaction. This work provides a possibility to solve the reversibility issue of conversion-type anode materials.