Triple-Shell Hollow FeS/MoS₂ Heterostructure Anodes: Synergistic Effects of Built-In Electric Field on Ultra-Stable...

Metal sulfides are intensively pursed as promising anode materials for sodium-ion batteries (SIBs) owing to their high theoretical capacities, abundant and inexpensive raw materials, however, challenges remain in designing their structures, particularly due to the slow Na⁺ storage kinetics in individual sulfide, and unshaped and inefficient heterostructure persists the issue of low intrinsic ion conductivity. Herein, hollow triple-shell FeS/MoS₂@NC structure by integrating molecular and microstructural engineering is constructed. The intimate connection between FeS and MoS₂ in FeS/MoS₂@NC arises from the simultaneous sulfidation of Fe₂(MoO₄)₃. This hollow multi-shell structure, along with the high effective built-in electric field between the sulfides, effectively mitigates the volume expansion and propelled Na⁺ storage kinetics. Additionally, superparamagnetic Fe0 nanodots appeared from FeS reduction at low voltage during charge-discharge cycles facilitate Na+ storage. As a result, the hollow triple-shell FeS/MoS₂@NC presented high reversible capacity (611.8 mAh g^-1 at 0.1 A g^-1) and ultra-stable cycling span-life (451.5 mAh g^-1 after 9000 cycles at 5 A g-¹). In addition, the assembled Na₃V₂(PO₄)₃@rGO//FeS/MoS₂@NC coin-type full cell exhibited remarkable electrochemical performance (322.2 mAh g^-1 after 400 cycles at 1 A g^-1). This work will stimulate the further development of metal sulfide heterostructure and also provide new perspectives on high performance SIBs anodes.