Triple‐Shell Hollow FeS/MoS 2 Heterostructure Anodes: Synergistic Effects of Built‐In Electric Field on Ultra‐Stable Sodium Storage

Abstract 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/MoS 2 @NC structure by integrating molecular and microstructural engineering is constructed. The intimate connection between FeS and MoS 2 in FeS/MoS 2 @NC arises from the simultaneous sulfidation of Fe 2 (MoO 4 ) 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/MoS 2 @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 Na 3 V 2 (PO 4 ) 3 @rGO//FeS/MoS 2 @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.