High‐Temperature Stable and Long‐Life FeS @Hollow Carbon Composite as Anode Material for High‐Performance Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) are a promising alternative to lithium‐ion batteries due to their cost‐effectiveness and abundant sodium resources. However, their electrochemical performance is limited by the larger ionic radius and severe volume expansion of Na + ions. In this study, hollow yolk‐shell structured iron sulfide (FeS) was encapsulated in graphitized carbon (H‐C@FeS) to address these challenges. The material was synthesized using a solvothermal technique, followed by SiO 2 templating, carbon coating, and thermal treatment. The hollow structure buffered volume changes, while the carbon shell enhanced conductivity and structural stability. H‐C@FeS exhibited excellent electrochemical performance, delivering 450 and 350 mAhg −1 at 1.0 and 5.0 Ag −1 , respectively, with high‐capacity retention. Moreover, the electrode maintained stable capacities of 600 mAhg −1 at 60°C, indicating superior high‐temperature stability. Electrochemical analyses, including CV, GITT, and in situ EIS with DRT interpretation, confirmed enhanced Na + diffusion kinetics. The results suggest H‐C@FeS as a promising high‐performance and thermally stable anode for next‐generation SIBs.