PPy‐Derived Sandwich‐Structured Hollow Carbon Fiber Anchoring Sn₄P₃ as Anode Materials with Improved Na⁺ Storage

Abstract Sn₄P₃ has been considered as one of the promising anode materials for sodium ion batteries (SIBs) due to its high reversible capacity and low redox potential. However, the large volume expansion and Sn aggregation during the sodiation‐desodiation process result in the poor cycle stability, limiting its commercial use. Herein, a sandwich‐structured hollow carbon fiber anchoring Sn₄P₃ quantum dots (C@Sn₄P₃@HCF) is synthesized by carbon coating, carbonization/reduction and phosphorization with PPy hollow fiber as a template. Benefitting from the unique sandwiched architecture as well as the synergistic effect between Sn₄P₃ and N‐doped hollow carbon fiber, C@Sn₄P₃@HCF hybrids deliver a high initial discharge capacity of 631 mAh g⁻¹ at 100 mA g⁻¹, excellent rate capability (205 mAh g⁻¹ at 50 mA g⁻¹, 108 mAh g⁻¹ at 1500 mA g⁻¹) and ultrastable capacity retention of >103 mAh g⁻¹ with a coulombic efficiency of 99.4% over 1000 cycles at 300 mA g⁻¹. Hence, C@Sn₄P₃@HCF hybrids show great potential as an alternative anode material for next‐generation SIBs.