High‐Entropy Engineering of 1D Na ₄ Fe ₃ (PO ₄ ) ₂ P ₂ O ₇ : Unlocking Exceptional Capacity and Ultrahigh Rate Capability for Sodium‐Ion Battery Cathodes

Na₄Fe₃(PO₄)₂P₂O₇ is thought to be a promising cathode material for sodium-ion batteries (SIBs) because of its inexpensive cost and quick 3D pathways for sodium ion migration. However, traditional modified methods often result in the formation of electrochemically inactive triphylite NaFePO₄ and low-capacity NaFeP₂O₇, alongside low electronic conductivity, leading to a capacity loss for Na₄Fe₃(PO₄)₂P₂O₇. Herein, this investigation presents the initial development of an innovative 1D, high-entropy Na₄Fe_2.5(MgCuZnNiCo)_0.1(PO₄)₂P₂O₇ (NFPP-HEES) cathode material tailored for SIBs, utilizing electrostatic spinning technology for the first instance, which exhibits incredible reversible capacity and ultrahigh rate performance. The electrochemical activity of Ni²⁺ contributes to the maintenance of high specific capacity in NFPP-HEES, reaching 127.6 mAh g^-1. Additionally, Zn, Co, Cu, and Mg serve as structural pillars, minimizing the cell volume change of NFPP-HEES to a remarkable 0.02%. This results in improved rate performance and cycling stability, especially at 50 C, where the capacity remains at 90 mAh g^-1. The synergetic effect of high-entropy ions significantly narrows the bandgap of NFPP-HEES and diminishes the Na⁺ diffusion energy barrier, thereby substantially improving the kinetic performance. This research presents a novel strategy for the advancement of SIBs cathode materials with high capacity and superior rate capability.