Bond-Defect Synergy Enabled Ultrastable and High-Rate Sodium Iron Phosphate Cathode through Zn/F Co Substitution.
basic_science · Level V
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- Record sourced from PubMed, PMID 41554633.
- Also identified by DOI 10.1021/acs.nanolett.5c05384.
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Abstract
Achieving both long-term stability and superior rate capability in Na<sub>4</sub>Fe<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>P<sub>2</sub>O<sub>7</sub> (NFPP) cathodes remains a major challenge for sodium-ion batteries. Herein, we demonstrate a synergistic bond-defect strategy that circumvents this trade-off. The complementary interaction between Zn and F establishes a synergistic bond-defect environment. The strong bonding of Zn<sup>2+</sup> mitigates the charge localization associated with F<sup>-</sup> doping. Furthermore, the strategy narrows the electronic bandgap to near-metallic values and enhances the degree of graphitization in carbon coatings, resulting in a marked improvement in electronic conductivity. The optimized Na<sub>3.95</sub>Fe<sub>2.95</sub>Zn<sub>0.05</sub>(PO<sub>4</sub>)<sub>2</sub>P<sub>2</sub>O<sub>6.95</sub>F<sub>0.05</sub> (NFZPPF) exhibits outstanding cycling stability with 76.25% retention after 16,000 cycles at 20 C and remarkable rate performance, delivering 68.6 mAh g<sup>-1</sup> at 50 C. Coupled with a hard carbon anode, the full cell retains 88.8% capacity after 200 cycles at 2 C, underscoring its viability for practical sodium-ion storage.