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<p>Iron-based NASICON-type polyanion materials are regarded as one of the most promising cathodes because of their low cost, three-dimensional Na<sup>+</sup> ion diffusion and robust structure stability for Na-ion batteries. However, the energy density of NASICON-type polyanion cathodes is greatly restricted by low Fe<sup>2+</sup>/Fe<sup>3+</sup> redox potential, which is intrinsically dependent on the chemical coordination nature of the polyanion groups. Herein, the induced effects are carefully regulated by SO<sub>4</sub>/PO<sub>4</sub> polyanions substitution engineering to maintain favorable kinetics and elevate Fe<sup>2+</sup>/Fe<sup>3+</sup> redox potential. The reduced Fe-O covalency can enlarge energy gap between antibonding orbital and Fermi energy level, finally increasing the potential of Fe<sup>2+</sup>/Fe<sup>3+</sup> redox couples. As concept proof, NASICON-type Na<sub>0.6</sub>Fe<sub>2</sub>(PO<sub>4</sub>)<sub>0.6</sub>(SO<sub>4</sub>)<sub>2.4</sub> with suitable SO<sub>4</sub>/PO<sub>4</sub> polyanion groups ratio delivers the enhanced induced effects with facilitated Na<sup>+</sup> migration kinetics, which enables an increased average working voltage of ~3.2 V (<i>vs</i>. ~ 2.8 V of NaFe<sub>2</sub>(PO<sub>4</sub>)(SO<sub>4</sub>)<sub>2</sub> and ~2.45 V of Na<sub>3</sub>Fe<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>), achieving 400 W h kg<sup>-1</sup>-level energy density.</p>

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Induced effect regulation of Nasicon-Type polyanion cathodes toward high-energy Na-ion batteries

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月3日

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  • Chunliu Xu,
  • Yongchun Li,
  • Guilin Feng,
  • Zhao Chen,
  • Xiaowei Li,
  • Zhenguo Wu,
  • Weiqing Yang,
  • Xiaodong Guo,
  • Junmei Zhao,
  • Yong-Sheng Hu

摘要

Iron-based NASICON-type polyanion materials are regarded as one of the most promising cathodes because of their low cost, three-dimensional Na+ ion diffusion and robust structure stability for Na-ion batteries. However, the energy density of NASICON-type polyanion cathodes is greatly restricted by low Fe2+/Fe3+ redox potential, which is intrinsically dependent on the chemical coordination nature of the polyanion groups. Herein, the induced effects are carefully regulated by SO4/PO4 polyanions substitution engineering to maintain favorable kinetics and elevate Fe2+/Fe3+ redox potential. The reduced Fe-O covalency can enlarge energy gap between antibonding orbital and Fermi energy level, finally increasing the potential of Fe2+/Fe3+ redox couples. As concept proof, NASICON-type Na0.6Fe2(PO4)0.6(SO4)2.4 with suitable SO4/PO4 polyanion groups ratio delivers the enhanced induced effects with facilitated Na+ migration kinetics, which enables an increased average working voltage of ~3.2 V (vs. ~ 2.8 V of NaFe2(PO4)(SO4)2 and ~2.45 V of Na3Fe2(PO4)3), achieving 400 W h kg-1-level energy density.