writer：Chunliu Xu, Yongchun Li, Guilin Feng, Zhao Chen, Xiaowei Li, Zhenguo Wu, Weiqing Yang, Xiaodong Guo, Junmei Zhao, Yong-Sheng Hu
keywords：NASICON-type cathode，polyanionic cathodes，sodium-ion batteries，iron-based cathodes，induced effects，Na+ diffusion kinetics，energy density，operating voltage
source：期刊
Issue time：2026年

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 Fe 2+ /Fe 3+ redox potential, which is intrinsically dependent on the chemical coordination nature of the polyanion groups. Herein, the induced effects are carefully regulated by SO 4 /PO 4 polyanions substitution engineering to maintain favorable kinetics and elevate Fe 2+ /Fe 3+ redox potential. The reduced Fe-O covalency can enlarge energy gap between antibonding orbital and Fermi energy level, finally increasing the potential of Fe 2+ /Fe 3+ redox couples. As concept proof, NASICON-type Na 0.6 Fe 2 (PO 4 ) 0.6 (SO 4 ) 2.4 with suitable SO 4 /PO 4 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 NaFe 2 (PO 4 )(SO 4 ) 2 and ~2.45 V of Na 3 Fe 2 (PO 4 ) 3 ), achieving 400 W h kg -1 -level energy density