Abstract
Iron-ion batteries represent a compelling energy storage solution due to the cost-effectiveness, suitable redox potential, and high capacity of Fe negative electrodes. Polyaniline positive electrodes for iron-ion batteries have demonstrated promising electrochemical redox properties, but face limited redox-accessible groups and unstable −NH− sites. Here we show phosphorus redox activity in a carboxyl small molecule electrode. 4,4′,4″-phosphanetriyltribenzoic acid and 4,4′,4″-nitrilotribenzoic acid are designed via modulating the electron-donating P and tert-N motifs, showing tuned charge distributions and energy levels. With the decrease of the electronegativity and energy barrier (N > P), 4,4′,4″-phosphanetriyltribenzoic acid exhibits stronger Fe2+ coordination with carboxyl sites, and brings closed CF3SO3− proximity to P centers. This feature ensures high activity of carboxyl/phosphorus sites with low activation energy (0.24 vs. 0.29 eV for 4,4′,4″-nitrilotribenzoic acid). 4,4′,4″-phosphanetriyltribenzoic acid with P-extended conjugated structure achieves low energy gap (2.28 eV) compared to its individual carboxyl or P-containing counterparts (2.71/3.16 eV), thereby enabling high utilization of carboxyl/P motifs (98.5%) and enhanced redox voltage (0.8 V). A stable 4 e− Fe2+/CF3SO3− storage of 4,4′,4″-phosphanetriyltribenzoic acid positive electrode endows Fe battery with high specific capacity (276 mAh g−1) and cycling stability (60,000 cycles). This work highlights the potential of phosphorus-active organic materials toward iron-ion batteries.
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Acknowledgments
This work is financially supported by the National Natural Science Foundation of China (NO. 22272118, M.L.; NO. 22172111, L.G.; NO. 22309134, Z.S. and NO. 22502144, Y.Z.), the Shanghai Rising-Star Program (23YF1449200, Z.S.), the Postdoctoral Fellowship Program of CPSF (GZC20250749, Y.Z.), the Zhejiang Provincial Science and Technology Project (NO. 2022C01182, Y.L.), and the Fundamental Research Funds for the Central Universities (Z.S.).
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Y.Z. conceived the idea and designed the project. M.L. supervised the experiments and edited the paper. Z.S., L.G., Y.L., and P.L. performed the data processing and analysis. Q.H. performed a computational simulation. Y.Z., Z.S., and M.L. contributed to the manuscript review. All authors discussed the results and contributed to the completion of the manuscript.
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Zhang, Y., Huang, Q., Liu, P. et al. Phosphorus-activated carboxyl small molecule positive electrode for high specific capacity and long-life iron-organic batteries. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70800-w
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DOI: https://doi.org/10.1038/s41467-026-70800-w
