Phosphorus-catalyzed graphitization strategy toward superior Na-storage performance of Na₄Fe₃(PO₄)₂P₂O₇/C cathodes

Abstract

The Na₄Fe₃(PO₄)₂P₂O₇/C composite (NFPP-E) featuring a highly graphitized N- and P-co-doped carbon coating and hierarchical pore structure was successfully synthesized using a facile ball-milling-calcination approach. Ethylenediamine tetra(methylene phosphonic acid) (EDTMPA) acts as a multifunctional precursor and concurrently serves as a chelating, phosphorus, carbon, nitrogen, and pore-forming agent. The unique “phosphorus-catalyzed graphitization” effect during EDTMPA pyrolysis plays a pivotal role; the released active phosphorus oxides facilitate the ordered transformation of the carbon matrix, thereby yielding a highly graphitized N- and P-co-doped carbon coating with a low defect density. Electrochemical measurements demonstrated significant performance enhancements of NFPP-E relative to the sample prepared with conventional NH₄H₂PO₄. Specifically, NFPP-E delivered a high reversible capacity of 103.09 mAh·g⁻¹ at 0.1 C (1 C = 129 mA·g⁻¹) and retained 77.41 mAh·g⁻¹ even at an elevated rate of 10 C, demonstrating excellent rate capability. Furthermore, it exhibited superior long-term cycling stability, with a capacity retention rate of 94.9% after 500 cycles at 1 C. When assembled into a full cell with hard carbon as the anode, the NFPP-E achieved a capacity retention rate of 92.74% over 200 cycles, highlighting its great potential for practical applications. This study not only uncovers the universal principle for regulating the structure and properties of carbon layers via the “phosphorus-catalyzed graphitization” mechanism using organic phosphonic acid precursors but also offers a novel strategy for the development of high-performance and low-cost cathode materials for sodium-ion batteries.

Keywords

sodium-ion batteries / cathode / Na₄Fe₃(PO₄)₂P₂O₇ / EDTMPA / phosphorus-catalyzed graphitization

References

[1] Z.C. Zhu, D.D. Qiao, Y.F. Huang, J.J. Zhu, Y.J. Zheng, and Q.W. Chen, Comparative study of performance and hybrid battery configuration of sodium-ion and lithium-ion batteries, J. Energy Storage, 140(2025), art. No. 118904.

[2] Ellis BL, Nazar LF. Sodium and sodium-ion energy storage batteries. Curr. Opin. Solid State Mater. Sci., 2012, 16(4): 168

[3] Hwang JY, Myung ST, Sun YK. Sodium-ion batteries: Present and future. Chem. Soc. Rev., 2017, 46(12): 3529

[4] Kim SW, Seo DH, Xiaohua M, Ceder G, Kang K. Electrode materials for rechargeable sodium-ion batteries: Potential alternatives to current lithium-ion batteries. Adv. Energy Mater., 2012, 2(7): 710

[5] Kubota K, Komaba S. Review: Practical issues and future perspective for Na-ion batteries. J. Electrochem. Soc., 2015, 162(14): A2538

[6] Kundu D, Talaie E, Duffort V, Nazar LF. The emerging chemistry of sodium ion batteries for electrochemical energy storage. Angew. Chem. Int. Ed., 2015, 54(11): 3431

[7] H.L. Pan, Y.S. Hu, and L.Q. Chen, Room-temperature stationary sodium-ion batteries for large-scale electric energy storage, Energy Environ. Sci., 6(2013), No. 8, art. No. 2338.

[8] Yabuuchi N, Kubota K, Dahbi M, Komaba S. Research development on sodium-ion batteries. Chem. Rev., 2014, 114(23): 11636

[9] Slater MD, Kim D, Lee E, Johnson CS. Sodium-ion batteries. Adv. Funct. Mater., 2013, 23(8): 947

[10] Ren QC, Pei Y, Xiang YX, et al.. Out-of-plane symmetry design arrests structural evolution in layered-type framework for sustainable sodium shuttling. J. Am. Chem. Soc., 2026, 148(10): 10356

[11] C. Liu, Z. Zhang, H.Y. Liao, et al., Unlocking the potential: Na₄Fe₃(PO₄)₂(P₂O₇) supporting the innovation of commercial sodium-ion batteries, Adv. Funct. Mater., 35(2025), No. 23, art. No. 2424759.

[12] Z. Ahsan, Z.F. Cai, S. Wang, et al., Recent development of phosphate based polyanion cathode materials for sodium-ion batteries, Adv. Energy Mater., 14(2024), No. 27, art. No. 2400373.

[13] X.Y. Lu, S.Q. Li, Y. Li, F. Wu, C. Wu, and Y. Bai, From lab to application: Challenges and opportunities in achieving fast charging with polyanionic cathodes for sodium-ion batteries, Adv. Mater., 36(2024), No. 36, art. No. 2407359.

[14] S. Ryu, J.E. Wang, J.H. Kim, R. Ruffo, Y.H. Jung, and D.K. Kim, A study on cobalt substitution in sodium manganese mixed-anion phosphates as positive electrode materials for Na-ion batteries, J. Power Sources, 444(2019), art. No. 227274.

[15] Wu XH, Zhong GM, Yang Y. Sol–gel synthesis of Na₄Fe₃(PO₄)₂(P₂O₇)/C nanocomposite for sodium ion batteries and new insights into microstructural evolution during sodium extraction. J. Power Sources, 2016, 327: 666

[16] X.R. Qi, H.H. Dong, H. Yan, et al., Hollow core-shelled Na₄Fe_2.4Ni_0.6(PO₄)₂P₂O₇ with tiny-void space capable fast-charge and low-temperature sodium storage, Angew. Chem. Int. Ed., 63(2024), No. 40, art. No. e202410590.

[17] X.T. Zhang, X.X. Yin, J. Xie, et al., Lanthanum-doped Na₄Fe₃(PO₄)₂P₂O₇/C as cathode materials in sodium-ion batteries: Enhanced ion diffusion kinetics and embedded pseudocapacitance, J. Power Sources, 635(2025), art. No. 236531.

[18] Che JL, Yu JJ, Xu T, et al.. Sodium storage properties of Fe, Ni-bimetallic doped carbon-modified NaTi₂(PO₄)₃. Int. J. Miner. Metall. Mater., 2025, 32(9): 2249

[19] Yu ZD, Liu XJ, Liu ZC, et al.. Understanding of TiO₂/Co₃O₄-modified configuration strategy for stabilizing O3-type NaNi_0.4Fe_0.2Mn_0.4O₂ cathodes with enhanced long-term and rate performance. Int. J. Miner. Metall. Mater., 2025, 32(11): 2806

[20] F. Peng, P.Y. Dong, C.D. Chen, et al., Spherical Mg/Cu co-doped Na₄Fe₃(PO₄)₂P₂O₇ cathode materials with mitigated diffusion-induced stresses and enhanced cyclic stability, Angew. Chem. Int. Ed., 64(2025), No. 12, art. No. e202423296.

[21] Y.P. Wang, K.J. Zhao, K. Wang, H.H. Li, H.B. Jiang, and L. Chen, N-doped carbon confined Na₃V₂(PO₄)₃ derived from an organophosphonic acid as a high-performance cathode for sodium-ion batteries, J. Alloy. Compd., 844(2020), art. No. 156118.

[22] Chen M, Shao LL, Yang HB, Ren TZ, Du GH, Yuan ZY. Vanadium-doping of LiFePO₄/carbon composite cathode materials synthesized with organophosphorus source. Electrochim. Acta, 2015, 167: 278

[23] Chen M, Shao LL, Yang HB, Zhao QY, Yuan ZY. Organophosphonic acid as precursor to prepare LiFePO₄/carbon nanocomposites for high-power lithium ion batteries. Electrochim. Acta, 2015, 168: 59

[24] Huang JS, Yang L, Liu KY. Organic phosphoric sources for syntheses of Li₃V₂(PO₄)₃/C via improved rheological phase reaction. Mater. Lett., 2012, 66(1): 196

[25] Li Y, Wang L, Zhang KY, Yao YC, Kong LX. Optimized synthesis of LiFePO₄ cathode material and its reaction mechanism during solvothermal. Adv. Powder Technol., 2021, 32(6): 2097

[26] Lin GF, Wang Q, Yang X, Cai ZH, Xiong YZ, Huang B. Preparation of phosphorus-doped porous carbon for high performance supercapacitors by one-step carbonization. RSC Adv., 2020, 10(30): 17768

[27] Y. Zhou, Z.X. Jia, L.L. Shi, et al., Pressure difference-induced synthesis of P-doped carbon nanobowls for high-performance supercapacitors, Chem. Eng. J., 385(2020), art. No. 123858.

[28] X. Fan, H. Xu, S.S. Zuo, Z.P. Liang, S.H. Yang, and Y. Chen, Preparation and supercapacitive properties of phosphorus-doped reduced graphene oxide hydrogel, Electrochim. Acta, 330(2020), art. No. 135207.

[29] X.Y. Xu, H. Zhang, H. Yang, et al., Constructs high performance iron-based phosphate sodium-ion batteries via oxygen vacancies strategy, Chem. Eng. J., 520(2025), art. No. 166248.

[30] Y. Li, D.M. Cheng, J.Y. Tian, et al., Unlocking high lithium-ion transport in solid polymer electrolytes with dynamic hydrogen-bonded zinc–adeninate framework, Cell Rep. Phys. Sci., 6(2025), No. 6, art. No. 102624.

[31] X.Q. Li, Y. Zhang, B.L. Zhang, K. Qin, H.M. Liu, and Z.F. Ma, Mn-doped Na₄Fe₃(PO₄)₂(P₂O₇) facilitating Na⁺ migration at low temperature as a high performance cathode material of sodium ion batteries, J. Power Sources, 521(2022), art. No. 230922.

[32] H. Fan, C.C. Cai, X.B. Liao, et al., Na₄Fe_1.5Mn_1.5(PO₄)₂(P₂O₇): A low-cost and earth-abundant cathode for robust sodium storage, Mater. Today Energy, 42(2024), art. No. 101552.

[33] Nose M, Shiotani S, Nakayama H, Nobuhara K, Nakanishi S, Iba H. Na₄Co_2.4Mn_0.3Ni_0.3(PO₄)₂P₂O₇: High potential and high capacity electrode material for sodium-ion batteries. Electrochem. Commun., 2013, 34: 266

[34] R. Du, C.C. Liu, Q. Huang, et al., Simultaneous effects of C–N–V bonds and multiple sulfides anchoring active V and Na enables honeycomb-like porous Na₃V₂(PO₄)₃ with non-attenuation characteristics for Na-ion batteries, Smah, 21(2025), No. 32, art. No. 2503471.

[35] Torijano E, Vargas RA, Diosa JE, Mellander BE. High temperature phase transitions of NH₄H₂PO₄. Phys. Status Solidi B, 2000, 220(1): 659

[36] Zhang K, Wang Z, Ma SY, Wu C, Zhao XY. Theoretical study on the thermal decomposition mechanism of Fe(EDTA)⁻ and Fe(EDTMP)⁻. Molecules, 2024, 29(18): 4362

[37] C. Zhang, W. Liu, S.W. Wang, et al., Fabrication of onion-like carbon frameworks and uniform carbon coating layer at Na₄Fe₃(PO₄)₂P₂O₇ for synergistically improving conductivity and structural stability, J. Power Sources, 650(2025), art. No. 237475.

[38] S.I. Moseenkov, V.L. Kuznetsov, N.A. Zolotarev, et al., Investigation of amorphous carbon in nanostructured carbon materials (A comparative study by TEM, XPS, Raman spectroscopy and XRD), Materials, 16(2023), No. 3, art. No. 1112.

[39] Han XY, Meng XD, Chen S, et al.. P-doping a porous carbon host promotes the lithium storage performance of red phosphorus. ACSAppl. Mater. Interfaces, 2023, 15(9): 11713

[40] J.H. Mu, S.I. Wong, Q. Li, et al., Fishbone-derived N-doped hierarchical porous carbon as an electrode material for supercapacitor, J. Alloy. Compd., 832(2020), art. No. 154950.

[41] Zheng L, Xia KS, Han B, et al.. N/P co-doped porous carbon-coated graphene nanohybrid as a high-performance electrode for supercapacitors. ACS Appl. Nano Mater., 2018, 1(12): 6742

[42] C. Sun, W.S. Du, and Q. Sun, N, P co-doping for microstructural regulation of pitch-derived carbon toward high-rate sodium storage, J. Alloy. Compd., 1022(2025), art. No. 179832.

[43] S.M. Wu, C.X. Feng, B.B. Fan, Y.H. Li, H. Wang, and Y.M. Zhou, N/O/P co-doped hierarchical porous graphitic carbon materials for high-rate supercapacitors, J. Alloy. Compd., 899(2022), art. No. 163282.

[44] Liu DZ, Yang ZH, Cao YY, et al.. Pillar doping of Na4 site in Na₄Fe₃(PO₄)₂P₂O₇ alleviating structural evolution at high voltages for sodium storage. J. Energy Chem., 2025, 109: 931

[45] Zhang LM, Xiao JC, Wang JR, et al.. Active-site-specific structural engineering enabled ultrahigh rate performance of the NaLi₃Fe₃(PO₄)₂(P₂O₇) cathode for lithium-ion batteries. ACS Appl. Mater. Interfaces, 2022, 14(9): 11255

[46] Li NC, Li CW, Sedlacik M, et al.. Modulating electronic structure to expedite Na₄Fe₃(PO₄)₂P₂O₇ reaction kinetics for high-power Na-ion batteries. Rare Met., 2025, 44(11): 8444

[47] W. Wei, H.Y. Wang, K.J. Xiang, et al., A novel dual carbon source improvement strategy for optimizing the ultra-high rate performance of Na₄Fe₃(PO₄)₂P₂O₇ cathode for sodium-ion batteries, Nano Res., 18(2024), No. 6, art. No. 94907517.

[48] L.Q. Zhang, R. Sun, Y.H. Liang, et al., Carbon quantum dot dual-regulation for constructing high-performance NFPP cathode: Synergistic breakthrough in electron conductivity and ion transport, Energy Storage Mater., 81(2025), art. No. 104548.

[49] Y. Shao, C.Y. Liu, H.M. Fan, et al., Phase- purity stoichiometric Na₄Fe₃(PO₄)₂P₂O₇ cathode material via reversible reaction modulation for high-performance sodium-ion batteries, Small, 21(2025), No. 33, art. No. 2504847.

[50] W.H. Song, M. Lei, J. Peng, et al., Phase composition optimization and performance improvement of Na₄Fe₃(PO₄)₂P₂O₇ for high rate capability sodium-ion batteries, J. Energy Storage, 136(2025), art. No. 118507.

[51] F.Y. Xiong, J.T. Li, C.L. Zuo, et al., Mg-doped Na₄Fe₃(PO₄)₂(P₂O₇)/C composite with enhanced intercalation pseudocapacitance for ultra-stable and high-rate sodium-ion storage, Adv. Funct. Mater., 33(2023), No. 6, art. No. 2211257.

[52] Chen XL, Zheng YH, Liu WJ, Zhang C, Li S, Li J. High-performance sodium-ion batteries with a hard carbon anode: Transition from the half-cell to full-cell perspective. Nanoscale, 2019, 11(46): 22196

[53] Y.X. Jia, S.H. Li, Z. Wang, et al., Tailoring nanostructured Na₄Fe₃(PO₄)₂P₂O₇ cathode with high phase purity for ultrahighrate and long-life sodium-ion batteries, J. Power Sources, 652(2025), art. No. 237708.

Rights & permissions

University of Science and Technology Beijing

Just Accepted

This article has successfully passed peer review and final editorial review, and will soon enter typesetting, proofreading and other publishing processes. The currently displayed version is the accepted final manuscript. The officially published version will be updated with format, DOI and citation information upon launch. We recommend that you pay attention to subsequent journal notifications and preferentially cite the officially published version. Thank you for your support and cooperation.