Fast oxygen redox enabled by flexible Al–O bonds in P2-type layered oxides for sodium batteries

Abstract

Sodium-ion batteries (SIBs) exhibit significant potential for large-scale energy storage systems due to the abundance and low cost of sodium resources. Triggering lattice oxygen redox (LOR) in P2-type transition metal oxides is considered a promising approach to enhance energy density in SIB cathodes, providing high operating potential and substantial capacity. However, irreversible phase transitions associated with LOR, particularly from prisms (P-type stacking) to octahedrons (O-type stacking), lead to severe structural distortions and sluggish Na⁺ diffusion kinetics. In this work, an Al-substitution strategy is proposed to suppress the formation of O-type stacking and instead promote the formation of a beneficial Z phase. The flexible Al–O bonds accommodate asymmetric variations in their occupied states during the sodiation process, mitigating local structural distortions through Al–O bond contraction. Stabilization of the local structure ensures the maintenance of a robust Na⁺ diffusion pathway. As a result, the Al-substituted cathode achieves a low Na⁺ diffusion barrier of 0.47 eV and delivers a capacity of 86 mAh/g even at a high current density of 1 A/g within 1.5–4.5 V, maintaining 62.5% capacity retention over 100 cycles.

Graphical abstract

Keywords

Al-substitution / phase transitions / local structure / sodium diffusion kinetics / lattice oxygen redox

References

[1] Wang J , Zhu Y F , Su Y . . Routes to high-performance layered oxide cathodes for sodium-ion batteries. Chemical Society Reviews, 2024, 53(8): 4230–4301

[2] Zhang F , He B , Xin Y . . Emerging chemistry for wide-temperature sodium-ion batteries. Chemical Reviews, 2024, 124(8): 4778–4821

[3] Cai X , Wang N , Liang L . . Fast oxygen redox kinetics induced by CoO₆ octahedron with π-interaction in P2-type sodium oxides. Advanced Functional Materials, 2024, 34(51): 2409732

[4] Zhang Z , Zhang H , Wu Y . . Advances in doping strategies for sodium transition metal oxides cathodes: A review. Frontiers in Energy, 2024, 18(2): 141–159

[5] Shadike Z , Chen Y , Liu L . . Improved cyclic stability of LiNi_0.8Mn_0.1Co_0.1O₂ cathode enabled by a novel CEI forming additive. Frontiers in Energy, 2024, 18(4): 535–544

[6] Yang C , Mu X Y . Mapping the trends and prospects of battery cathode materials based on patent landscape. Frontiers in Energy, 2023, 17(6): 822–832

[7] Zhao C , Wang Q , Yao Z P . . Rational design of layered oxide materials for sodium-ion batteries. Science, 2020, 370: 708–711

[8] Fouassier C , Delmas C . Evolution structurale et proprietes physiques des phases A_xMO₂ (A=Na, K; M=Cr, Mn, Co) (x ≤ 1). Materials Research Bulletin, 1975, 10: 443–450

[9] Cai X , Shadike Z , Wang N . . Oxygen redox chemistry: A new approach to high energy density world. Next Materials, 2024, 2: 100086

[10] Yu L , Hu C , Wu X . . Strong correlation between ion-migration generated vacancies and anion redox activity in layered oxides. ACS Energy Letters, 2025, 10(2): 668–677

[11] Wang X , Zhang Q , Zhao C . . Achieving a high-performance sodium-ion pouch cell by regulating intergrowth structures in a layered oxide cathode with anionic redox. Nature Energy, 2024, 9(2): 184–196

[12] Liu H , Zhao C , Wu X . . Inconsistency between superstructure stability and long-term cyclability of oxygen redox in Na layered oxides. Energy & Environmental Science, 2024, 17(2): 668–679

[13] House R A , Maitra U , Pérez-Osorio M A . . Superstructure control of first-cycle voltage hysteresis in oxygen-redox cathodes. Nature, 2019, 577(7791): 502–508

[14] Maitra U , House R A , Somerville J W . . Oxygen redox chemistry without excess alkali-metal ions in Na_2/3[Mg_0.28Mn_0.72]O₂. Nature Chemistry, 2018, 10(3): 288–295

[15] Huang Y , Zhu Y , Nie A . . Enabling anionic redox stability of P2-Na_5/6Li_1/4Mn_3/4O₂ by Mg substitution. Advanced Materials, 2022, 34(9): 2105404

[16] Li N , Zhao E , Zhang Z . . Gradient and de-clustered anionic redox enabled undetectable O₂ formation in 4.5 V sodium manganese oxide cathodes. Advanced Materials, 2024, 36(48): 2408984

[17] Rong X , Hu E , Lu Y . . Anionic redox reaction-induced high-capacity and low-strain cathode with suppressed phase transition. Joule, 2019, 3(2): 503–517

[18] Mo Y , Ong S P , Ceder G . Insights into diffusion mechanisms in P2 layered oxide materials by first-principles calculations. Chemistry of Materials, 2014, 26(18): 5208–5214

[19] Cai X , Shadike Z , Wang N . . Constraining interlayer slipping in P2-type layered oxides with oxygen redox by constructing strong covalent bonds. Journal of the American Chemical Society, 2025, 147(7): 5860–5870

[20] Cheng C , Zhuo Z , Xia X . . Stabilized oxygen vacancy chemistry toward high-performance layered oxide cathodes for sodium-ion batteries. ACS Nano, 2024, 18(51): 35052–35065

[21] Toby B H , Von Dreele R B . GSAS-II: The genesis of a modern open-source all purpose crystallography software package. Journal of Applied Crystallography, 2013, 46(2): 544–549

[22] Ravel B , Newville M . Athena, Artemis, Hephaestus: Data analysis for X-ray absorption spectroscopy using IFEFFIT. Journal of Synchrotron Radiation, 2005, 12(4): 537–541

[23] Kresse G , Furthmuller J . Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Physical Review. B, 1996, 54: 11169–11186

[24] Blöchl P E . Projector augmented-wave method. Physical Review. B, 1994, 50(24): 17953–17979

[25] Kresse G , Joubert D . From ultrasoft pseudopotentials to the projector augmented-wave method. Physical Review. B, 1999, 59: 1758–1775

[26] Kresse G , Furthmiiller J . Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Computational Materials Science, 1996, 6: 15–50

[27] Sancho-García J C , Brédas J L , Cornil J . Assessment of the reliability of the Perdew–Burke–Ernzerhof functionals in the determination of torsional potentials in π-conjugated molecules. Chemical Physics Letters, 2003, 377(1-2): 63–68

[28] Sun C , Wang Y , Zou J . . A formation mechanism of oxygen vacancies in a MnO₂ monolayer: A DFT + U study. Physical Chemistry Chemical Physics, 2011, 13(23): 11325–11328

[29] Stausholm-Møller J , Kristoffersen H H , Hinnemann B . . DFT+U study of defects in bulk rutile TiO₂. Journal of Chemical Physics, 2010, 133(14): 144708

[30] Grimme S , Antony J , Ehrlich S . . A consistent and accurateab initioparametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. Journal of Chemical Physics, 2010, 132(15): 154104

[31] Henkelman G , Jónsson H . Improved tangent estimate in the nudged elastic band method for finding minimum energy paths and saddle points. Journal of Chemical Physics, 2000, 113(22): 9978–9985

[32] Henkelman G , Uberuaga B P , Jónsson H . A climbing image nudged elastic band method for finding saddle points and minimum energy paths. Journal of Chemical Physics, 2000, 113(22): 9901–9904

[33] Nelson R , Ertural C , George J . . Lobster: Local orbital projections, atomic charges, and chemical-bonding analysis from projector-augmented-wave-based density-functional theory. Journal of Computational Chemistry, 2020, 41(21): 1931–1940

[34] Dong H , Liu H , Guo Y J . . Lithium orbital hybridization chemistry to stimulate oxygen redox with reversible phase evolution in sodium-layered oxide cathodes. Journal of the American Chemical Society, 2024, 146(32): 22335–22347

[35] Li X L , Bao J , Shadike Z . . Stabilizing transition metal vacancy induced oxygen redox by Co²⁺/Co³⁺ redox and sodium-site doping for layered cathode materials. Angewandte Chemie International Edition, 2021, 60(40): 22026–22034

[36] Assat G , Tarascon J M . Fundamental understanding and practical challenges of anionic redox activity in Li-ion batteries. Nature Energy, 2018, 3(5): 373–386

[37] Xie Y , Saubanère M , Doublet M L . Requirements for reversible extra-capacity in Li-rich layered oxides for Li-ion batteries. Energy & Environmental Science, 2017, 10(1): 266–274

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