Bulk O2 formation and Mg displacement explain O-redox in Na0.67Mn0.72Mg0.28O2

Boivin, Édouard; House, Robert A.; Pérez-Osorio, Miguel A.; Marie, John‐Joseph; Maitra, Urmimala; Rees, Gregory J.; Bruce, Peter G.

doi:10.1016/j.joule.2021.04.006

Cited by 54 publications

(89 citation statements)

References 34 publications

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“…Because the nominal valence of Mn in NMMO is +4 and could not be further oxidized within layered oxide cathodes, it is inferred that the charge capacity of high‐voltage plateau mainly comes from the contribution of oxygen oxidation. [ 15 ] During the discharge process, the high‐voltage plateau does not appear but is replaced by a slope line, indicating a relatively large voltage hysteresis between charging and discharging. In contrast, the first charge process of NMMCO exhibits two stages with a slope region and a 4.38 V plateau, respectively.…”

Section: Resultsmentioning

confidence: 99%

Enhancing the Reversibility of Lattice Oxygen Redox Through Modulated Transition Metal–Oxygen Covalency for Layered Battery Electrodes

et al. 2022

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Utilizing reversible lattice oxygen redox (OR) in battery electrodes is an essential strategy to overcome the capacity limitation set by conventional transition metal redox. However, lattice OR reactions are often accompanied with irreversible oxygen oxidation, leading to local structural transformations and voltage/capacity fading. Herein, it is proposed that the reversibility of lattice OR can be remarkably improved through modulating transition metal–oxygen covalency for layered electrode of Na‐ion batteries. By developing a novel layered P2‐Na0.6Mg0.15Mn0.7Cu0.15O2 electrode, it is demonstrated that the highly electronegative Cu dopants can improve the lattice OR reversibility to 95% compared to 73% for Cu‐free counterpart, as directly quantified through high‐efficiency mapping of resonant inelastic X‐ray scattering. Crucially, the large energetic overlap between Cu 3d and O 2p states dictates the rigidity of oxygen framework, which effectively mitigates the structural distortion of local oxygen environment upon (de)sodiation and leads to the enhanced lattice OR reversibility. The electrode also exhibits a completely solid‐solution reaction with an ultralow volume change of only 0.45% and a reversible metal migration upon cycling, which together ensure the improved electrochemical performance. These results emphasize the critical role of transition metal–oxygen covalency for enhancing the reversibility of lattice OR toward high‐capacity electrodes employing OR chemistry.

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Section: Resultsmentioning

confidence: 99%

Enhancing the Reversibility of Lattice Oxygen Redox Through Modulated Transition Metal–Oxygen Covalency for Layered Battery Electrodes

et al. 2022

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“…The integral areas of the sXAS pre‐edge represent different O‐oxidation systems. The change in the region between excitation energies of 532–534 eV (yellow) represents the oxidation process from O 2− to peroxide/superoxide (O 2 ) n − ( n <2) [8, 12d] . The integral areas between 534–536 eV (blue) represent the oxidation process from O 2− to molecular O 2 [12b] .…”

Section: Resultsmentioning

confidence: 99%

“…The O 2 species are molecular O 2 trapped in vacancy clusters in the material. Molecular O 2 is also present in a variety of cathode materials, such as P2‐Na 0.75 Li 0.25 Mn 0.75 O 2, [8] P2‐Na 0.67 Mn 0.72 Mg 0.28 O 2 , [12d] Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 , [12b] and Li 2 MnO 2 F [12c] . Molecular O 2 can be generated in bulk or on the surface of the cathode material.…”

Section: Introductionmentioning

confidence: 99%

Tuning Bulk O₂ and Nonbonding Oxygen State for Reversible Anionic Redox Chemistry in P2‐Layered Cathodes

Li¹,

Kong

et al. 2022

Angewandte Chemie

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Improving the reversibility of oxygen redox is quite significant for layered oxides cathodes in sodiumion batteries. Herein, we for the first time simultaneously tune bulk O 2 and nonbonding oxygen state for reversible oxygen redox chemistry in P2-Na 0.67 Mn 0.5 Fe 0.5 O 2 through a synergy of Li 2 TiO 3 coating and Li/Ti co-doping. O 2À is oxidized to molecular O 2 and peroxide (O 2 ) nÀ (n < 2) during charging. Molecular O 2 derived from transition metal (TM) migration is related to the superstructure ordering induced by Li doping. The synergy mechanism of Li 2 TiO 3 coating and Li/Ti codoping on the two O-redox modes is revealed. Firstly, Li 2 TiO 3 coating restrains the surface O 2 and inhibits O 2 loss. Secondly, nonbonding LiÀ OÀ Na enhances the reversibility of O 2À !(O 2 ) nÀ . Thirdly, Ti doping strengthens the TMÀ O bond which fixes lattice oxygen. The cationic redox reversibility is also enhanced by Li/Ti codoping. The proposed insights into the oxygen redox reversibility are insightful for other oxide cathodes.

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“…Similar oxygen-redox reactions have been intensively investigated in density functional theory (DFT) calculations of Mg-excess Mn oxide, Na 2/3 [Mg 1/3 Mn 2/3 ]O 2 . [23,24] Here in, we demonstrate that an Al 3+ incorporated Li-excess Na layered oxide (Al-NLMO) exhibits significantly improved reversibility of anion redox reaction as well as maintains nonhysteretic voltage behaviors with the selective oxygen redox. Specifically, by incorporating small amount of Al into NLMO, the ratio of charge plateau capacity to discharge plateau capacity increased from 59.3% to 74.9% for the first cycle.…”

Section: (2 Of 12)mentioning

confidence: 98%

“…The pre-edge peak at about 531 eV is attributed to electronic transition from the O 1s state to O 2p−TM 3d, which is usually examined to evaluate the activity of oxygen during the anionic redox reaction. [23,30] In both NLMO and Al-NLMO, the intensity at 531 eV increases during the charge and decreases back to initial intensity during the following discharge. It is worth noting that the change of intensity at 531 eV during charge and discharge is much bigger in Al-NLMO, which is consistent with XPS result, demonstrating higher utilization of oxygen redox in Al-NLMO compared to NLMO.…”

Section: Charge Compensation Mechanisms Of Nlmo and Al-nlmomentioning

confidence: 99%

Enabling Stable and Nonhysteretic Oxygen Redox Capacity in Li‐Excess Na Layered Oxides

Yoon

Koo

Park

et al. 2022

Advanced Energy Materials

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high-energy-density cathodes has been assigned to anion redox reaction via oxygen ions beyond the cationic redox reactions for lithium-and sodium-ion batteries (LIBs and SIBs). [1][2][3] Unfortunately, the oxygen redox reaction generally makes the oxide framework very unstable with phase transitions, resulting in various electrochemical drawbacks such as a very large voltage decay and irreversible capacity for most Li-and Na-based oxygen redox cathodes. [4][5][6] For LIBs, anomalous charge capacities delivered by oxygen redox reactions at 4.5 V (vs Li + /Li) were observed in Li 2 MnO 3 or Li 2 MnO 3 -containing layered oxides upon charging. [7][8][9] However, totally varied discharge curves were observed, which was induced by Mnmigration from the M layer to the A layer in the cathodes. [10,11] For SIBs, Na[Li 1/3 Mn 2/3 ]O 2 exhibiting the oxygen redox reaction was theoretically designed by our group based on the inspiration that redox-inactive Mn 4+ in an octahedral complex is very difficult to be further oxidized to Mn 5+ for compensating charge imbalance induced by Na-extraction in Na[Li 1/3 Mn 2/3 ]O 2 . [12,13] However, the charge voltage curve did not maintain upon discharging, indicating the severe electrochemical polarization inThe demands for higher energy density of rechargeable batteries have been continuously increasing recently, and cationic redox based current cathodes have little scope to further increase energy density since they already exhibit near-theoretical specific capacities. In this regard, oxygen redox (OR) reactions have emerged as a promising breakthrough for sodium-ion battery (SIB) cathodes. Most OR-based layered oxides suffer from drastic hystereticoxygen capacities upon discharging after the first charging. In contrast, stable and nonhysteretic oxygen capacities are herein enabled via Al 3+ incorporation into Li-excess Na layered oxide (NLMO). By combining experimental work and first-principles calculations, it is found that there is an additional stable phase during the oxygen redox for Al incorporated NLMO in comparison with bare NLMO, which is a critical factor in extending and stabilizing the discharge capacity in thermodynamics. In addition, the additional redoxinactive Al 3+ leads to heterogeneous oxygen redox rather than homogeneous, which results in stabilization of the oxide framework with sensitively control of the oxygen participation upon cycling.

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Bulk O2 formation and Mg displacement explain O-redox in Na0.67Mn0.72Mg0.28O2

Cited by 54 publications

References 34 publications

Enhancing the Reversibility of Lattice Oxygen Redox Through Modulated Transition Metal–Oxygen Covalency for Layered Battery Electrodes

Enhancing the Reversibility of Lattice Oxygen Redox Through Modulated Transition Metal–Oxygen Covalency for Layered Battery Electrodes

Tuning Bulk O₂ and Nonbonding Oxygen State for Reversible Anionic Redox Chemistry in P2‐Layered Cathodes

Enabling Stable and Nonhysteretic Oxygen Redox Capacity in Li‐Excess Na Layered Oxides

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Bulk O2 formation and Mg displacement explain O-redox in Na0.67Mn0.72Mg0.28O2

Cited by 54 publications

References 34 publications

Enhancing the Reversibility of Lattice Oxygen Redox Through Modulated Transition Metal–Oxygen Covalency for Layered Battery Electrodes

Enhancing the Reversibility of Lattice Oxygen Redox Through Modulated Transition Metal–Oxygen Covalency for Layered Battery Electrodes

Tuning Bulk O2 and Nonbonding Oxygen State for Reversible Anionic Redox Chemistry in P2‐Layered Cathodes

Enabling Stable and Nonhysteretic Oxygen Redox Capacity in Li‐Excess Na Layered Oxides

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Tuning Bulk O₂ and Nonbonding Oxygen State for Reversible Anionic Redox Chemistry in P2‐Layered Cathodes