Anionic Redox Reactions in Cathodes for Sodium‐Ion Batteries

Park, Jae Hyuk; Ko, In Hwan; Lee, Jaewoon; Park, Sang‐Eon; Kim, Duho; Yu, Seung Ho; Sung, Yung Eun

doi:10.1002/celc.202001383

Cited by 22 publications

(19 citation statements)

References 75 publications

(142 reference statements)

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“…As an example, for the P2type cathode material Na 0.78 (Li 0.25 Ni 0.75 )O 2 , isotope labeling also confirmed a significant loss of lattice oxygen by electrolyte oxidation to CO 2 , but at a potential of 5.0 V [67]. As with these materials, the intense gas evolution in the first cycle may indicate the presence of anion redox in the materials studied, which has been reported for several SIB cathode materials [68,69]. The presence, extent and reversibility of anion redox is beyond the scope of this work and will be investigated in a follow-up study.…”

Section: In Situ Gas Analysissupporting

confidence: 63%

P2-type layered high-entropy oxides as sodium-ion cathode materials

et al. 2022

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P2-type layered oxides with the general Na-deficient composition NaxTMO2 (x < 1, TM: transition metal) are a promising class of cathode materials for sodium-ion batteries. The open Na+ transport pathways present in the structure lead to low diffusion barriers and enable high charge/discharge rates. However, a phase transition from P2 to O2 structure occurring above 4.2 V, combined with metal dissolution at low potentials upon discharge, results in rapid capacity degradation. In this work, we demonstrate the positive effect of configurational entropy on the stability of the crystal structure during battery operation. Three different compositions of layered P2-type oxides were synthesized by solid-state chemistry, Na0.67(Mn0.55Ni0.21Co0.24)O2, Na0.67(Mn0.45Ni0.18Co0.24Ti0.1Mg0.03)O2, and Na0.67(Mn0.45Ni0.18Co0.18Ti0.1Mg0.03Al0.04Fe0.02)O2 with low, medium and high configurational entropy, respectively. The high-entropy cathode material shows lower structural transformation and Mn dissolution upon cycling in a wide voltage range from 1.5 to 4.6 V. Advanced operando techniques and post-mortem analysis were used to probe the underlying reaction mechanism thoroughly. Overall, the high-entropy strategy is a promising route for improving the electrochemical performance of P2 layered oxide cathodes for advanced sodium-ion battery applications.

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Section: In Situ Gas Analysissupporting

confidence: 63%

P2-type layered high-entropy oxides as sodium-ion cathode materials

et al. 2022

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“…The ratio of blue to pink is 59.3%, 55.3%, and 50.3% in NLMO, showing that the reversibility of oxygen redox reaction decreases with cycle number as reported previously. [27] This tendency is also observed in Al-NLMO, but the values are still higher than those of NLMO (74.9%, 73.7%, and 67.4% for 1st, 2nd, and 3rd cycle, respectively). As shown in Figure 2d-f, we also cycled the cells with different voltage cut-off ranges, (i) 4.1-4.4 V, (ii) 4.0-4.5 V, (iii) 4.0-4.6 V at a current density of 10 mA g −1 , and the standard deviations of charge and discharge capacities at these experimental conditions are shown in Figure S9 (Supporting Information), showing that the data obtained are reliable and reproducible.…”

Section: Anion Redox Comparison Of Nlmo and Al-nlmomentioning

confidence: 53%

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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“…The irreversible anionic redox behaviors induce a series of degradation problems, such as irreversible O 2 release, cationic migration, structural destruction, parasitic electrolyte degradation, surface reconstruction, TM reduction, and sluggish kinetic. [40,[50][51][52][53] For example, Jia et al [54] investigated oxygen-related anionic redox behaviors of the O3-Na 0.6 Li 0.2 Fe 0.4 Ru 0.4 O 2 cathode through in situ Raman and in situ differential electrochemical mass spectrometry. At the charge cutoff voltage above 4 V, the oxygen-related anionic redox was triggered, but inevitably led to the irreversible evolution of gaseous O 2 and superoxide.…”

Section: Na + /Vacancy Orderingmentioning

confidence: 99%

Structural degradation mechanisms and modulation technologies of layered oxide cathodes for sodium‐ion batteries

Song

Wang

Lee

2022

Carbon Neutralization

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Renewable energies, such as solar and wind, have been explored and widely applied for alleviating problems associated with the depletion of fossil fuel resources and environmental pollution. The intermittent and fluctuating features of these renewable energies require development of efficient energy storage and conversion systems. Sodium‐ion batteries (SIBs) are considered one of the most promising candidates for large‐scale energy storage due to the low cost and earth abundance of sodium resources. A major challenge for the practical application of SIBs is the development of appropriate cathodes with high energy densities and cycling stabilities. Layered oxide cathodes have received significant attention because of their relatively simple synthetic routes and high capacities stemming from their layered structures. However, they often suffer from moisture sensitivity and structural degradation upon repeated Na+ insertion/extraction, leading to severe performance fading. This review summarizes and discusses the degradation mechanisms of these layered oxide cathodes and modulation strategies for addressing the stability issues. Understanding the mechanisms behind structural instability would provide better insight for improving SIBs' cathode materials, which has critical implications for the designs and applications of SIBs as renewable energy systems.

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Anionic Redox Reactions in Cathodes for Sodium‐Ion Batteries

Cited by 22 publications

References 75 publications

P2-type layered high-entropy oxides as sodium-ion cathode materials

P2-type layered high-entropy oxides as sodium-ion cathode materials

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

Structural degradation mechanisms and modulation technologies of layered oxide cathodes for sodium‐ion batteries

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