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| Naji, M. |
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| Motta, Antonella |
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| Aletan, Dirar |
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| Mohamed, Tarek |
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| Ertürk, Emre |
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| Taccardi, Nicola |
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| Kononenko, Denys |
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| Petrov, R. H. | Madrid |
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| Alshaaer, Mazen | Brussels |
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| Bih, L. |
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| Casati, R. |
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| Muller, Hermance |
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| Kočí, Jan | Prague |
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| Šuljagić, Marija |
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| Kalteremidou, Kalliopi-Artemi | Brussels |
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| Azam, Siraj |
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| Ospanova, Alyiya |
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| Ali, M. A. |
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| Rančić, M. |
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| Ollier, Nadège |
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| Azevedo, Nuno Monteiro |
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| Landes, Michael |
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| Rignanese, Gian-Marco |
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Armstrong, Anthony Robert
University of St Andrews
in Cooperation with on an Cooperation-Score of 37%
Topics
Publications (6/6 displayed)
- 2023K2Fe(C2O4)2citations
- 2023Manipulating O3/P2 phase ratio in bi-phasic sodium layered oxides via ionic radius controlcitations
- 2022Importance of superstructure in stabilizing oxygen redox in P3- Na0.67Li0.2Mn0.8O2citations
- 2020Vacancy enhanced oxygen redox reversibility in P3-type magnesium doped sodium manganese oxide Na0.67Mg0.2Mn0.8O2citations
- 2014Lithium-ion diffusion mechanisms in the battery anode material Li1+xV1-xO2citations
- 2014Polymorphism in Li2MSiO4 ( M = Fe, Mn)citations
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article
Vacancy enhanced oxygen redox reversibility in P3-type magnesium doped sodium manganese oxide Na0.67Mg0.2Mn0.8O2
Abstract
Lithium-rich layered oxides and sodium layered oxides represent attractive positive electrode materials exhibiting excess capacity delivered by additional oxygen redox activity. However, structural degradation in the bulk and detrimental reactions with the electrolyte on the surface often occur, leading to limited reversibility of oxygen redox processes. Here we present the properties of P3-type Na<sub>0.67</sub>Mg<sub>0.2</sub>Mn<sub>0.8</sub>O<sub>2</sub> synthesized under both air and oxygen. Both materials exhibit stable cycling performance in the voltage range 1.8-3.8 V where the Mn<sup>3+</sup>/Mn<sup>4+</sup> redox couple entirely dominates the electrochemical reaction. Oxygen redox activity is triggered for both compounds in the wider voltage window 1.8-4.3 V with typical large voltage hysteresis from non-bonding O 2p states generated by substituted Mg. Interestingly, for the compound prepared under oxygen, an additional reversible oxygen redox activity is shown with exceptionally small voltage hysteresis (20 mV). The presence of vacancies in the transition metal layers is shown to play a critical role not only in forming unpaired O 2p states independent of substituted elements but also in stabilising the P3 structure during charge with reduced structural transformation to the O’3 phase at the end of discharge. This study reveals the important role of vacancies in P3-type sodium layered oxides to increase energy density using both cationic and anionic redox processes.