| Autor: |
Stephanie F. Linnell, Eun Jeong Kim, Yong-Seok Choi, Moritz Hirsbrunner, Saki Imada, Atin Pramanik, Aida Fuente Cuesta, David N. Miller, Edoardo Fusco, Bela E. Bode, John T. S. Irvine, Laurent C. Duda, David O. Scanlon, A. Robert Armstrong |
| Přispěvatelé: |
EPSRC, University of St Andrews. School of Chemistry, University of St Andrews. Biomedical Sciences Research Complex, University of St Andrews. Centre of Magnetic Resonance, University of St Andrews. EaSTCHEM, University of St Andrews. Centre for Energy Ethics, University of St Andrews. Centre for Designer Quantum Materials |
| Jazyk: |
angličtina |
| Rok vydání: |
2022 |
| Předmět: |
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| Popis: |
L. D. gratefully acknowledges financial support from the Swedish Energy Agency (contract 2020-005246). Y.C. and D.O.S. are grateful to the Faraday Institution for funding the MICHAEL computing cluster hosted at University College London (UCL). Our membership of the UKs HEC Materials Chemistry Consortium, which is funded by EPSRC (EP/L000202, EP/R029431), this work used the ARCHER2 UK National Supercomputing Service(http://www.archer2.ac.uk). We are also grateful to the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (EP/P020194/1 and EP/T022213/1). We are grateful to the Engineering and Physical Sciences Research Council (EPSRC) Light Element Facility Grant (EP/T019298/1) for funding the acquisition of the Raman spectrometer. EF is grateful for an EaStCHEM studentship. This work was supported by the Faraday Institution (grant number FIRG018). Anion redox reactions offer a means of enhancing the capacity of layered sodium transition metal oxide positive electrode materials. However, oxygen redox reactions typically show limited reversibility and irreversible structural changes upon cycling, resulting in rapid capacity loss. Here, the Ti substituted Na4/7[□1/7Ti1/7Mn5/7]O2 (where □ represents a transition metal vacancy) is presented as a positive electrode material for sodium ion batteries. Na4/7[□1/7Ti1/7Mn5/7]O2 delivers a reversible capacity of 167 mAh g -1 after 25 cycles at 10 mA g -1 within the voltage range of 1.6 – 4.4 V and presents enhanced stability compared with Na4/7[□1/7Mn6/7]O2 over the voltage range 3.0 – 4.4 V. The structural and electronic structural changes of this Ti4+ substituted phase are investigated by powder X-ray diffraction, X ray absorption spectroscopy, electron paramagnetic resonance and Raman spectroscopy, supported by density functional theory calculations. These results show that the Na4/7[□1/7Mn6/7]O2 structure is maintained between 3.0 – 4.4 V, and the presence of TiO6 octahedra in Na4/7[□1/7Ti1/7Mn5/7]O2 relieves structural distortions from Jahn Teller distorted Mn3+O6 between 1.6 – 4.4 V. Furthermore, Ti4+ substitution stabilises the adjacent O 2p orbitals and raises the ionicity of the Mn O bonds, increasing the operating potential of Na4/7[□1/7Ti1/7Mn5/7]O2. Thereby providing evidence that the improved electrochemical performance of Na4/7[□1/7Ti1/7Mn5/7]O2 can be attributed to Ti4+ substitution. This work provides insight and strategies for improving the structural stability and electrochemical performance of sodium layered oxides. Publisher PDF |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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