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Toward Better Stability and Reversibility of the Mn$^{4+}$/Mn$^{2+}$Double Redox Activity in Disordered Rocksalt Oxyfluoride Cathode Materials

Shirazi Moghadam, Y.; El Kharbachi, A.; Diemant, T.; Melinte, G.; Hu, Y.; Fichtner, M.


Cation-disordered rocksalt (DRS) materials have shown good initial reversibility and facile Li$^{+}$insertion and extraction in the structure at high rates. However, all of the Li-rich oxyfluorides introduced so far suffer from short cycle lifetimes and severe capacity fading. In the current study, we combine the strategy of using high-valent cations with partial substitution of oxygen anions by fluorine ions to achieve the optimal Mn$^{4+}$/Mn$^{2+}$ double redox reaction in the composition system Li$_{2}$Mn$_{1-x}$Ti$_{x}$O$_{2}$F (0 ≤ x ≤ 2/3). While Ti-rich compositions correlate to an O-oxidation plateau and a partial Mn$^{3+}$–Mn$^{4+}$ redox process at high voltages, owing to the presence of Ti3+ in the structure, a new composition Li$_{2}$Mn$_{2/3}$Ti$_{1/3}$O$_{2}$F with a lower amount of Ti shows better electrochemical performance with an initial high discharge capacity of 227 mAh g$^{-1}$ (1.5–4.3 V window) and a Coulombic efficiency of 82% after 200 cycles with a capacity of 136 mAh g$^{-1}$ (>462 Wh kg$^{-1}$). The structural characteristics, oxidation states, and charge-transfer mechanism have been examined as a function of composition and state of charge. ... mehr

Verlagsausgabe §
DOI: 10.5445/IR/1000140727
Veröffentlicht am 15.12.2021
DOI: 10.1021/acs.chemmater.1c02334
Zitationen: 14
Web of Science
Zitationen: 13
Zitationen: 13
Cover der Publikation
Zugehörige Institution(en) am KIT Helmholtz-Institut Ulm (HIU)
Institut für Nanotechnologie (INT)
Publikationstyp Zeitschriftenaufsatz
Publikationsdatum 18.10.2021
Sprache Englisch
Identifikator ISSN: 0897-4756, 1520-5002
KITopen-ID: 1000140727
HGF-Programm 38.02.01 (POF IV, LK 01) Fundamentals and Materials
Erschienen in Chemistry of Materials
Verlag American Chemical Society (ACS)
Band 33
Heft 21
Seiten 8235−8247
Nachgewiesen in Dimensions
Web of Science
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