Improved cycling stability in high-capacity Li-rich vanadium containing disordered rock salt oxyfluoride cathodes

Christian Baur*, Ida Källquist, Johann Chable, Jin Hyun Chang, Rune E. Johnsen, Francisco Ruiz-Zepeda, Jean-Marcel Ateba Mba, Andrew J. Naylor, Juan Maria García-Lastra, Tejs Vegge, Franziska Klein, Annika R. Schür, Poul Norby, Kristina Edström, Maria Hahlin, Maximilian Fichtner

*Corresponding author for this work

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Abstract

Lithium-rich transition metal disordered rock salt (DRS) oxyfluorides have the potential to lessen one large bottleneck for lithium ion batteries by improving the cathode capacity. However, irreversible reactions at the electrode/electrolyte interface have so far led to fast capacity fading during electrochemical cycling. Here, we report the synthesis of two new Li-rich transition metal oxyfluorides Li2V0.5Ti0.5O2F and Li2V0.5Fe0.5O2F using the mechanochemical ball milling procedure. Both materials show substantially improved cycling stability compared to Li2VO2F. Rietveld refinements of synchrotron X-ray diffraction patterns reveal the DRS structure of the materials. Based on density functional theory (DFT) calculations, we demonstrate that substitution of V3+ with Ti3+ and Fe3+ favors disordering of the mixed metastable DRS oxyfluoride phase. Hard X-ray photoelectron spectroscopy shows that the substitution stabilizes the active material electrode particle surface and increases the reversibility of the V3+/V5+ redox couple. This work presents a strategy for stabilization of the DRS structure leading to improved electrochemical cyclability of the materials.
Original languageEnglish
JournalJournal of Materials Chemistry A
Volume7
Issue number37
Pages (from-to)21244-21253
ISSN2050-7488
DOIs
Publication statusPublished - 2019

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