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Instruments / Technical Area	Publication Details	Published	Actions
I09-Surface and Interface Structural Analysis	Improved cycling stability in high-capacity Li-rich vanadium containing disordered rock salt oxyfluoride cathodes Christian Baur , Ida Kallquist , Johann Chable , Jin Hyun Chang , Rune E. Johnsen , Francisco Ruiz-zepeda , Jean-marcel Ateba Mba , Andrew Naylor , Juan Maria Garcia-lastra , Tejs Vegge , Franziska Klein , Annika R. Schür , Poul Norby , Kristina Edström , Maria Hahlin , Maximilian Fichtner Journal Of Materials Chemistry A 7, 21244 - 21253 DOI: 10.1039/C9TA06291B Diamond Proposal Number(s): [19602] Open Access Show Abstract ▼ 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.	Sep 2019
I09-Surface and Interface Structural Analysis	Degradation mechanisms in Li 2 VO 2 F Li-rich disordered rock-salt cathodes Ida Kallquist , Andrew J. Naylor , Christian Baur , Johann Chable , Jolla Kullgren , Maximilian Fichtner , Kristina Edstrom , Daniel Brandell , Maria Hahlin Chemistry Of Materials DOI: 10.1021/acs.chemmater.9b00829 Diamond Proposal Number(s): [19602] Show Abstract ▼ Abstract: The strive for increased energy density in Li-ion batteries is particularly dependent on the cathode materials, that so far have been limiting for the overall battery performance. A new class of materials, Li-rich disordered rock-salts, has recently been brought forward as promising candidates for next-generation cathodes due to their ability to reversibly cycle more than one Li-ion per transition metal. Several variants of these Li-rich cathode materials have been developed recently and show promising initial capacities, but challenges concerning capacity fade and voltage decay during cycling need yet to be overcome. Mechanisms behind the significant capacity fade of some materials must be understood to allow for the design of new materials in which detrimental reactions can be mitigated. In this study the origin of the capacity fade in the Li-rich material Li2VO2F is investigated and it is shown to begin with a degradation of the particle surface that spreads inwards with continued cycling.	Jun 2019

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