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

DOI: 10.1039/C9TA06291B DOI Help

Authors: Christian Baur (Helmholtz Institute Ulm for Electrochemical Energy Storage) , Ida Kallquist (Uppsala University) , Johann Chable (Helmholtz Institute Ulm for Electrochemical Energy Storage) , Jin Hyun Chang (Technical University of Denmark) , Rune E. Johnsen (Technical University of Denmark) , Francisco Ruiz-zepeda (National Institute of Chemistry, Slovenia) , Jean-marcel Ateba Mba (National Institute of Chemistry, Slovenia) , Andrew Naylor (Technical University of Denmark) , Juan Maria Garcia-lastra (Technical University of Denmark) , Tejs Vegge (Technical University of Denmark) , Franziska Klein (Helmholtz Institute Ulm for Electrochemical Energy Storage) , Annika R. Schür (Helmholtz Institute Ulm for Electrochemical Energy Storage) , Poul Norby (Technical University of Denmark) , Kristina Edström (Technical University of Denmark) , Maria Hahlin (Uppsala University) , Maximilian Fichtner (Helmholtz Institute Ulm for Electrochemical Energy Storage; Karlsruhe Institute for Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Materials Chemistry A , VOL 7 , PAGES 21244 - 21253

State: Published (Approved)
Published: September 2019
Diamond Proposal Number(s): 19602

Open Access Open Access

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.

Subject Areas: Materials, Chemistry, Energy


Instruments: I09-Surface and Interface Structural Analysis

Other Facilities: Advanced Photon Source; BESSY II

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