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Vanadium Oxyfluoride/Few-Layer Graphene Composite as a High-Performance Cathode Material for Lithium Batteries

Cambaz, Musa Ali and Vinayan, B. P. and Clemens, Oliver and Munnangi, Anji Reddy and Chakravadhanula, Venkata Sai Kiran and Kübel, Christian and Fichtner, Maximilian (2016):
Vanadium Oxyfluoride/Few-Layer Graphene Composite as a High-Performance Cathode Material for Lithium Batteries.
In: Inorganic Chemistry, American Chemical Society, pp. 3789-3796, 55, (8), ISSN 0020-1669,
DOI: 10.1021/acs.inorgchem.5b02687,
[Online-Edition: https://doi.org/10.1021/acs.inorgchem.5b02687],
[Article]

Abstract

Metal oxyfluoride compounds are gathering significant interest as cathode materials for lithium ion batteries at the moment because of their high theoretical capacity and resulting high energy density. In this regard, a new and direct approach is presented to synthesize phase-pure vanadium oxyfluoride (VO2F). The structure of VO2F was identified by Rietveld refinement of the powder X-ray diffraction (XRD) pattern. It crystallizes in a perovskite-type structure with disorder of the oxide and fluoride ions. The as-synthesized VO2F was tested as a cathode material for lithium ion batteries after being surface-coated with few-layer graphene. The VO2F delivered a first discharge capacity of 254 mA h g–1 and a reversible capacity of 208 mA h g–1 at a rate of C/20 for the first 20 cycles with an average discharge voltage of 2.84 V, yielding an energy density of 591 W h kg–1. Improved rate capability that outperforms the previous report has been achieved, showing a discharge capacity of 150 mA h g–1 for 1 C. The structural changes during lithium insertion and extraction were monitored by ex-situ XRD analysis of the electrodes discharged and charged to various stages. Lithium insertion results in an irreversible structural change of the anion lattice from 3/4 cubic close packing to hexagonal close packing to accommodate the inserted lithium ions while keeping the overall space-group symmetry. For the first time we have revealed a structural change for the ReO3-type structure of as-prepared VO2F to the RhF3 structure after lithiation/delithiation, with structural changes that have not been observed in previous reports. Furthermore, the new synthetic approach described here would be a platform for the synthesis of new oxyfluoride compounds.

Item Type: Article
Erschienen: 2016
Creators: Cambaz, Musa Ali and Vinayan, B. P. and Clemens, Oliver and Munnangi, Anji Reddy and Chakravadhanula, Venkata Sai Kiran and Kübel, Christian and Fichtner, Maximilian
Title: Vanadium Oxyfluoride/Few-Layer Graphene Composite as a High-Performance Cathode Material for Lithium Batteries
Language: English
Abstract:

Metal oxyfluoride compounds are gathering significant interest as cathode materials for lithium ion batteries at the moment because of their high theoretical capacity and resulting high energy density. In this regard, a new and direct approach is presented to synthesize phase-pure vanadium oxyfluoride (VO2F). The structure of VO2F was identified by Rietveld refinement of the powder X-ray diffraction (XRD) pattern. It crystallizes in a perovskite-type structure with disorder of the oxide and fluoride ions. The as-synthesized VO2F was tested as a cathode material for lithium ion batteries after being surface-coated with few-layer graphene. The VO2F delivered a first discharge capacity of 254 mA h g–1 and a reversible capacity of 208 mA h g–1 at a rate of C/20 for the first 20 cycles with an average discharge voltage of 2.84 V, yielding an energy density of 591 W h kg–1. Improved rate capability that outperforms the previous report has been achieved, showing a discharge capacity of 150 mA h g–1 for 1 C. The structural changes during lithium insertion and extraction were monitored by ex-situ XRD analysis of the electrodes discharged and charged to various stages. Lithium insertion results in an irreversible structural change of the anion lattice from 3/4 cubic close packing to hexagonal close packing to accommodate the inserted lithium ions while keeping the overall space-group symmetry. For the first time we have revealed a structural change for the ReO3-type structure of as-prepared VO2F to the RhF3 structure after lithiation/delithiation, with structural changes that have not been observed in previous reports. Furthermore, the new synthetic approach described here would be a platform for the synthesis of new oxyfluoride compounds.

Journal or Publication Title: Inorganic Chemistry
Volume: 55
Number: 8
Publisher: American Chemical Society
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Fachgebiet Materialdesign durch Synthese
11 Department of Materials and Earth Sciences > Material Science > Joint Research Laboratory Nanomaterials
Date Deposited: 12 Apr 2017 12:08
DOI: 10.1021/acs.inorgchem.5b02687
Official URL: https://doi.org/10.1021/acs.inorgchem.5b02687
Funders: Financial support by EU-RTD “Hi-C” (“Novel in situ and in operando techniques for characterization of interfaces in electrochemical storage systems”) in the Seventh FP (Grant Agreement 608575) is gratefully acknowledged., O.C. gratefully acknowledges the support from the German Science Foundation (DFG, Deutsche Forschungsgemeinschaft, Emmy Noether Research Grant, CL 551/2-1).
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