Comprehensive Insights into the Structural and Chemical Changes in Mixed-Anion FeOF Electrodes by Using Operando PDF and NMR Spectroscopy
- 22 February 2013
- journal article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 135 (10), 4070-4078
- https://doi.org/10.1021/ja400229v
Abstract
In-depth analysis of operando X-ray pair distribution function (PDF) data is combined with Li NMR spectroscopy to gain comprehensive insights into the electrochemical reaction mechanism of high-performance iron oxyfluoride electrodes. While the full discharge capacity could be recovered upon charge, implying reversibility of the electrochemical reaction, the atomic structure of the electrode formed after cycling (discharge–charge) differs from the pristine uncycled electrode material. Instead, the “active” electrode that forms upon cycling is a nanocomposite of an amorphous rutile phase and a nanoscale rock salt phase. Bond valence sum analysis, based on the precise structural parameters (bond lengths and coordination number) extracted from the in situ PDF data, suggests that anion partitioning occurs during the electrochemical reaction, with the rutile phase being F-rich and the rock salt phase being O-rich. The F- and O-rich phases react sequentially; Fe in a F-rich environment reacts preferentially during both discharge and charge.Keywords
This publication has 34 references indexed in Scilit:
- Recent Progress in Nanostructured Cathode Materials for Lithium Secondary BatteriesAdvanced Functional Materials, 2010
- Beyond Intercalation‐Based Li‐Ion Batteries: The State of the Art and Challenges of Electrode Materials Reacting Through Conversion ReactionsAdvanced Materials, 2010
- Real-Time NMR Investigations of Structural Changes in Silicon Electrodes for Lithium-Ion BatteriesJournal of the American Chemical Society, 2009
- Iron Oxyfluorides as High Capacity Cathode Materials for Lithium BatteriesJournal of the Electrochemical Society, 2009
- Nanostructured materials for advanced energy conversion and storage devicesNature Materials, 2005
- Carbon-Metal Fluoride NanocompositesJournal of the Electrochemical Society, 2003
- Nonstoichiometric, Rutile-Type, Solid Solutions in the FeIIF2–FeIIIOF SystemJournal of Solid State Chemistry, 2001
- An Electron Diffraction and Crystal Chemical Investigation of Oxygen/Fluorine Ordering in Rutile-Type Iron Oxyfluoride, FeOFJournal of Solid State Chemistry, 2000
- Nano-sized transition-metal oxides as negative-electrode materials for lithium-ion batteriesNature, 2000
- The refinement of the crystal structure of iron oxyfluoride, FeOFJournal of Solid State Chemistry, 1973