Solving the Structure of Li Ion Battery Materials with Precession Electron Diffraction: Application to Li2CoPO4F - Short summary of the paper
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The document discusses the successful refinement of the structure of Li2CoPO4F using precession electron diffraction, which could not be resolved using bulk diffraction methods. It outlines the procedure, including the extraction of peak intensities and the application of direct methods to locate Li, O, and F atoms. The conclusion emphasizes the effectiveness of precession electron diffraction for characterizing lithium-based battery materials.
Solving the Structure of Li Ion Battery Materials with Precession Electron Diffraction: Application to Li2CoPO4F - Short summary of the paper
- 2. The problem: Structure of Li2CoPO4F cannot be solved or refined from bulk diffraction. The solution: Precession electron diffraction càn get the job done. This presentation describes the procedure in the shortest way possible.
- 3. For a more detailed treatment: “Solving the Structure of Li Ion Battery Materials with Precession Electron Diffraction: Application to Li 2CoPO4F” in Chemistry of Materials by Joke Hadermann, Artem M. Abakumov, Stuart Turner, Zainab Hafideddine, Nellie R. Khasanova, Evgeny V. Antipov and Gustaaf Van Tendeloo Published online July 11, 2011 http://pubs.acs.org/doi/abs/10.1021/cm201257b
- 4. First, electron diffraction patterns are taken, using the precession attachment. Non main zones have more reliable peak intensities than main zones.
- 5. All patterns can be indexed using the cell parameters and space groups known from XRD: a= 10.452(2) Å, b= 6.3911(8) Å, c=10.874(2) Å Pnma
- 6. The intensities of the observed peaks are extracted (ELD software). Treated: symmetry equivalent reflections merged, geometric corrections applied Merged into one list (Triple software) We now have intensities of 237 symmetry unique reflections
- 7. a= 10.452(2) Å, Intensities of 237 b= 6.3911(8) Å, & symmetry unique c=10.874(2) Å reflections Pnma INTO Direct Methods
- 8. Result: R=31% CO and P positions similar to Li2FePO4F but Li, O, F mixed over remaining positions Assign F: tetrahedra around P O: complete the octahedra around Co Remaining positions (purple) Li or ghosts? Difference Fourier maps including Co,P,O,F
- 9. The difference Fourier maps clearly show the real peaks The Li-atoms are now also located
- 10. Straight from direct methods: too many Li(?) peaks Difference Fourier allows to eliminate the grey ones Structure is solved !
- 12. Separate list of intensities per zone were put into Jana using separate scale factors for each list on input & Use PO4 rigid units: 18 variables reduced to 6 R=24% (reasonable for precession electron diffraction data)
- 14. Conclusion Li2CoPO4F was successfully solved and refined from precession electron diffraction PED can be successfully applied for the crystallographic characterization of Li-based battery materials