In order to analyse and characterize the materials synthesized in the group (or through collaborations), we have been utilizing in depth various spectroscopies. By carrying out X-Ray Absorption Spectroscopy (XAS) experiments on a synchrotron, we are able to study samples which may sometimes be quite thick (such as batteries during their cycling process) and, with a remarkable time and energy resolution, we can probe all electronic levels (even the very deep ones). In case of need for high spatial resolution, Electron Energy-Loss Spectroscopy (EELS) is used extensively (on nano-composite materials for example) and is also developed to study edges at low energy such as the lithium K edge. Last spectroscopy but not least, Nuclear Magnetic Resonance (NMR) is utilized to identify crystallographically equivalent sites (distinct vanadium sites in Li1,1V3O8), to study local distortions or obtain some insight on charge transfers. Complementing these spectroscopic measurements, electronic structure calculations based on first-principles (DFT essentially) are performed to simulate the experimental spectra. We can then interpret the changes observed, with a special attention to the chemical bonding and the atomic structure changes (during lithium intercalation for example). The same calculations can also be used to complement structural studies carried out with X-Ray diffraction.
Our research is consequently split in four main themes, which are in fact pretty much connected to each other.
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