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#1 23.05.2013 20:21:52

Откуда: КНУ, химфак
Здесь с 15.05.2005
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PhD - position available - Combined NMR and calculations study ofLiM

PhD - position available - Combined NMR and calculations study ofLiM(XO4)F (M = transition metal and X= P, S) positive electrode materials for Li-ion batteries

A 3-year Ph-D grant is available starting September or October 2013 at Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB)-CNRS, PESSAC (France).

Supervisors: Michel Ménétrier and Dany Carlier
Combined NMR and calculations study of LiM(XO4)F (M = transition metal and X= P, S) positive electrode materials for Li-ion batteries

The French ANR « HIPOLITE » project tackles the problems remaining with new chemistries for Li-ion Batteries in the LiMXO4F (M = Fe, V, Mn, X = P, S) families by combining basic science and prototyping. It gathers four partner labs (LRCS (Amiens), ICMCB (Bordeaux), ICG (Montpellier), and IMPMC (Paris), with wide collaborative experience and complementary expertise, in the framework of the Réseau National de Recherche et Technologie du Stockage Electrochimique de l'Energie (RS2E) with prototyping platforms and strong industrial connection: www.energie-rs2e.com/fr .

The part of ICMCB www.icmcb-bordeaux.cnrs.fr/  (groupe « Energie-Matériaux et batteries » : www.icmcb-bordeaux.cnrs.fr/groupes/groupe2.html) deals more specifically with basic understanding of these LiMXO4F materials with related tavorite or triplite structures, as well as of the electrochemical processes occurring during lithiation/delithiation, via structural and spectroscopic characterizations.

The Ph-D project proposed deals with NMR characterization of these compounds, an important complement to macroscopic structural characterization from diffraction techniques, for local structure, redox phenomena and Li+ mobility. They indeed include several nuclei quite suitable for NMR (6,7Li, 19F, 31P, &). Being paramagnetic, their NMR signals are for the most part governed by hyperfine interactions (electron spin nuclear spin) that usually dominate other solid state NMR interactions. The (so-called Fermi) contact interaction will therefore mostly be exploited; it originates in the transfer of some electron spin density from the orbitals of the transition element to an s-type orbital of the atom studied by NMR. Understanding these mechanisms leads to a better understanding of the chemical bond, and a very detailed characterization of the local environment. Group 2 of ICMCB has pioneered such NMR characterization of paramagnetic materials for Li-ion batteries, a topic presently in very fast expansion.

The thesis work will be two-fold:

•         Measuring NMR spectra:

Due to the paramagnetic character, higher fields are not necessarily desirable. ICMCB owns two solid state NMR machines at 7T et 2.35 T (a quasi-unique one), with 35 MHz magic angle spinning probes, well suited to this work.

•         Modelling the spectra (assignment and analysis of mechanisms)

This will be based on analysis of the transferred electron spin density via ab-initio DFT calculations (VASP and Wien2k). These allow fisrt to assign the signals and second to understand the transfer mechanisms of the electron spins in an orbital-based spirit. This know-how was developed at ICMCB in particular via a 2009-1012 ANR project called LoCharATMO and a previous Ph-D work  (A. Castets, November 2011). There is presently a strong evolution of these methods in a highly competitive context.

The Candidate

The candidate must have a pronounced taste and ability for team work and for combination of experiment and theory. Good basic knowledge of solid state chemistry is required. Some knowledge of solid state NMR and possibly of DFT calculations is desirable.

Contact :

Michel Ménétrier : menetrier@icmcb-bordeaux.cnrs.fr +33 5 40 00 66 39

Dany Carlier : carlier@icmcb-bordeaux.cnrs.fr +33 5 40 00 35 69
Maître de conférences - Université Bordeaux1
33 +5 40 00 35 69

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