Résumé
1. AbstractHigh-resolution Magic Angle Spinning NMR can be performed on a wide variety of materials and providea wide range information on many atoms such as 6Li, 7Li or 23Na and correlation or relaxation experimentscan provide information on the localization of lithium or sodium ions and eventually probe phase separationin battery materials. [1,2]Moreover, in favorable systems such as lithium titanates, it has been shown that surface fluorination withXeF2 greatly improves the electrochemical properties. In such systems, high resolution MAS-NMR at highmagnetic field can help quantify the amount of fluorine in the structure, and the 19F chemical shift analysisyields information on the fluorine environment. Moreover, spin counting strategies based on HeteronuclearMultiple-Quantum Correlation experiments can provide the number of fluorine atoms which are coordinatedto lithium ions and help understand what kind of structures are created locally upon fluorination.[3]2. ExperimentalMost experiments on paramagnetic samples were realized at moderate magnetic field (4.7 T or 200 MHzfor 1H) with 1.3 mm rotor spinning around 60 kHz under N2 in Bruker spectrometers. For diamagneticsamples such as LTO, high magnetic fields (20 T or 850 MHz for 1H) provided a better signal-to-noise ratioand allowed spin counting experiments to be performed in 1.3 mm rotors.[1] B.Li, G.Rousse, L.Zhang, M.Avdeev, M.Deschamps, A.M.Abakumov, J.-M.Tarascon,Constructing “Li-rich Ni-rich” oxide cathodes for high-energy-density Li-ion batteriesEnergy Env. Sci. 16, 1210-1222 (2023)[2] Q.Wang, S.Mariyappan, G.Rousse, A.V.Morozov, B.Porcheron, A.Iadecola, R.Dedryvère, J.Wu, W.Yang,L.Zhang, M.Chakir, M.Deschamps, M.-L.Doublet, A.M.Abakumov, J.-M.TarasconUnlocking anionic redox activity in O3-type sodium 3d layered oxides via Li substitutionNat. Mater. 20, 353–361 (2021)[3] Y.Charles-Blin, D.Flahaut, J.B.Ledeuil, K.Guérin, M.Dubois, M.Deschamps, A.M.Perbost,L.Monconduit, H.Martinez, N.LouvainAtomic Layer Fluorination of the Li4Ti5O12 Surface: A Multiprobing SurveyACS Appl. Energy Mater. 2(9), 6681-6692 (2019)