Lattice structure, Li-dynamics and ordering phenomena in single crystalline model systems for Li-ion batteries: NMR, x-ray diffraction, and theoretical studies

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This project addresses the complex relationship between Li-kinetics, ordering phenomena, structure and electrochemical behavior of Li-ion battery materials. Single crystalline model compounds will be studied by means of Nuclear Magnetic Resonance (NMR), x-ray diffraction as well as theoretical modelling. We will combine the two complementary experimental probes on the same samples in order to arrive at a comprehensive understanding of possible Li-ordering and its impact on the Li mobility in Li battery materials. The use of single crystals enables to study Li-ordering in detail, especially by single crystal diffraction experiments using high-energy synchrotron radiation. Besides, single crystals can be treated electrochemically along different crystal axes involving different Li diffusion mechanisms that have an impact on the crystal structure. The melting of Li-ordering and the following Li-ion dynamics will be traced by x-ray diffraction and in particular NMR, which is a powerful tool for probing dynamic properties of Li materials. In operando studies are planed for both techniques. Crystal structures and superstructures of charge and/or spin ordering will be studied by high precision total energy calculations on the basis of LSDA, GGA and LSDA+U density functionals. Moreover, adiabatic potential surfaces for the motion of Li ions will be studied by carefully relaxing the structures using forces on the basis of the above mentioned density functionals.