Linking of Model and Commercial Active Materials for Lithium Ion Batteries by In-situ Determination of Thermodynamic and Kinetic Data

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Essential requirements for the development of high-performance lithium ion batteries include the knowledge of kinetic limitations and of the thermodynamic stability. The systematic studies envisaged here are based on a new technique to determine temperature and enthalpy of phase transformations as function of composition of the active materials while the lithium content is controlled in-situ. Thereby, thin films deposited on piezoelectric transducers will be used which enables the simultaneous application of further methods such as X-ray diffraction and impedance spectroscopy. Microgravimetry and stable tracers with subsequent mass spectrometry will be applied to investigate the kinetics and the routes of the transport. Materials of interest include conventional oxides of the system Li(Co,Ni,M)O2 (M = Mn, Al) and new TiO2/Si and MoS2 compounds showing distinct microstructures due to preparation processes such as anodic oxidation. Based on the identification of the limiting transport step for lithium ions, modifications of the active surfaces or reduction of the diffusion lengths by tailoring the microstructure are intended. Further, the applicability of ionic liquids as electrolytes in combination with the above electrode materials will be investigated. The focus shall be mainly on systems with weakly coordinating anions.Those data and, in particular, the microstructure of the electrodes will form the basis to develop transport, defect chemical and thermodynamic models. Simultaneously, the data will be provided to the collaborators performing thermodynamic calculations.