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Project leader: Prof. Dr. Harald Schmidt
Funding period: 06/2016 - 12/2020
Funding body: German Research Foundation
The topic of this application is the first systematic investigation of Li tracer diffusion in the lithium-silicon (LixSi) system. On the one hand, this is relevant for a fundamental understanding of kinetic processes at negative electrodes in lithium-ion batteries for optimized charging times, power density and maximum capacity. On the other hand, there is interest in the further development of a methodology that is rarely used in the field of Li diffusion using an interesting model system.
The experiments are to be carried out on LixSi compounds as a function of the Li content x, the temperature and the annealing time. For this purpose, different model systems in the form of 6LixSi/7LixSi isotope heterostructures are used, which are deposited on Si wafer substrates with ion beam sputter deposition. Comparative studies on electrochemically lithiated silicon layers will complement the experiments and highlight the differences. Secondary ion mass spectrometry in depth profile mode and in lens scan mode will be used for isotope-selective analysis. This allows the determination of diffusion coefficients in the range of 10-10 to 10-23 m2/s. If the diffusion coefficients follow the Arrhenius law, the activation enthalpy of diffusion is determined and analyzed with regard to possible diffusion mechanisms in the context of theoretical literature studies. The results will be compared with electrochemical GITT measurements.