Thermodynamics and kinetics of lithiation and delithiation of high capacity anode materials at elevated temperatures

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Temperature management is a costly and energy consuming necessity in today’s Liion batteries. The majority of organic solvent and gel based electrolytes in Li-ion batteries is instable above 60°C and carries an inh erent risk for disaster, which has to be reduced by additional technological features.The most promising high capacity anode materials like silicon and tin outperform graphite by a factor of 10 in capacity, but show rater poor reversibility of the lithiation and delithiation process. A smooth and uniform lithiation and delithiation is hindered by unfortunate thermodynamics and kinetic limitations.In close cooperation with the theory-oriented workgroups Prof. Schmid-Fetzer (Clausthal Zellerfeld), Prof. Rettenmayr (Jena), Prof. Song (Beijing) and through them also with Neugebauer (Düsseldorf), we aim to develop a Li-ion battery system, which will use lithiation and delithiation of high capacity anode materials at elevated temperatures (60°C-200°C). Thus, by variation of te mperature and material structure and composition, we will be able to investigate the yet not understood phase changes during the lithiation process with two essential methods: 1. by NMR, which is currently the only method to detect changes in the local environment of lithium in bulk materials. 2. by atomic probe analysis to allow detection of the composition of these materials with atomic resolution. On this base, thermodynamic and kinetic models will be built, to shed light on phase changes during lithiation and delithiation. Our final goal is to use the predictions, derived from the reality checked kinetic and thermodynamic modeling, to develop a high capacity anode material without the current limitations on reversibility. In the far end, we will reach a battery system that can be reliably used at elevated temperatures and would not rely on a complex temperature management system used in today’s batteries for electro mobility applications.