Electrochemical and microstructural analysis of the processes occurring in Si microwire-array anodes (and full-cells) for high capacity Lithium ion batteries

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The main goal described in the first period proposal was: To build the most advanced silicon wire anode (SWA) for Li ion batteries presently existing even with higher capacities and higher reliability, more reliable by obtaining a better understanding of the basic processes occurring during lithiation / delithiation. Even though this is a challenging goal, it could be already fulfilled for the most part, so that in the here proposed continuation the goal will be pushed forward, mainly towards in depth understanding of the properties at performance limits and advanced full cell performance. Throughout the first period, the size dependency on the (peak) potential was understood. With FFT-Impedance Spectroscopy it could be understood how the different lengths and the thicknesses of the wires influence the charge transfer and the elastic interaction within the anode. Voltammetric measurements showed how the diffusion is limited when using different wire geometries. Those packages are still scheduled in the third year to estimate the property change at performance limits like temperature influence and different cycling parameters. This resulting structural change should be investigated by transmission electron microscopy (TEM) in the following third year. A simple and reliable method for the transfer of moisture sensitive Li-Si was successful and might boost the scientific relevance of electron microscopy in the field of moisture and beam sensitive samples. Besides the continuation of the work packages as planed in the initial proposal, we introduced an additional work package (WP 9) dealing with TEM analyses on potential cathode materials.