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CFP2022-1108

A mechanical synthesis route for the production of silicon graphite composites for lithium – ion – batteries
Poster Exhibition
Production processes
Design

In order to fulfill the rising demands of electronic devices and automotive applications, increasing the energy density of Lithium-Ion-batteries (LIBs) is of great importance. Commonly, graphite is used as anode active material, because of its high reversibility for Li+ inter – and deintercalation, resulting in a good cycle stability. However, as graphite is limited by its low theoretical gravimetric specific capacity new active material systems are needed. One promising anode active material for LIBs is silicon. It provides a theoretical specific capacity about ten times higher then commonly used graphite. However, silicon-containing anodes are undergoing high volumetric expansion, up to 300 % during the insertion of Lithium-ions, leading to pulverization of particles and a continuous growth of the solid electrolyte interface layer. Furthermore, silicon has a poor electrical conductivity [4]. Therefore, many approaches exist in combining silicon (Si) and graphite (C) as a composite material to increase the energy density of LIBs. Typical synthesis routes are for example chemical vapour deposition, thermal decomposition, spray drying and mechanical milling. An alternative manufacturing route is the high-intensity mixing process, which has received little attention so far. High-intensity mixers offer the advantage of a cost-efficient synthesis route and are well scale-able.
Hence, a mechanical granulation process route for Si/C composites in a high intensity mixer is evaluated. The produced Si/C composites consist of micron-sized flake graphite particles (x50 ≈ 5,5 µm) and nano-sized silicon particles (x50 < 150 nm). The nano-silicon particles were dispersed in ethanol and added to the agitated graphite powder bed, while parameters like dosing time and rotational speed were varied. Ethanol acts as a liquid binder, that evaporates during the granulation process. The dried and sieved materials were characterized on powder level (granule stability/strength, particle size distribution, specific surface area, silicon content). The particle size was found to be dependent on both the rotational speed and the liquid dosing time. The produced composite particles prove to be stable even without the use of an additional polymer binder and were further processed into a suspension and coated on a current collector. The electrochemical performance was determined in full cells.

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Co-Autoren

Peter Michalowski, Arno Kwade

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