The Coatemo II project set out to develop a next‑generation lithium‑ion battery anode material composed of silicon and graphene. The goal was to produce a composite that combines high capacity, long cycle life, and economic viability. The work was carried out by a consortium of six partners: Graphit Kropfmühl GmbH (GK), FutureCarbon GmbH (FC), Dyneon GmbH (DY), InVerTec‑e.V. (IVT), Hochschule für Angewandte Wissenschaften Landshut (HAWL), and VARTA Microbattery GmbH (VARTA). Funding was provided by German research agencies, and the project ran over a multi‑year period, during which each partner contributed its specific expertise.

The technical core of the effort involved the synthesis of nano‑silicon (nSi) particles from monosilane (SiH₄) and their subsequent integration with reduced graphene oxide (rGO) to form a uniform composite. InVerTec’s reactor system, fed with high‑purity monosilane, carried out the gas‑phase decomposition of SiH₄ at temperatures above 300 °C. The reaction proceeds through a two‑step mechanism in which hydrogen is released and silicon atoms polymerise, ultimately yielding solid silicon nanoparticles. By varying the residence time, temperature, and SiH₄ concentration, the team was able to control the particle size distribution. Measurements showed that increasing the SiH₄ concentration within a limited range did not significantly alter the mean particle size, allowing for higher throughput without compromising quality. Scanning electron microscopy revealed that the synthesized particles formed agglomerates in the two‑micrometer range, similar to commercial silicon powders from Alfa Aesar and PlasmaChem. However, the primary particles were slightly smaller, which is advantageous for battery performance. Ultrasound treatment (30 s at 40 W) effectively dispersed these agglomerates, producing a stable colloidal suspension suitable for further processing.

Graphite Kropfmühl supplied graphite oxide, which was partially reduced at 100 °C during oxidation to ease downstream handling. The material then underwent a multi‑stage cleaning, drying, and re‑dispersion sequence. FutureCarbon produced the final dispersion of rGO and nSi, adding organic dispersants to increase solid loading without altering the intrinsic properties of the composite. The mixture was subjected to reactive spray drying at InVerTec, where a hot‑particle filter ensured that the resulting powder consisted of individually dispersed, reduced rGO‑coated silicon particles. This spray‑dried product was then plasma‑activated at GK, a step that further improves the electrical connectivity between silicon and graphene and enhances the composite’s electrochemical performance.

The resulting nSi/rGO composite exhibited a uniform distribution of silicon nanoparticles on graphene sheets, with reduced agglomeration and improved surface area. Energy‑dispersive X‑ray spectroscopy confirmed low residual oxygen content, a critical parameter for anode stability. While the report does not provide explicit capacity figures, the described process yields a material that is expected to deliver high specific capacity and excellent cycle life, meeting the project’s performance targets.

Throughout the project, the partners coordinated closely to align process decisions with the overall material goals. InVerTec led the silicon synthesis and analytical characterization, FC handled dispersion formulation, GK performed plasma activation, and VARTA supplied battery‑level testing. HAWL contributed to material testing and data analysis, ensuring that the composite met the stringent requirements for next‑generation lithium‑ion batteries. The collaborative framework enabled iterative optimization of each process step, culminating in a scalable production route for a high‑performance silicon‑graphene anode material.