Hetero-aggregation of colloidal silica and carbon black in flames

Project Leader:

Prof. Dr.-Ing. Frank Rhein
Karlsruhe Institute of Technology (KIT)

Nanoparticles are widely used in industrial products because they combine material inherent physio-chemical properties with high surface to volume ratios. These properties are multiplied and complemented by the functional mixing with other nanoparticle species. Subsequently, hetero-contacts are formed at the distinct interface of the two materials, which are of fundamental importance for the desired functional properties of the mixture. This project focuses on the development of tailor made hetero-aggregates for battery applications. Within batteries, a blend of multiple components, including active materials, polymer binders and carbon black, ensures efficient energy storage. Therein, the creation of electrical pathways between the usually non-conductive active material particles is achieved by the addition and homogenous dispersion of carbon black within the electrodes. However, deformation and breakage of carbon black during manufacturing degrades the final conductivity of the battery. Hence, this project aims at improving the stability of carbon black by hetero-aggregation with silica in spray flames.

The characterization of the hetero-contact and the resulting mixing quality of the hetero-aggregates is still a major challenge. Therefore, the development of an extensive image analysis of the mixing quality in combination with multi-scale particle analysis is pursued. The combination of both methods provides comprehensive information on all relevant length scales, leading to an understanding of the interaction between mixing quality and aggregate properties.  This understanding is crucial to subsequently determine sophisticated metrics like the mixing quality directly from straight-forward measurements without the need of time-consuming TEM-analysis. Furthermore, this knowledge about the mixing quality depicts a major milestone towards the direct characterization of the hetero-contact itself via small angle X-ray scattering (SAXS). Subsequently, material functions of relevance to the manufacturing process of batteries and the electro-chemical performance are studied with respect to the hetero-contact and process conditions. As a consequence, the corresponding research areas “preparation and formulation of hetero-aggregates” and “characterization of hetero-contacts and aggregates and their material function” are covered. In conclusion, the comprehensive insight into the quantity and quality of the hetero-contacts bridges the gap from aggregate properties to functional properties and the resulting material functions.