(280d) Powder Characterization for Electrode Production Improvement

Electrode production is a critical step, determining the battery properties such as the power density, specific capacity, and longevity. Special care is consequently paid to electrode manufacturing. At the start of production, raw materials, made of active material, conductive additive, and binder, are generally dry-mixed in powder form and then added to a solvent to make a slurry. This slurry is spread on a current collector to create an electrode. In addition, new dry processes are more and more preferred for ecological and financial reasons, directly handling raw materials in dry powder form. Therefore, powder characterization becomes more and more important for electrode manufacturing improvement.

A critical required property for batteries is energy density. The larger the specific and areal capacity, the more energy per unit of weight and volume the battery can store. Batteries based on sulfur as an active material for cathode are more and more considered. However, while sulfur has a high theoretical specific capacity, its poor conductivity makes it unable to exchange electrons during the electric charge. In addition, the poor flowability of sulfur makes it challenging to handle during electrode manufacturing processes. For these reasons, carbon black is generally dry mixed with sulfur powder to improve conductivity and flowability.

Composite powders made of sulfur and carbon black are also envisaged for improving the conductivity and the energy density of the blend. Nevertheless, composite sulfur/carbon black powders give different behaviour compared to blends prepared by dry-mixing. In this work, we analyzed blends made of sulfur and carbon black prepared by dry-mixing and in composite form. The composite powder was prepared by melting the sulfur and mixing it with the porous medium made by the carbon black and then milling the composite material. For the different powders, the bulk density and packing dynamics were measured with a new and improved tapped density method (GranuPack, Granutools, Belgium) and flowability with a rotating drum method (GranuDrum, Granutools, Belgium). An increase in capacity of the produced batteries was observed to be correlated with an increase in bulk density for the composite mixing method compared to the dry-mixing method. In addition, different powder flowabilities were observed between composite and dry-mixed powder, highlighting the importance of characterizing powder properties for electrode manufacturing improvement.