(585b) Characterizing the Influence of Surfactant Adsorption on the Electrical Properties of Flowing Carbon Black Slurries Important to Flow Battery Applications

Designing the formulation of carbon black slurry plays an important role in optimizing a flow battery's performance, influencing both its conductivity, capacity, and the prevention of sedimentation during storage. Sedimentation and adsorption studies have shown that at high nonionic surfactant concentrations (Triton X-100) where α (c_surf./c_CB) > 0.7, surfactants adsorb to the carbon black and saturate the surface, leading to an unstable slurry. To test how this attributes to the battery performance, conductivity and capacity of the slurry flowing through the battery cell were measured via cyclic voltammetry at varying scan rates from 1mV/s to 1V/s and flowrates from 0 – 170ml/min. Matching the typical flow battery slurry formulation, we suspended carbon black in 1M H₂SO₄ and 0.55M ZnSO₄ with carbon black loading ranging from 1-8 vol% and nonionic surfactant concentration, α ranging from 0-0.7. Results show that at lower flowrates and scan rates, the capacity is higher due to longer residence time of particles in the battery cell. However, conductivity is higher at faster flowrates and the effect of the flowrate dominate over scan rate, especially at high flowrates. With addition of surfactants, both conductivity and capacity decrease with increasing α until at α = 0.7 in which the both are completely lost. We attribute this to carbon black particles losing its conductivity as surfactants that are adsorbed to the surface disrupt the electrical percolated network and particles can no longer electrically contribute in the slurry.