2024 AIChE Annual Meeting
Influence of Surfactants on Electrode Slurries Used for Flow Battery Application
Flow batteries are an emerging technology used for energy storage on the grid-scale level. The performance of a flow battery greatly depends on the efficiency of the internal slurry electrode, which affects the conductivity, capacity, and stability of the slurry during inactive periods. To improve on slurry stability, surfactants have been added into the carbon black slurry electrode. Previously, one non-ionic surfactant, Triton-X 100, has shown a relationship between concentration of surfactant and slurry stability. It was shown that surfactant concentration affected slurry stability at a critical mass ratio of surfactant to carbon black (α =csurf/ccb) which for Triton-X 100 was 0.7. At this point, the surface area of the carbon black particles are saturated with surfactants which inhibit the interparticle interactions, leading to an unstable slurry. This study was extended with two more surfactants, Triton-X 45 and Triton-X 405, to investigate the relationship between surfactant molecular weight and slurry stability. The adsorption studies concerned finding critical α for both Triton-X 45 and 405. Adsorption studies were completed using UV-Vis spectroscopy for α values ranging from 0 – 1.5. Results show that there is no significant difference in critical α between Triton-X 100, Triton X-45, Triton X-405, showing that the molecular weight of surfactant does not affect surfactant saturation at a CB particle surface. In addition, sedimentation studies have been conducted in order to measure the settling behavior of carbon black particles with the addition of surfactants. Previous studies have demonstrated that carbon black slurries behave like a colloidal gel interparticle attraction, but collapse under gravitational stress, leading to phase separation. The sedimentation behavior of gels can be influenced by various factors such as particle concentration, gel strength/elasticity, and the presence of surfactants. Thus, as was done previously with Triton-X 100, sedimentation experiments with Triton-X 45 and Triton-X 405 were conducted. This is crucial to understanding how concentration of surfactant and surfactant size affects gel collapse behavior over time. Time studies are ongoing for various carbon black weight percentages and α values.