(463b) Surfactant-Driven Dynamic Changes in Rheology of Activated Carbon Slurry Electrodes

Advancing the manufacturing, operation, and performance of redox flow batteries based on carbon black slurry requires a deep understanding of how formulation impacts its rheological profile and ultimately battery performance. This presentation will summarize our work measuring the linear and nonlinear rheological response of activated carbon (AC) based slurry electrode materials in the presence of a Triton X-100, which is a non-ionic surfactant commonly employed in these applications. Results showed the slurry behaved as a colloidal gel with elasticity remaining constant despite increasing surfactant concentration until a critical surfactant concentration (Csurf/Cac ~ 0.65), above which the slurry abruptly transitions to a fluid with no measurable yield stress. This critical surfactant concentration at which the rheological profile undergoes a dynamic change matches the concentration found previously for gel collapse of this system. Moreover, this transition is accompanied by a complete loss of electrical conductivity. These data show that site specific adsorption of surfactant molecules often used in slurry formulation have a significant and dramatic impact on flow behavior, which should be considered when formulating a slurry electrode.