2022 Annual Meeting
Quantifying Rheological and Electrical Behavior of Semi-Solid Flow Battery Carbon Slurries
Solar and wind renewable energy sources have become competitive options compared to fossil fuels but new innovations of grid-scale energy storage systems are needed to implement them into common use. Semi-solid flow batteries (SSFBs), batteries composed of a slurry active material, are one possible solution due to the decoupling of the battery energy capacity and power density. Conductive carbon black has high potential as an active material due to its low capital and high surface area for optimizing capacitance. Both the rheological and electrical responses of conductive carbon black slurries have been characterized independently, but there have seldom been reports on the two measurements in tandem. To this end, this research is focused on creating a custom-built electrochemical cell capable of performing electrical measurements while a slurry sample is being sheared. The electrochemical cell - built using 3D printing - attaches onto a DHR rheometer, allowing electrical measurements from a VersaSTAT potentiostat to travel through the rheometer. Reproducible rheological data was generated utilizing a solvent trap to minimize evaporation and a pre-experiment procedure used to erase the sample shear history. The capacitance of a carbon black slurry in 35 mg/ml NaCl solution under shear between 0 to 1250 1/s shear rate was calculated utilizing equivalent circuit modeling of Nyquist plots obtained from electrical impedance spectroscopy (EIS). There are two important results of this research. First, it is demonstrated that - with some innovative engineering - simultaneous rheological and electrical measurements can be done on the DHR rheometer. Second, the capacitance results showed an increase in capacitance as shear rate increased, which is inline with previous assumptions about carbon black slurry aggregation behavior. Consequently, high shear rates are necessary for reasonable capacitance to be achieved within SSFB, influencing future design parameters for SSFBs.