Non-equilibrium gel formation in suspensions of conductive particles in electric field

In flow batteries, incorporating very small (~20 nm) conductive particles, such as carbon black, into a battery slurry can enhance the charge transport while triggering a depletion-attraction interaction among larger (~1 micron) active particles inside a slurry solution. To investigate this effect, we utilize large-scale numerical simulations to study the behavior of suspensions of ideally conductive particles in an electric field with an attractive potential energy. These suspensions are known to undergo two nonlinear electrokinetics, namely induced-charge electrophoresis (ICEP) and dielectrophoresis (DEP), where ICEP is predominant over DEP for ideally conductive particles. A gel state is determined based on the average number of interparticle bonds. At low field strengths, a non-equilibrium gel is formed due to strong attractive interactions. As the field strength increases, the gel begins to break and reform while maintaining gel states as its average bond number remains almost the same. At sufficiently high field strengths, the electrokinetic effects become dominant to disrupt the bond formation, which is no longer in a gel state. A phase diagram for a universal gel line in terms of the field strength and volume fraction is drawn and compared to colloidal gels.