  Carbon black particles act as electronically conductive additives in the
slurry electrodes used in electrochemical redox flow batteries. Stability and
dispersion of the carbon black particles in a slurry electrode are critical
parameters for its storage and the efficient functioning of the battery.
Modifying the carbon black slurry formulation with the addition of a nonionic
surfactant could potentially impart desired properties such as good particle
dispersion, gravitational stability and flowability imparting better
performance of the flow battery. Matching the typical slurry electrode
formulation, we dispersed carbon black particles in 1 M H$_2$SO$_4$ with volume
fraction $\phi$ = 0.01 to 0.06 and c$_{surf.}$ = 0, 0.05 and 0.1 M. Rheological
investigation reveals that the carbon black suspensions behave like colloidal
gels. Sedimentation kinetics of the process was measured by tracking the height
of the particle bed over time in a cuvette using a custom camera set-up. The
sedimentation dynamics here clearly resembled that of a gel collapse. At short
times we observe fast sedimentation associated with structural collapse of the
gel and at long times very slow sedimentation associated with compaction of the
sediment. Addition of a nonionic surfactant (Triton X-100) to the solvent above
CMC at $\alpha$ (= c$_{surf.}$/c$_{CB}$) $<$ 0.7 improves particle dispersion
and increases gel elasticity. However, for $\alpha >$ 0.7 leads to the
formation of a weaker gel that exhibits 'catastrophic collapse' under gravity
and has a lower viscosity.
