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.

中文翻译：

---

表面活性剂导致液流电池应用中炭黑悬浮液的灾难性坍塌

炭黑颗粒在电化学氧化还原液流电池中使用的浆液电极中充当导电添加剂。炭黑颗粒在浆料电极中的稳定性和分散性是其储存和电池有效运行的关键参数。通过添加非离子表面活性剂来改性炭黑浆料配方可能会赋予所需的性能，例如良好的粒子分散性、重力稳定性和流动性，从而赋予液流电池更好的性能。匹配典型的浆料电极配方，我们将炭黑颗粒分散在 1 MH$_2$SO$_4$ 中，体积分数 $\phi$ = 0.01 到 0.06 和 c$_{surf.}$ = 0、0.05 和 0.1 M。流变学研究表明，炭黑悬浮液表现得像胶体凝胶。该过程的沉降动力学通过使用定制相机设置在比色皿中随时间跟踪颗粒床的高度来测量。这里的沉降动力学显然类似于凝胶塌陷。在短时间内，我们观察到与凝胶结构坍塌相关的快速沉降，而在长时间内，我们观察到与沉积物压实相关的非常缓慢的沉降。在 $\alpha$ (= c$_{surf.}$/c$_{CB}$) $<$ 0.7 时向 CMC 上方的溶剂中添加非离子表面活性剂 (Triton X-100) 可改善颗粒分散并增加凝胶弹性。然而，$\alpha >$ 0.7 会导致形成较弱的凝胶，在重力作用下表现出“灾难性塌陷”并具有较低的粘度。