Simultaneous rheology and impedance measurements on conductive colloidal suspensions

The development of renewable energy requires energy storage technologies, among which semi-solid redox flow batteries using conductive colloids are promising because of scalability. Understanding the flow and conductive properties of these colloidal suspensions is crucial in designing flow channels and optimizing operating conditions. However, the rheology and conductivity of colloidal suspensions are coupled and highly depend on the shear-induced structure, and these complex properties and the underlying microstructural origins are poorly understood due to a lack of appropriate instrumentation. To address this, we introduce a bespoke attachment to the stress-controlled (combined-motor-transducer) rotational rheometer which can measure rheology and electrical impedance under shear simultaneously. Using this rheo-impedance setup, we measure the thixotropy, anti-thixotropy, shear-dependent conductivity, and anisotropy of carbon black suspensions. We use the results to further propose a microstructure model to explain the measured bulk properties.