Laminar-flow Broadband Electrochemical Impedance Spectroscopy of Shear-Dependent Dispersion Changes in Carbon Black Slurries

The shear-dependent evolution of electrically active networks in carbon black (CB) electrode slurries remains insufficiently resolved under processing-relevant flow conditions, limiting rational slurry design for scalable battery manufacturing. Here, we apply continuous-flow broadband electrochemical impedance spectroscopy (EIS, 7 MHz-10 mHz) using a custom laminar flow cell to investigate acetylene black slurries (0.3–5.0 wt% CB in PVDF/NMP) under static and flowing conditions up to 50 mL min−1. Under no-flow conditions, the impedance spectra evolve systematically with CB loading and exhibit a connectivity transition near 3.2 wt% CB, above which an additional high-frequency response becomes spectrally resolvable. The spectra were analyzed using hierarchical R||CPE models, and CPE-derived effective capacitance-like parameters were used to describe the frequency-resolved redistribution of electrically active processes. These analyses show that the composition near the connectivity transition is the most sensitive to flow: at 3.2 wt% CB, lower flow conditions within the laminar regime shift the response from fast to intermediate relaxation contributions, whereas higher flow conditions within the laminar regime suppresses the distinct high-frequency contribution entirely. In contrast, the 5.0 wt% slurry shows comparatively limited spectral redistribution, consistent with a more robust and redundant conductive network. Together, these results establish laminar-flow broadband EIS as a process-relevant approach for diagnosing flow-induced reorganization of electrically active slurry networks under pressure-driven, coating-relevant hydrodynamic conditions.