Shear-driven viscosity enhancement in battery slurry

The lithium-ion battery electrode manufacturing process requires a thorough understanding of the rheology of complex and dense non-Brownian slurries. This study investigates shear-induced viscosity enhancement observed in aqueous graphite slurries, which serve as a simplified model for battery anode slurry. In these slurries, the viscosity increase under shear becomes more pronounced at higher graphite concentrations. This behavior is also accompanied by antithixotropy, where viscosity increases over time under shear flow. Flow reversal tests suggest that viscosity enhancement—driven by both the shear rate and shearing time—is attributed to a frictional contact network. The contact stress increases with shear rate or shearing time, while noncontact stress remains constant. Interestingly, the network appears to remain partially even after the cessation of flow, as evidenced by residual stress and a dramatic increase in the storage modulus. The persistence of the contact network could be attributed to hydrophobic interactions that restrict the relaxation of the particles. Our findings offer a deeper understanding of the contact-driven thickening behavior in attractive non-Brownian suspensions, providing insights that could be applied to optimizing industrial processes.