Meaning
Non-Newtonian materials whose dynamic viscosity decreases under increasing rate of shear stress represent a critical class of process chemicals in battery slurry coating. Manufacturing engineers utilize a shear thinning fluid to ensure that battery active materials flow easily through coating dies but remain stable when deposited. The behavior depends on the alignment of polymer chains and suspended particles along the flow lines.
This classification does not apply to simple low-molecular-weight solvents.
Flow Behavior
Resting slurry mixtures display high resistance to movement due to the random orientation of particles and binders. When treated as a shear thinning fluid, the material experiences a decrease in internal friction as the shear rate rises. This change allows the slurry to pass through slot-die gaps at high line speeds without requiring excessive pumping pressure.
Once the stress is removed, the viscosity rises to prevent runs.
Process Influence
The rate of viscosity recovery after coating dictates the final shape and thickness uniformity of the wet electrode layer. Utilizing a shear thinning fluid enables high-speed web coating while maintaining sharp edges on the foil strip. If the viscosity remains too low for too long, the wet slurry will sag and ruin the coating profile.
Accurate rheological profiles must be maintained.
Measurement Standard
Rotational viscometers equipped with variable speed spindles characterize the flow curves of the slurry. Quality laboratories measure the behavior of the shear thinning fluid across a wide range of shear rates to guarantee batch-to-batch consistency. Slurry batches with incorrect flow profiles are adjusted before the coating stage.
