Slot Die Coating Rheology in Battery Electrode Slurry Manufacturing
Slot die slurry throughput depends on high-shear thinning during extrusion and rapid low-shear yield stress recovery to prevent edge bead defects.
Active Material Sedimentation
Meaning
Industrial gravity-driven settling in multi-component slurry suspensions represents a critical phase-separation behavior during the storage and handling of battery electrode formulations. When battery slurry is held in storage tanks before coating, active material sedimentation describes the downward migration and accumulation of dense solid particles under gravity. This action leads to a non-uniform distribution of active particles and binders throughout the mixing vessel.
Such concentration gradients can compromise the consistency of the dry electrode.
Suspension Stability
The rate of particle separation depends on the balance between gravitational forces and viscous drag. In highly stable mixtures, polymeric additives create a network that suspends heavy particles for extended periods.
Separation Rate
Calculating the speed of settling utilizes Stokes law, where the terminal velocity is proportional to the square of particle radius and the density difference between phases. However, in concentrated battery slurries, particles do not settle independently. Instead, they interact with each other and with polymer chains, creating hindered settling behaviors that deviate from the single-particle model.
This collective movement can cause a sharp interface to form between the clear supernatant liquid and the concentrated sediment below, a process that varies with solid loading and slurry temperature.
Precipitation Outcome
Once sedimentation completes, the resulting dense cake at the bottom of the container is difficult to redisperse. This hard-packed sediment blocks pump inlets and causes variations in the slurry delivered to the coating head.