Case Study: SpeedMixer Application for Electrode Slurry Mix
Dry Blending and Grinding
Dry blending, with or without grinding media, of active materials with conductive additives and/or graphite for improved dispersion in composite slurry and enhanced electrical conductivity – particularly useful with nano-sized actives
Dry mixing of powders without grinding media to break up clumps for improved incorporation into slurry and dispersion – “gentle” technique, helpful when primary particle damage should be avoided
Grinding with ZrO beads or other media to break up stubborn agglomerates and/or reduce primary particle size
Degassing of Viscous Solutions
For most solutions, 2 min at 2000 RPM in Speedmixer (no vacuum) eliminates air bubbles more quickly and effectively than vacuum cycling without centrifugal mixing
Applying vacuum while mixing with Speedmixer degasses more stubborn solutions
Slurry Preparation – Incremental Dilution Method
Prepare at high solids content to create a uniform paste, incrementally dilute with solvent to achieve favorable rheological properties
Generally faster and often better dispersion than slurry preparation with overhead mixer
No issues with entrained air
Usually results in higher solids mass fraction than overhead mix, while maintaining “coatable” viscosity
Improved slurry yield compared with overhead mixing – no mixing blade related losses, reduced slurry adhesion to vessel walls compared with glass beaker
Slurry Preparation with High Surface Area Materials
Improved rheological properties with high surface area materials, e.g. bimodal graphite for fast charge applications
Reproducible shear-thinning properties observed in Speedmixer prepared slurry
Oddly low viscosity at low shear rates for Overhead mixed slurry, with shear-thickening above 1 s-1 – this can cause serious problems with scale-up > attributed to entrained air that could not be removed via vacuum degassing
