Abstract Summary (Max 250 words)
Understanding of dry mixing in the manufacturing of lithium-ion battery electrodes has the potential to improve process sustainability by either reduction or elimination of organic solvents and consequent energy costs of slurry drying. The dry mixing dynamics of NMC 622, a cathode electrode material used in lithium-ion batteries, were simulated using the Discrete Element Method (DEM), with the simulations calibrated from the material properties of NMC 622. These simulations were then validated using experimental Positron Emission Particle Tracking (PEPT) data across a range of rotor tip-speeds at a fixed co-rotating pan speed and fill height. Both methods captured a disengagement of the free surface of the electrode material from the rotor at higher tip-speeds, and diminishing mixing performance, confirmed by estimating the transient mixing time using the Lacey mixing index. The DEM simulations were used to explore the granular dynamics of NMC 622 at different fill heights. Fill height was adjusted by adding more particles into the mixer up to 2.5 times the initial number of particles. It was found that this increased the volume of the granular fluid around the rotor and lowered the number of particles in the granular gas above, as less are thrown clear of the main material flow by the rotor. Particle velocities, changes in vessel circulation time, dispersion and Péclet number were calculated. These gave an understanding of the dominant mixing mechanism and vessel turnover; the Lacey mixing index was calculated to compare transient mixing times and particle dynamics in the granular fluid.
