Controlled Particle Size Distribution in Ultrasound-Assisted Lithium Carbonate Precipitation

This study investigates ultrasound-assisted precipitation (sonocrystallization) as a method to precisely control lithium carbonate (Li₂CO₃) particle formation from a lithium-rich solution of spent lithium-ion batteries. In addition to its high purity, to meet battery-grade standards, the Li₂CO₃ precipitates must exhibit well-defined particle size distribution. By controlling the nucleation and growth rates through the simultaneous adjustment of ultrasound power and temperature, both the particle size and morphology of the precipitates can be accurately defined. A detailed kinetic analysis was performed to evaluate the effects of ultrasound power and temperature on the precipitation process. The proposed kinetic model combining population balance and a compartment-based discretization approach accurately simulated the particle size distribution. The model provided general kinetic parameters for nucleation and particle growth as functions of the process variables. Experimental validation showed that increased ultrasound power reduced the particle size and improved uniformity, while lower temperatures promoted smaller particles due to the distinct crystallization behavior of the endothermic process. Compared to conventional stirring precipitation, which results in larger agglomerated morphologies, the ultrasound-assisted precipitation yielded non-agglomerated particles. Under the optimal condition (320 W, 90 °C), the process achieved particle sizes of <i>d</i> ₁₀ = 2.85 μm, <i>d</i> ₅₀ = 5.5 μm, and <i>d</i> ₉₀ = 14.55 μm, meeting industrial specifications. These experimental and kinetic simulation findings provide general insight into controlling the particle size through sonocrystallization, particularly to support scalable battery-grade Li₂CO₃ recovery from secondary sources.