Ultrasound assisted wet stirred media mill of high concentration LiFePO₄ and catalysts

Abstract

Wet media mills grind solids to the nanometric size and the performance of the mills depends on solids loading, particle morphology, surfactant concentration, and material characteristics. As the particle size decreases, they tend to form clusters that reduce the grinding efficiency. Ultrasound deagglomerates these clusters thereby increasing efficiency but, surprisingly, it can operate at higher solids concentrations. We processed suspensions of LiFePO 4 (LFP) with a yttria stabilized zirconia media with a size from 0.3 mm to 0.4 mm, and surfactant-to-LFP mass ratio 0.008. The combined method ground the particle size from 35 m down to 0.2 m in 90 min with a throughput of 0.68 kg LFP /kg media /h. We also tested the improved wet media milling on two catalysts: (WO 3 /TiO 2 and vanadyl pyrophosphate (VPP) precursor) to confirm the trends. We adopt a model for the steady state and repeatable micronizing process with ultrasonic assistance. According to TEM imaging the WO 3 /TiO 2 catalyst primary particles (20 nm) are much smaller than the agglomerated ones measured by laser diffraction (470 nm). VPP precursor slurry is normally an unstable suspension that is hard to mill. It formed agglomerates with recrystallized silica and VPP flocculation. The ultrasound-assisted wet milling technique produced nanometer scale particles (180 nm), which is otherwise impossible. We developed and updated the steady state micronizing process with ultrasonic assistance using a simplified population balance model. The model accounts for R 2 > 0.95 of the variance in the experimental data.

Morphological changes of vanadyl pyrophosphate due to thermal excursions

“…An LA-950 Horiba laser diffraction analyzer measured the particle size distribution (PSD) based on the Mie theory (Table 5.2) [117] . An AUTOSORB-1 (Quantachrome Instruments, USA) measured the surface area of the powder samples by the standard multi-point Brunauer-Emmett-Teller (BET).…”

Flame‐assisted spray pyrolysis of lithium and manganese precursors to polycrystalline LiMn2O4

“…In sample F9, we added 0.4 % tween‐20 (Aldrich) as a stabilizing agent. This organic surfactant does not contaminate LMO because it evaporates or decomposes to carbon above 100 C …”

Influence of atomization conditions on spray drying lithium iron phosphate nanoparticle suspensions

“…The grinding chamber rotated at 60 Hz and a pump recirculated the mixture at 360 mL min. Within 30 min of milling, the primary particle size distribution median reached 200 nm …”