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

Abstract

Removing solvents from nanoparticle solid suspensions requires the same diligence as drying pharmaceutical ingredients. LiFePO 4 nanoparticles suspension in water oxidize, sinter, and Li 3 PO 4 segregates on the surface when they dry in a furnace. Spray drying preserves the material properties because contact times are on the orders of seconds; furthermore, the atomized droplets ensure particles are small (5 m to 20 m) and dispersed. A Yamato GA-32 (120 mm inner diameter) spray dried in co-current flow a nanoparticle suspension of LiFePO 4 in water, with a solid content up to 60 %. Atomization gas velocities of 140 m s −1 to 350 m s −1 agglomerated the nanomaterial into spherical particles that ranged from 3 m to 10 m. The particle diameters ranged from 10 m to 20 m at atomization velocities of 50 m s −1 to 140 m s −1 . At this condition, yield was lower because the semi-dried particles adhere on the wall. At 150 • C to 200 • C the surface area reached 26 m 2 g −1 while from 50 • C to 100 • C it varied from 14 m 2 g −1 to 20 m 2 g −1 . The trend for mesoporosity versus spray drying temperature is the same as for surface area: pore volumes are higher (0.18 cm 3 g −1 ) above 200 • C and 20 % lower below 200 • C. Drying temperature modifies drying speed; low temperatures compact the powders more than high temperature which results in lower surface area and porosity. Figure 13. Theta-2-theta acquisition at 50 kV and 40 mA, using a Cu anode, Gonio mode, CuK˛sideband removed.

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