Abstract
Lithium iron phosphate is a promising cathode material for lithium-ion batteries owing to its safety, long cycle life, and environmental compatibility, but its performance strongly depends on the synthesis route. In this work, we report a custom-designed ultrasonic spray pyrolysis system equipped with a six-zone programmable furnace and a heated electrostatic precipitator for scalable and controlled LFP/C synthesis. Compared with conventional single-zone USP setups, this apparatus enables staged droplet-to-particle transformations, suppressing hollow morphologies and improving precursor uniformity. LFP/C powders synthesized in the 400-600 °C range exhibited poorly crystalline or partially amorphous structures as-sprayed, which transformed into phase-pure olivine LiFePO4 after annealing at 600 °C for 3 h under Ar. SEM revealed that spherical, submicron precursor particles (~200 nm ─ 1 µm) with smooth surfaces were produced directly by USP, while post-annealing preserved the morphology but introduced coarser textures and surface porosity. Such microstructural evolution is expected to balance tap density and Li⁺ transport pathways, consistent with prior studies of USP-derived LFP/C. Comparative analysis with two-phase nozzle and flame spray pyrolysis systems shows that the combination of gradient thermal control and electrostatic deposition in our setup improves the quality of the resulting powders and provides a promising combination of laboratory precision and potential scalability. These results demonstrate that the custom USP approach is an efficient and flexible platform for producing high-quality LFP/C cathode powders with controllable morphology and crystallinity.