Porous supraparticles of lifepo₄ nanorods with carbon for high rate li-ion batteries

Porous supraparticles, or spherical aggregate of LiFePO4 with carbon were prepared by spray-drying of LiFePO4 nanorods and glucose by heat treatment. Rod-like LiFePO4 nanoparticles are prepared by a solvothermal process, which was then sprayed with glucose as a carbon source forming spherical particles of LiFePO4 nanoparticles and glucose. Through the heat treatment under a nitrogen atmosphere, glucose was carbonized⁴ inside LiFePO₄ supraparticles. Due to the interstices between nanoparticles, the spherical aggregates showed fairly high specific surface area (35.0104 m² g⁻¹). Supraparticles-based electrode exhibited high initial capacity as well as remarkably high rate capability; discharging capacity was 146.15 mAhg⁻¹ at high 10 C (1602.5 mA/g) and 126.58 mAhg⁻¹ at 50 C (8012.5 mA/g). Moreover, cyclic performance at 5 C (801.25 mA/g) was relatively high as well (99% retention after 100 times test). Our porous carbonized LiFePO₄ supraparticles have higher packing density or tap density (1.07 g/cm³) than carbonized LiFePO₄ nanoparticle (0.78 g/cm³), which is considered an important factor in the practical application.