Synthesis of LiFePO4/C cathode materials with both high-rate capability and high tap density for lithium-ion batteries

Abstract

LiFePO₄/C microspheres composed of many densely compact nanoplates were synthesized by a simple rheological phase method using nanoplate assembled quasi-microspheres of FePO₄·2H₂O as raw materials. The quasi-sphere FePO₄·2H₂O precursors were synthesized via a sodium dodecylsulfate assisted hydrothermal process. Both the LiFePO₄/C composite and the FePO₄·2H₂O precursors were characterized by XRD, TG, SEM, TEM, and Raman spectroscopy. The FePO₄·2H₂O quasi-spheres had a size distribution of about 1 μm and were composed of nanoplates with a 30 nm thickness. The LiFePO₄/C microspheres were also composed of the same sized nanoplates with an ∼2 nm thick amorphous carbon layer coating at the surface. The as-synthesized LiFePO₄/C composite showed excellent high-rate capability, with discharge capacities reaching 116, 96 and 75 mAh g⁻¹ at 10 C, 20 C and 30 C current rates, respectively. Furthermore, the LiFePO₄/C material composed of microspheres had a high tap density (1.4 g cm⁻³). Therefore, this LiFePO₄/C material can be the cathode material for large-scale applications such as electric vehicles and plug-in hybrid electric vehicles.