Self-Assembled 3-D Cage-like Hierarchical LiFePO_4 Architectures and Their Application as a Cathode Material in Lithium-Ion Batteries

摘要

Self-assembled 3-D cage-like LiFePO_4 with monodisperse structure from nanoparticles have been synthesized by co-solvent of ethylene glycol (EG) and water hydrothermal route using Li_2SO_4, Fe(NO_3)_3?9H_2O and P_2O_5 as raw materials. Nitrogen adsorption-desorption measurement suggests that mesopores and macropores exist in these hierarchical microarchitectures. The formation process of the 3-D cage-like LiFePO_4 microspheres has been investigated in detail. It was found that EG not only played multifold roles in the formation process of such unique LiFePO_4 hierarchical microstructures, but also acted reductant in the hydrothermal synthesis. In addition, employing P_2O_5 instead of other phosphorus sources was necessary for the formation of such unique microstructures. The possible formation mechanism for the LiFePO_4 hierarchical microstructures have been presented in detail. As the cathode material for lithium batteries, the as-prepared LiFePO_4/C composite exhibits excellent cycle stability (158 mAh g~(-1) at 0.1 C up to 300 cycles) and good rate capacity (120 mAhg~(-1), 10 C).