Thermal explosion synthesis of LiFePO4 as a cathode material for lithium ion batteries

Abstract

Olivine-type LiFePO4 cathode material was successfully synthesized by a simple method of thermal explosion (TE) using hexamethylenetetramine (C6H12N4) as fuel. The crystalline phase, morphology and particle size of powders were characterized by X-ray diffraction, scanning electron microscope, particle size analyzer and transmission electron microscope measurements. And the electrochemical properties were investigated by galvanostatic charge–discharge tests and electrochemical impedance spectroscopy. The results indicated that the samples synthesized by TE showed an olivine crystal structure with space group Pnmb. In addition, both structure and particle size could be adjusted by the amount of C6H12N4 and the heat treatment temperature in the TE. When the amount of C6H12N4 was 30 wt%, the heat treatment temperature was 800 °C and the particle-size distribution fell in a range of 300–400 nm. Electrochemical tests indicated that the LiFePO4 sample synthesized in such conditions, without additional carbon coating and cation doping, shows a discharge capacity of 110.4 mAh g−1 and an excellent capacity retention rate of 87% after 50 cycles at 1 C.