Physical and electrochemical properties of LiFePO4/carbon composite synthesized at various pyrolysis periods

Aluminum-doped lithium iron phosphate was synthesized with a modified sol-gel process. The sol-gel derived cathodes show much higher conductivity than those prepared by a solid-state method. The conductivity is 8 x 10(-2) S cm(-1) for the Al-doped LiFePO4/carbon composite powders synthesized at 850 degrees C for 2 h, as determined using AC impedance spectroscopy. The electrodes consisting of the Al-doped LiFePO4/carbon composite powders were fabricated for the electrochemical characterization and showed a specific capacity of about 150 mAh g(-1) at C/40 rate. Not only the conductivity A the crystal lattice but also the conductivity of the grain boundary is enhanced for the nano-sized Al-doped LiFePO4/carbon composite powders. (c) 2005 Elsevier B.V. All rights reserved.