One-Pot Synthesis of LiFePO<sub>4</sub> Nano-Particles Dispersed in N-Containing Melamine-Formaldehyde Carbon Matrix as the Cathode Materials for Large Scale Lithium Ion Batteries

Abstract

LiFePO4 is considered as the promising cathode material for a large-scale Li batteries used in electrical vehicles (EVs). However, a practical use of LiFePO4 cathode is limited by its low ionic conductivity, resulting in low battery’s power performance. This work, a facile and practical method to promote ionic conductivity and capacity of LiFePO4 was developed by dispersing LiFePO4 nanoparticles into a porous nitrogen-riched carbon matrix by employing one-pot synthesis approach. The N-containing carbon porous matrix was prepared by utilizing melamine-formaldehyde (MF) resin as the N-containing carbon precursor and Pluronic F127 as the porous template. The pseudo capacitive effect attributed from lone-pair electrons into melamine functional group was expected to support Li ion transport. After carbonization at 600 °C, uniform LiFePO4 nanocomposite clusters with an average size of about 50-300 nm were obtained. The influence of the molar ratio between pluronic F127 and melamine-formaldehyde (i.e. F127:MF molar ratio as 0:1, 0.03:1, 0.3:1) on the LiFePO4 nanocomposite’s morphology and crystalline structure was investigated by using scanning electron microscope and X-ray diffraction technique. The results show that increasing F127 concentrations support more porous structure formation, leading to a higher surface area but does not affect the LiFePO4 nanocrystalline structure. According to the highest surface area, the N-doped carbon coated LiFePO4 composite product obtained from the molar ratio of F127:MF as 0.3:1 exhibited highest discharging specific capacity of 158.1 mAh g-1, at a rate of 0.1 C and also shows high cycle stability.