Preparation And Characterizations Of Monodispersed Spherical LiFePO4Powders

LiFePO4is one of the most potential cathode materials which have a high theoretical capacity (170mAh/g) and voltage (about3.5V versus Li/Li). It also has good stability both at room temperature and high temperature. Besides, it is environmentally benign and inexpensive. However, LiFePO4have some fatal problems including its low electronic conductivity, low lithium ion diffusivity, and low tap density. It is important for tap density to control the morphology of powders. LiFePO4powders were prepared by different methods in the paper. The powders were characterized by SEM, XRD. Some results were obtained as following:(1) Monodispersed LiFePO4microspheres were successfully prepared by hydrothermal method with ethanol as additive. These microspheres show a quite uniform size distribution of about10μm and are composed of many densely aggregated nanoparticles and interconnected nanochannels. The effect of ethanol on the micromorphology, disperse and phase were investigated. The content of ethanol don’t have impact on the phase of LiFePO4powders. When the volume ratio of ethanol/water are2:5and3:5, the gooder disperse spherical powders were acquired. The tap density is1.34g/cm.(2) Monodisperse hydration ferric phosphate particals were prepared by sol-gel method using Fe(ClO3)3and H3PO4as raw materials. The size of spherical particals decreased with increasing the solute concentration or raising the aging tempetature, but the dispersion of spherical particals didn’t have improved greatly.(3) Ferric phosphate obtained from calcining hydration ferric phosphate particals have sintered in large areas. So we couldn’t obtain monodisperse and pure LiFePO4because raw materials didn’t mix uniformly. LiFePO4nanometer spheres were directly prepared by solid state method using hydration ferric phosphate as precursor. The morphology of inheritance of hydration ferric phosphate has improved greatly. So monodispersed LiFePO4/C spherical nano-powders can be obtained.