| Lithium iron phosphate,LiFePO4,has recently attracted significant interest because of its large theoretical capacity of 170 mAh/g,excellent thermal stability in fully charged state,low cost and environmentally friendly components.However,there are some disadvantages for LiFePO4 such as low electric conductivity,low tap density and poor low-temperature character,which limit its applications in large scale.The aim of the paper focus on the preparation of the composite materials of LiFePO4 powder coated with conducting polymers.Effects of the preparation conditions,such as precursor material,annealing temperature et al.,on the structure and electrochemical properties of LiFePO4 were studied.Using TG-DTG,SEM and electrochemical charge-discharge tests,the preparation processes,the modification of materials,the structural characterization and the electrochemical properties of the olivine lithium iron phosphate as cathode materials for rechargeable lithium batteries were systematically investigated.The carbon content was optimized,and the material also displays a more stable cycle-life than the others.The open circuit voltage and the capacity for LiFePO4 have been measured.The results indicated that the improved co-precipitation method was an effective route to improve the electrochemical of LiFePO4/C material.The composite materials of LiFePO4 powder coated with polyacenic semiconductor materials?PAS? were successful prepared.SEM images and TG thermogravimetric analysis of the obtained carbon coating microspheres suggest that LiFePO4 powder was successfully encased within the carbon gel microspheres.The electrical conductivity of the composite materials could get to 10(-2S·cm-1.It was found that the composite LiFePO4 material exhibits excellent capability with initial discharge capacity more than 212.4 mAh·g-1.The discharge capacity goes up to 346mAh/g after ten times of cycle. |
PDF Full Text Request