Synthesis And Modification Of The Lithium-ion Battery Cathode Materials For Lithium Iron Phosphate

Lithium iron phosphate is considered a promising cathode material for its good performance, low price and environmentally friendly.Pure LiFePO4 was synthesized through a new co-precipitation method. LiFePO4 was also prepared by using sol-gel. Temperature, heating-time and the amount of carbon sources' effect on the electro-chemical performances of LiFePO4 was studied as well.LiFePO4 was also doped with Mg2+ to synthesis Li0.99Mg0.01FePO4.1. Co-precipitation Method:The reactants were added synchronously. The flow speed was controlled to achieve one-step precipitation. The first-cycle discharge capacity reached 117.4mAh/g, while after 50 cycles,90% capacity could be reserved. X-ray diffraction pattern showed the main absorption peak corresponded accurately to the standard card. LiFePO4's scale was photographed by TEM. The picture showed the particle size was about150-250nm with carbon phase on its surface.2. Sol-Gel Method:The relations between LiFePO4's electrochemical performances and the temperature, time, the amount of citric acid added was researched. When the molar ratio of LiAc·2H2O,Fe(NO3)3·9H2O,NH4H2PO4 and citric acid was set to1:1:1:1 and heated at 650℃for 8hours, the LiFePO4 synthesized get the best performance. With 1%Mg2+ in the LiFePO4, Li0.99Mg0.01FePO4's electrochemical performance and its ability to maintain large current also increased.