Synthesis,Characterization And Electrochemical Performance Study Of LiFePO₄ For Lithium Ion Batteries

Olivine-structured LiFePO4 is considered as a promising cathode material for lithium-ion batteries,due to its advantages such as relatively high capacity,abundant raw materials,environmentally benign,inexpensive price and high safety.On the base of reviewing the development of lithium-ion battery and its cathode materials in brief,the synthesis of LiFePO4 was chosen to be studied.In this paper,LiFePO4 was synthesized by carbon-thermal reduction and sol-gel method.Then the morphology,structure of particles and electrochemical performance were characterized.The major research contents and conclusions of carbon-thermal reduction method are as follows:The effects of sintering temperature on electrochemical properties were investigated.LiFePO4 was synthesized by carbon-thermal reduction method with Li2CO3,FeC2O4·2H2O,NH4H2PO4 and PVA.The starting mixture was calcined at 450? to get the precursor and then calcined at 600 ?/650 ?/700 ?/750 ?.600 ? was selected as the optimum synthesis temperature in the experiment.The effects of different carbon sources on electrochemical properties were investigated.LiFePO4 was synthesized by carbon-thermal reduction method with Li2CO3,FeC204·2H2O,NH4H2PO4 and 15%starch/sucrose/lemonade/PVA.The starting mixture was calcined at 450 to get the precursor and then calcined at 600 ?.PVA was selected as the optimum carbon source in the experiment.The effects of carbon contents on electrochemical properties were investigated.LiFePO4 was synthesized by carbon-thermal reduction method with Li2CO3,FeC2O4·2H2O,NH4H2PO4 and 15%/20%/25%PVA.The starting mixture was calcined at 450? to get the precursor and then calcined at 600?.20%was selected as the optimum carbon content in the experiment.The effects of sintering time on electrochemical properties were investigated..LiFePO4 was synthesized by carbon-thermal reduction method with Li2CO3,FeC2O4·2H2O,NH4H2PO4 and 20%PVA.The starting mixture was calcined at 450? to get the precursor and then calcined at 600 ? for 5 h/7 h/9 h.7 h was selected as the optimum sintering time in the experiment.The results show that the LiFePO4 with the capacity of 140 mAh·g-1 was prepared with Li2CO3,FeC204·2H2O,NH4H2PO4 and PVA at the sintering temperature of 600?.LiFePO4 synthesized by sol-gel has better volume stability,smaller energy consumption compared with carbon thermal reduction method.So sol-gel and carbon thermal reduction method was conjunctive used in this paper.The major research contents and conclusions of carbon-thermal reduction method are as follows:The effects of pre-sintering temperature on electrochemical properties were investigated.LiFePO4 was synthesized by sol-gel with FeC2O4·2H2O,NH4H2PO4,LiOH dissolved in(CH2OH)2.The starting mixture was reacting at 90?/110?/130?/150? to get the precursor and then calcined at 700?.110? was selected as the optimum pre-sintering temperature in the experiment.The effects of sintering time on electrochemical properties were investigated.LiFePO4 was synthesized by sol-gel with FeC2O4·2H2O,NH4H2PO4,LiOH dissolved in(CH2OH)2.The starting mixture was reacting at 110? to get the precursor and then calcined at 700 ? for 5 h/6 h/7 h/8 h.7 h was selected as the optimum sintering time in the experiment.The effects of different carbon sources on electrochemical properties were investigated.LiFePO4 was synthesized by sol-gel with FeC2O4·2H2O,NH4H2PO4,LiOH dissolved in(CH2OH)2.The starting mixture was reacting at 110? to get the precursor and then calcined at 700 ? with PVA/lemonade/starch.PVA was selected as the optimum carbon source in the experiment.The results show that the LiFePO4 with the capacity of 132 mAh·g-1 was prepared with FeC2O4·2H2O,NH4H2PO4,LiOH dissolving in 110?(CH2OH)2 and calcined at the sintering temperature of 700?.