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℃.