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Synthesis and Modification of Li3V2（PO4）3 as Cathode Materials for Li-Ion Batteries

Author: ZhuangXinJuan
Tutor: LiZuo
School: Harbin Institute of Technology
Course: Chemical Engineering and Technology
Keywords: Lithium ion battery Cathode material Li3V2 PO4 3 Sol-gel method Carbon-coated Doping
CLC: TM912.9
Type: Master's thesis
Year: 2009
Downloads: 99
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Abstract


The monoclinic structure Li 3 V 2 (as PO in 4 ), 3 cathode material has theoretical specific capacity discharge platform for higher performance and cycle stability and the advantages of the great development potential of a new type of lithium ion battery cathode material. But its drawback is that the electronic conductivity is relatively low, the large-current discharge performance of the material is poor. To overcome this drawback, this article use the sol gel Preparation of Li 3 V 2 (the PO 4 ) 3 sintering temperature, sintering time on the material structure and electrochemical properties, and to optimize the synthesis process. Carbon-coated material properties of the material, the metal ion doping modification. By thermogravimetry - differential thermal analysis (TG-DTA) to study the material precursor weightlessness and suck exothermic process, examines the structure of the material by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and surface morphology, the use of charge-discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) testing methods to characterize the electrochemical properties of the material. First studied Li 3 of V 2 (PO 4 ), 3 cathode material for the synthesis process. The results show that: the sol-gel method LiCO 3 the Li source V 2 O 5 V source, citric acid as a carbon source, optimal synthesis process of sintering at 800 ℃ 16h, prepared Li 3 V 2 (as PO in 4 ), 3 pure phase monoclinic structure in the voltage range of 3-4.8V, 0.1C magnification, the first discharge capacity of 169mAh · g -1 , after 50 cycles, the capacity retention rate of 84 %. Second coated carbon material properties. The coated carbon can make better contact between the material particles, improve the electrochemical properties of the material. The results show that: citric acid coated 30mass%, the samples synthesized in this condition in the voltage range of 3-4.3V, 0.1C rate, the first discharge capacity is 129mAh · g -1 < / sup>, the capacity retention rate of 99.2% after 50 cycles. In addition research the Ti 4 and Fe 3 doped material properties. The results show that the material does not change the structure of the sample grain refinement: doped with a small amount of Ti 4 and Fe 3 . AC impedance and cyclic voltammetry test results show that the the the the Ti 4 and Fe 3 , a small amount of doping will reduce the charge transfer resistance of the material to improve the electrochemical properties of the material. The charge-discharge test results show that a small amount of the the Ti 4 and Fe 3 doping can improve the rate discharge performance, Li 3 (V 0.9 Ti 0.1 ) 2 (PO 4 ) 3 3-4.8V voltage range within 2C magnification sample the first discharge capacity is 167mAh · g -1 , After 50 cycles, the capacity retention rate of 89.8%. Li 3 (V 0.9 Fe 0.1 ) 2 (PO 4 ) 3 3-4.8V voltage range 0.1C rate, the sample of the first discharge specific capacity of 191mAh · g -1 After 50 cycles, the capacity retention rate 84.7%.

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CLC: > Industrial Technology > Electrotechnical > Independent power supply technology (direct power) > Battery > A variety of materials, battery
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