Dissertation > Industrial Technology > Electrotechnical > Independent power supply technology (direct power) > Battery

Synthesis by Typical Method and Electrochemical Performance of LiFePO4 Cathode Material

Author MengYao
Tutor LiXueLiang
School Hefei University of Technology
Course Applied Chemistry
Keywords LiFePO4 Carbon source Solid-phase method Sol-gel method Rheological phase
Type Master's thesis
Year 2009
Downloads 324
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Lithium iron phosphate (LiFePO4) is a new lithium-ion battery cathode material, this material is non-toxic, environmentally friendly, abundant and inexpensive sources of raw materials, and cycle performance and excellent thermal stability with good prospects, especially in the power battery applications increasing attention by researchers. There is a drawback of low electrical conductivity, but this material limits its practical application. This paper describes the progress of the lithium-ion battery cathode material, battery cathode material LiFePO4 this stage lithium-ion battery research in the field. Main drawback of the material and its electrochemical properties, our study is a low-cost source of iron, LiFePO4 Synthesis and analysis of the impact of synthesis conditions on the electrochemical performance, the main contents are as follows: studying the typical structure of organic carbon on the electrochemical properties of synthetic products, organic carbon source as polyethylene glycol PEG (1000), soluble starch, lauric acid, adipic acid, 8 - hydroxy quinoline. The initial capacity of the product and the kind of the organic carbon source, when the carbon source is adipic acid, 8 - hydroxyquinoline, soluble starch, and lauric acid, its initial capacity for 90.6,106.8,120 and 132.9 mAh / g; PEG under the same experimental conditions, the best results, when the iron source and PEG molar ratio of 1:2, the highest discharge capacity 140.1mAh is / g. The experimental results show that: the selection of the conductive agent precursor has a great influence on product performance. 2 PEG and glucose as carbon sources on the electrochemical properties of synthetic products. When PEG glucose molar ratio is 1:1, the study found that when the change of the molecular weight of the PEG is between 400-6000, with the shortening of the carbon chain of PEG, the discharge capacity of the synthetic material to increase. The PEG400 performance will be better: LiFePO4 material at 0.15C discharge capacity of 163 mAh / g at 0.3C 150 mAh / g. PEG1000: glucose = 2:1, the sample has the best electrochemical performance, the reversible capacity of 139.9 mAh / g, the discharge capacity of 138.7 mAh / g after 20 cycles, the discharge capacity of 99.14% of its initial capacity. 3 sol? Gel method, with water as solvent, different ferric iron source Synthesis of LiFePO4 of ferric source structure and electrochemical properties of LiFePO4 material. (NH4) 3Fe (C6H5O7) 2, Fe (C6H5O7) · H2O, and Fe (NO3) 3.9 H2O as an iron source product, the first time at 0.1C discharge capacity was 76.8 mAhg-1, 119.1 mAhg-1 and 136.5 mAh / g, it can be seen that the water-soluble inorganic trivalent iron source is more conducive to quality materials. Li, P, Fe, C molecular level mixed flow in disguise prepared containing complexes as precursor materials, ferric iron, glucose and citric acid as a reducing agent for experimental synthesis of LiFePO4 cathode material. The material exhibits better electrochemical performance in its initial discharge specific capacity of 133.2 mAh / g and the 136.6mAh / g after 20 charge-discharge cycle capacity of only 3.83% and 0.51% attenuation. Using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) were used to characterize the product obtained the crystal structure, surface morphology. The results show that the grain size of the material synthesized by the above method for nanoscale electron micrograph showed that all products are LiFePO4 small particles are gathered together.

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