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Iron-based Materials Are Used As Cathode Materials For Lithium Ion Batteries

Posted on:2017-03-22Degree:MasterType:Thesis
Country:ChinaCandidate:R YangFull Text:PDF
GTID:2351330503488874Subject:Chemical processes
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In this paper, lithium ion battery cathode material is studied. FePO4 and LiFePO4 is prepared by microwave liquid and solid phase crystallization method, respectively. Firstly, microwave reaction time and temperature of liquid phase crystallizationa effect on the crystallization yield are studied. The influence of metal ion doping on FePO4 electrochemical performance is studied at the same time. To characterize the crystal structure, morphology and electrochemical properties of the product, we use X- ray diffraction(XRD), scanning electron microscopy(SEM), inductively coupled plasma mass spectrometry(ICP-MS), electrochemical analysis and so on. Afterwards, LiFePO4 is prepared by solid phase crystallization and glucose, Li2CO3 and FePO4 are used as raw materials. The reaction time affect on the influence of the Li FePO4 properties is studied. XRD?SEM and particle size analysis are used to characterize the LiFePO4 properties. On this basis, the influence of metal ion doping on Li FePO4 properties is characterized and analyzed.Experiment results showed that reaction time and temperature both had effects on production ratio P:Fe=6:1. The nucleation rate in reaction system corresponded to the increase of temperature and the production rate within a certain period of time. On this basis, Cr3+?Mg2+?Zn2+were doped on FePO4. Ion doping had a certain effecton FePO4 properties. Mg2+ doping had a remarkable effect on FePO4 and the initial discharge specific capacity of FePO4 samples with Mg2+ doping increased 2.3 times compared with pure FePO4.In the preparation of LiFePO4, the reaction time had a certain effect on electrochemical properties of LiFePO4.Experiment result showed that under the condition of 8h reaction time, LiFePO4 had a remarkable electrochemical properties. When doping with metal ion, the metal ion which had different valence with Fe2+ had greatly changed the electrochemical Li FePO4 properties compared to the pure LiFePO4.Among which,V5+ had the greatest effect on LiFePO4. After doping of V5+on LiFePO4, its initial discharge specific capacity increased from 133.8 mAh/g to 158.5 mAh/g and perpormed good rate discharge property.
Keywords/Search Tags:Microwave Radiation Crystallization, Iron phosphate, Lithium iron phosphate, Doping, Solid phase method, Mechanism
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