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Research on Synthesis and Modification of Layered LiMnO2 Cathode Materials for Lithium-ion Batteries

Author: LiuDaJun
Tutor: LiXueLiang
School: Hefei University of Technology
Course: Applied Chemistry
Keywords: Lithium ion battery o-LiMnO2 Electrochemical properties Doping Complex
CLC: TM912
Type: Master's thesis
Year: 2009
Downloads: 130
Quote: 2
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Abstract


Based on the papers in the detailed review of the lithium-ion battery cathode material progress, select the layered LiMnO 2 as the research object, its preparation, composite and doping modification research. Step solid-phase method, using glucose as the carbon source, reducing atmosphere successfully direct by LiOH, MnO 2 , synthesized the o-LiMnO , 2 < / sub> / Li 2 MnO 3 cathode material; 750 ℃ ??heat treatment of MnO 2 Mn get 2 O 3 Mn source, respectively, were synthesized by solid-phase method and hydrothermal method o-LiMnO 2 cathode material; same time, Mg and Mo elements LiMnO 2 materials doped. Manganese the source synthesizer o-LiMnO to Mn 2 O 3 2 compared to glucose as the carbon source synthesis of o-LiMnO 2 process without MnO 2 high temperature pretreatment greatly simplify the synthesis process, shortening the synthesis cycle. Using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and other means of product phase and morphology characterization; investigated at the same time through the charge-discharge test and AC impedance test obtained sample electrochemical performance, the use of non-situ XRD patterns of charge-discharge process LiMnO 2 / Li 2 of MnO 3 composite phase change . Were LiMnO 2 carbon content in the materials and composite materials of Li / Mn ratios determined by elemental analyzer and plasma atomic emission spectrometer. On the basis of a large number of experimental data, we obtained the raw material ratio, reaction temperature and other conditions affect the performance of the synthesized product. The results show that: the synthesis of o-LiMnO 2 sample optimal conditions for Li: Mn: C molar ratio for 5:4:2,750 ℃ ??calcined 12h; samples with good electrochemical performance, 15 cycles After discharge capacity of 122 mAh · g -1 ; In obtained 0.23Li , of MnO , 2 3 · 0.77LiMnO 2 < / sub> Materials and o-LiMnO the different 2 3V and 4V platform, showing 4.1V and 2.5V charging and discharging platform, the charging and discharging process exists in part to MnO 2 transformation, this transformation has great impact on the electrochemical properties, the phenomenon of the discharge efficiency of greater than 100%; after 30 cycles the discharge capacity of the composite material is 21 8 mAh · g -1 , significantly improves the o-LiMnO 2 of the charge-discharge characteristics. The Mn 2 O 3 manganese source hydrothermal method o-LiMnO of synthetic 2 performance is superior to the results of the solid-phase method; Part of LiMnO 2 doping modification, the results show: Mg-doped molar fraction of 10%, after 20 cycles the discharge capacity was maintained at more than 86.27%, the cycle performance of the battery is doped than no Mg samples have significantly improved; doped Mo on the properties of the materials modified without the effect of Mg-doped, but in the same molar fraction doping is also effective to improve the cycle performance. Meanwhile, of LiMnO 2 / VO 2 (B) the electrochemical properties of the composites were also studied.

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