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Research on Synthesis and Modification of Nanostructured LiMn2O4 for Lithium-ion Batteries

Author: XiangRuMing
Tutor: LiXueLiang
School: Hefei University of Technology
Course: Applied Chemistry
Keywords: Lithium ion battery Cathode materials Nano- LiMn2O4 Modified
CLC: O614.111
Type: Master's thesis
Year: 2007
Downloads: 165
Quote: 1
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Abstract


Spinel LiMn2O4 is a new kind of cathode material for lithium-ion battery. Its theoretical specific capacity is 148mAh/g. LiMn2O4 has received much attention as a cathode material because of the high voltage required for lithium insertion and its lower price and better compliance with environment and so on. However, LiMn2O4 often shows a lower storage capability, its cycle performance at the high rate should be improved. On the base of reviewing the development of lithium ion battery and its cathode materials in detail, LiMn2O4 with nanostructure was chosen as cathode material and their synthesis and modification were studied.Hydrothermal synthesis、sol-gel method and wet ball-milling promoted solid state reaction were adopted to prepare nanostructured LiMn2O4. The products were investigated by X-ray diffractometer （XRD）, Transmission electron microscopy （TEM） and field emission scanning electron microscopy （FE-SEM）. Moreover, we used charge-discharge test to study specific capacity and cycle performance, cyclic voltammogram （CV）, electrochemical impedance measurements （EIS） and its equivalent circuit to discuss electrochemical reactive mechanism. The results show that the crystal size of the materials prepared by the above methods reach to nano-grade, particularly, the products obtained by hydrothermal method and wet ball-milling promoted solid state reaction had a much smaller particle size and a narrower particle size distribution and the high rate discharge-capability was improved to a certain extent. Meanwhile, the modified materials were also studied on the basis of LiMn2O4 with nanostructure.The study showed that LiMn2O4 prepared by hydrothermal method firstly using MnO2 as precursors had a good electrochemical properties, its initial specific charge capacity was up to 120mAh/g （at 0.2C discharge rate）. Wet ball-milling promoted solid state reaction reduced the heating temperature and the sintering time; optimized the synthesing route compared to the traditional solig state reaction to prepare LiMn2O4. The electrochemical properties were improved.Finally, we studied the modified materials of nanostructured LiMn2O4 （doping and composition）, the results indicated that Ag-doped and LiMn2O4/carbon aerogels nanocomposite materials can enhance the electronic conductivity efficiently and improve its electrochemical performance; V-doped nanostructured LiMn2O4 showed reduced irreversible capacities, improved cycling performance; The addition of VO2 （B） to LiMn2O4 increased the electrochemical window, utilized a large discharge capacity in the 3V region efficentlty, enhanced the specific capacity of the material dramatically.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds > Part Ⅰ family metal elements and their compounds > Elements of the alkali metal ( I A tribe) > Lithium Li
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