Tài liệu Study the ionic conducting property of, LiCoO2 positive electrode

SUMMARY
The compound of LiCoO2 had been successfully prepared by using the solid state reaction method from the precursors of Li2CO3 and CoCO3 at 800oC in 12 hours. The structural properties were studied by X-ray diffraction and the ionic conducting property was examined by chemical impedance spectroscopy (CIS) technique in 1M LiClO4 + PC electrolyte. The analyzed results show that the prepared sample has the high-single phase of LiCoO2 with layers structure and the ionic conductivity is about 0.5.10-4 S.cm-1.
Key words: Electrochemical Impedance Spectroscopy (EIS), Ionic conducting.
INTRODUCTION
Due to the excellent performances such as high voltage, high energy density, and durable cycle charge characteristics, long time-life and friendly to the environment (compared to others kinds of battery), lithium-ion batteries have been used widely in portable electric device and power tools, electric vehicles and spacecraft like: cellular phone, notebook [1,2]. The main principle of Li-ion battery is based on the pulling part of the ions of Lithium from the positive electrode (more detail: from the material used as positive pole) and injecting into the space in the structure of negative electrode material. In commercial product and in study, the oxide compound of Li (LiCoO2, LiNiO2 ) which possesses the layer structure or spinel structure (LiMn2O4), where as, graphite, which also have the layer structure, is usually adopted as material for the latter electrode. Regularly, the material would be attached split onto the surface of a copper foil (for negative pole) or an aluminum foil (for positive pole) to form the electrodes of Li-ion battery. These electrodes must be completely separated to make safe and avoid the short-circuit. In processing, the Li ions depart from the positive electrode to the negative
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electrode and vice versa. So, the electrode materials must have the suitable structure that allows a large amount of Li ions to charge and discharge easily without any structural distorting [3, 4]. Therefore, in this paper, we report the process of synthesizing of LiCoO2 by solid state reaction method from the compounds of Li2CO3, CaCO3 at 800oC in 12 hours and the characterization of prepared sample.
EXPERIMENTAL
LiCoO2 was prepared by using the carbonate compounds of Lithium and Cobalt or from the oxidized substances of the metals above (the purity of about 99.9 %). The precursors were milled with the Li:Co mole-ratio of 1.2:1, after being made to be powder the mixture were pressed and experienced a heat treatment process in about 8 hours at 750oC with the increasing rate