Hydrothermal synthesis and characterization of LiMnPO4 for secondary lithium batteries /

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2014
Camcı, Esin
The mechanism in Li-ion batteries is based on the motion of Li+ ion between positive and negative electrodes. As Li-ion batteries have attracted much attention, the demand for high capacity and low cost electrode materials has increased. Lithium manganese phosphate (LMnP) is one of the most promising cathode materials. It highly satisfies the lithiation and de-lithiation process of Li-ion technology due to its olivine structure. Moreover, it has high theoretical capacity, it is safety and low cost. The drawback of LMnP is its poor ionic and electronic conductivity. The aim of this thesis is to optimize the hydrothermal process parameters for the synthesis of pure and well-crystalline LMnP, dope the Mn-site in the olivine structure with cobalt, chromium, molybdenum, vanadium and tungsten and eventually electrochemically characterize the samples to analyze the effect of doping. The structure and topography of the obtained powders were investigated with X-Ray Diffraction and Scanning Electron Microscopy. Also, the electrochemical characteristics were determined by different techniques; cycle tests, charge-discharge, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy. According to the results, doping process was successful to show better performance than pristine LMnP. After pure LMnP and its doped versions were analyzed, it is understood that cobalt and vanadium enhances the electrical and ionic conductivity of LMnP; whereas, chromium has an influence on the rate capability of LMnP