Effect Of Catalytic Heat Treatmeat On The Electrochemical Performance Of Mesco-Carbon Microbeads As Anode Material For Lithium-Ion Batteries

As a kind of high-performance anode materials for lithium-ion batteries, Mesocarbon microbeads have been paid much attention by worldwide researchers, due to their unique sphere flake structure and advanced electrochemical properties. Because MCMB for commercial usage need graphitization at about 3000°C, so how to improve usability, reduce the production cost and enhance the performance have become an important subject. This thesis was focused on the study of different surface modifications of green mesocarbon microbeads (MCMB). The preparation parameters, morphologies, structures and their relations were investigated in order to develop a novel carbon anode with higher properties, and to prompt the research and commercialization of lithium ion batteries.In this thesis, anode materials were prepared at the presence of ferric nitrate and ferric chloride, by the means of dipping-catalytic graphitization or Pre-oxidation-dipping-catalytic graphitization. The microstructure of these anode materials and their lithium insertion performance were studied by Scanning Electronic Microscopy (SEM), X-Ray Diffraction(XRD), charge-discharge and Alternating-current impedance measurements. The main research results of this dissertation are summarized as follows:It was found that graphitization degree of MCMB after catalytic heat treatment was improved. When these samples catalytically carbonized at 1500°C were used as anode materials for lithium ion batteries, the first reversible capacity reached to 233mAh/g, which was higher than the value 146mAh/g of sample without ferric nitrate addition, and showed excellent cyclability with the cycle efficiency approaching 100%. The kinetic properties of samples were characterized via AC impedance measurement. It was indicated that the proper ferric nitrate addition can reduce the resistance of SEI film and charge-transfer resistance, and improve the electrochemical performance of MCMB anode.The pre-oxidized green MCMB whose surface had more holes, favored the catalyst's plunging, made better catalyzed effect, and had more graphite crystallite at the surface, the interior still were the low temperature carbon structure, the kind of structure improved the MCMB surface and the electrolyte contact reaction, enhanced its charge-discharge efficiency and the circulation performance, displayed the better electrochemistry performance.