Lithium Negative Moo <sub> 2 </ Sub>-c Preparation And Characterization Of Hollow Composite

Lithium ion batteries (LIB), as power sources have attracted special attention in the scientific and industrial fields due to their high energy density, high electromotive force, no memory effect and long cycle life as compared with the traditional second batteries. Carbon materials have commonly been used as anodes in lithium ion battery systems, and carbon microspheres due to their unique spherical structure have received widespread attention. But many efforts should be made to improve the existing carbon material or develop new electrode material because of a limitation in the lithium ion capacities of carbon materials.In this dissertation, we had analyzed and summarized the newest development in the research about anode materials of lithium ion batteries and investigated the influence of different synthetic and washing conditions on the shape of the carbon microspheres. Three different shapes of carbon microspheres, grid carbon microspheres, hollow carbon microspheres and solid carbon microspheres, were eventually synthesized. The microstructure and morphologies of these materials were characterized by SEM, TEM, XRD and BET. The electrochemical performances were evaluated by galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectra in detail. The main results are given as follow.1. The carbon microspheres with different shapes were prepared by using F108as surfactant,2,4-dihydroxybenzoic acid and formaldehyde as reactants, L-lysine as catalyst. We investigated the influences of different synthetic and washing conditions on the shape of the carbon microspheres, three different shape carbon microspheres, grid carbon microspheres, hollow carbon microspheres and solid carbon microspheres, were synthesized finally. TEM analysis shows that the shape of the carbon microspheres plays an important role in the lithium-storage capacity when they are used as anode materials for rechargeable lithium-ion batteries. The W-48anode material shows the optimal electrochemical performance, the initial reversible capacity is865mA h g-1, the average of reversible capacity is544mA hg-1in50cycles and it still maintains492mA hg-1which is higher than graphite's theoretical capacity that is372mA h g-1. 2. Several hollow MoO2-C microspheres were obtained by using F108as surfactant,2,4-dihydroxybenzoic acid, formaldehyde and MoO3as reactants, L-lysine as catalyst. SEM and TEM analysis show that the diameter of the microspheres is700nm, the wall thickness60nm, and the particle of MoO212nm. BET analysis indicate that the specific surface area of the material became smaller and smaller as the amount of MoO3is increased. The electrochemical performance of MoO2-C composite electrode is much better than Pure-C electrode's. The MoO2-C-2anode material has the optimal electrochemical performance that the initial reversible capacity is574.2mA h g-1, the average of reversible capacity is635.4mA hg-1in80cycles, and it still maintains618.9mA h g-1which is56.9%of the initial reversible capacity after80cycles.