Synthesis And Characterization Of Micro-/nanostructured Metal Oxides And Their Applications For Lithium-ion Battery

Owing to their unique physical and chemical properties, metal oxide nanomaterials have potential applications in photoelectric devices, sensors, catalysis, magnetics and lithium-ion battery. Structure and morphology of nanomaterials have great influence on their properties such as surface effect, small-size effect and quantum size effect. Developing new synthetic methods and investigating their formation mechanisms should be a key precondition to understand the relation among structure and properties and industrial applications. In this dissertation, new synthetic methods of nanosized CoO, CuO, Cr2O3, SnO2and SnO2-carbon composite have been developed. Their formation mechanisms have been explored in detail. And, electrochemical properties of selected samples of each oxide as anode in lithium-ion battery have been tested. Several new and interesting results have been achieved and listed as the followings.1. A new hydrothermal synthetic method has been established to synthesize flowerlike SnO2nanorod bundles. Structure details of flowerlike SnO2nanorod bundles were studied by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy, respectively. Microscopy images showed that the flowerlike SnO2nanorod bundles are consisted of tetragonal nanorods with size readily tunable by changing the concentration of SnCl4. Based on experimental results, a probable formation mechanism of SnO2nanorod bundles has been proposed. Results on electrochemical properties showed that SnO2nanorod flowers as anode in lithium-ion battery possessing improved discharge capacity of694mAh g-1up to40th cycle at0.1C.2. A new hydrothermal-decomposition route was developed to prepare porous SnO2nanospheres. Decomposition process of precursor for making porous SnO2nanospheres was studied by DSC-TGA curve. These porous SnO2nanospheres of300nm in diameters are composed of numerous nanoparticles around20～35nm. The first discharge and charge capacity of porous SnO2nanospheres was1520mAh g-1and724mAh g-1, respectively, while the discharge capacity after30cycles retained at about522mAh g-1. Porous SnO2nanospheres have large capacity and good cycling performance, due to their unique porous nanostructure.3. Monodispersed SnO2-carbon composite has been synthesized by hydrothermal route using glucose as carbon sources and reacted with SnO2at150℃for24h. SnO2-carbon composite has been characterized in detail with SnO2nanoparticles dispersed uniformly in amorphous carbon. Electrochemical tests showed that first discharge and charge capacity of SnO2-carbon composite as anode materials was1321mAh g-1and735mAh g-1, respectively. The charge capacity after60cycles retained at about486mAh g-14. A new solvothermal method has been designed to synthesize solid CoO nanospheres by esterification reaction. Compared to traditional solid state reaction, operation of solvothermal reaction is relatively simple with mild synthetic temperature and therefore of promising for industrial application. High-purity solid CoO nanospheres of100～300nm in diameters were characterized. Effect of concentration of oleic acid on morphology of samples has been investigated and possible formation mechanism of solid CoO nanospheres has been proposed. The first discharge capacity and charge capacity of solid CoO nanospheres as anode are1598mAh g-1and978mAh g-1at0.1C, respectively.5. A new synthetic route was designed to prepare hollow CoO nanospheres through using SiO2as template. Formation mechanism of hollow CoO nanospheres was introduced in detail. Galvanostatic discharge-charge experiments showed that first discharge capacity of hollow CoO nanospheres was1640mAh g-1at0.1C, and hollow CoO nanospheres as anode here showed better cycle performance compared to that of solid CoO nanospheres.6. A new hydrothermal synthetic route was developed to fabricate CuO nanoparticles and porous CuO microspheres. The effects of pH and concentration of sodium dodecylbenzensulfonate were discussed on morphology of porous CuO microspheres. Electrochemical tests showed that first charge capacity of CuO nanoparticles and porous CuO microspheres was475mAh g-1and564mAh g-1, respectively. Charge capacity of CuO nanoparticles and porous CuO microspheres after60cycles retained at272mAh g-1and477mAh g-1, respectively.7. The precursor of Cr2O3was fabricated by hydrothermal method while Cr2O3nanoparticles of30-60nm in diameters were obtained by annealing of the precursor. Effect of pH on morphology of Cr2O3nanoparticles was investigated. The first discharge capacity and charge capacity of Cr2O3nanoparticles as anode are1222mAh g-1and781mAh g-1at0.1C, respectively. Charge capacity of Cr2O3nanoparticles as anode after30cycles is327mAh g-1.