【作者】 文志刚；

【导师】 郑峰；

【作者基本信息】 中南大学 ， 材料科学与工程， 2013， 博士

【摘要】 金属氧化物纳米材料具有独特的物理化学性质,其在光电器件、传感器、催化、磁学和锂离子电池等领域有广泛的应用前景。纳米材料的结构和形貌对其性能有重要的影响。发展新的合成方法,探索其生长机制,对于系统研究纳米材料结构与性能的关系,实现工业生产具有重要的意义。本文设计了一系列合成CoO、CuO、Cr2O3、SnO2及其复合材料的新方法,详细探讨了部分材料的反应机理,检测了它们在锂离子电池中的电化学性能。通过大量的探索和实验,取得了一些有意义的成果。1、设计了一种水热法合成SnO2纳米棒束花的新方法。利用X射线衍射仪、场发射扫描电镜、透射电子显微镜检测仪器详细研究了SnO：纳米棒束花的新颖结构。检测结果显示纳米棒束花是由四方状的纳米棒组成,棒的尺寸大小可以通过改变SnCl4浓度来调控。在详细分析实验结果的基础上,提出了SnO：纳米棒束花的形成机理。电化学测试表明SnO2纳米棒束花具有良好的储锂容量和循环性能,0.1C时循环充放电40次后,放电容量保持在694mAhg-1。2、发展了一种制备疏松结构SnO2纳米球的水热-分解新路线。通过热重分析检测研究了整个分解过程。疏松结构SnO2纳米球直径为300nm左右,是由粒径26nm左右的粒子自组装而成。疏松结构SnO2纳米球的首次放电容量为1520mAh g-1,充电容量为724mAhg-,循环充放电30次后容量保持在522mAh g-。得益于疏松结构,SnO2纳米球具有较大的储锂容量和较好的循环性能。3、采用葡萄糖为碳原,在150℃下水热反应10小时后制备了单分散性好的纳米SnO2-C复合材料。对其进行详细表征,结果证实SnO2纳米粒子均匀地分散在无定型碳中。电化学检测表明,这种纳米SnO2-C复合材料首次放电容量为1321mAhg-1,充电容量为735mAhg-,循环充放电60次后充电容量是486mAhg-1,循环性能比较好。4、设计了一种通过溶剂热法合成CoO实心纳米球的新方法。其反应温度低,操作简单,适合于工业应用。通过对样品的各种检测证实,制备的样品是高纯CoO实心纳米球,其直径为100～300nm。探讨了油酸的用量对CoO实心纳米球形貌的影响,提出了可能的形成机理。在0.1C时,CoO实心纳米球首次放电容量和充电容量分别为1598mAh g-1和905mAh g-1。5、以SiO2纳米球为模板,设计了一条合成CoO空心纳米球的新路线。详细阐述了CoO空心纳米球的形成机理。通过恒电流充放电实验证实,在电流密度0.1C时,CoO空心纳米球首次放电容量是1640mAh g-1,并且CoO空心纳米球的循环性能比CoO实心纳米球更好。6、发展了一条制备CuO纳米粒子和多孔微米球的水热合成新路线。详细分析了pH值和十二烷基苯磺酸钠用量对CuO多孔微米球形貌的影响。检测发现CuO纳米粒子和CuO多孔微米球的首次充电容量分别为475mAh g-1和564mAh g-1,循环充放电30次后,其充电容量分别为272mAh g-1和477mAh g-1。7、通过水热反应得到前驱体,再煅烧前驱体,制备了Cr2O3纳米粒子,其粒径在30～60nm之间。探索了pH值对其形貌的影响。检测了Cr2O3纳米粒子的电化学性能,发现其首次放电容量为1222mAhg-1,充电容量为781mAh g-1,循环30次后,其充电容量为327mAh g-1。更多还原

【Abstract】 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.更多还原