三维钴基过渡金属氧化物纳米线阵列的可控合成与储锂性能研究

发布时间：2018-02-03 10:06

本文关键词： 锂离子电池三维自支撑结构纳米线阵列钴基过渡金属氧化物　出处：《合肥工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：锂离子电池作为电化学能源储存系统中应用最为广泛的新能源器件目前在能量密度和功率密度上仍有较大的提升空间。负极材料相对于正极材料而言在决定上述两者的重要因素——比容量的提升上更具可行性,因此受到了大量的关注。而目前商用微米级块状负极材料由于其有限的电极动力学与传质过程而逐渐逼近其性能的极限,所以纳米结构被大量引入到负极材料的设计之中,以期获得更高的质量比容量。纳米电极结构的引入可以通过缩短离子扩散和电子传输路径显著改善电极动力学过程,可以带来诸如双电层电容、赝电容等新型储锂机制,可以稳定电极材料晶体结构。当然动力学活性的增强不可避免地就会带来热力学稳定性的减弱,纳米电极也由此极容易受到外界环境温度的干扰并趋向于团聚。更值得注意的是,纳米电极带来的高比表面积会导致高表面副反应,严重降低电池的库伦效率乃至于带来安全上的隐患。此外有机粘结剂对于整合纳米颗粒并连接纳米颗粒与集流体是必不可少的,但是这些电子绝缘体的引入将会严重影响电极的导电性能和电极与集流体之间的界面过程。针对上述前两个问题,微/纳多级结构和碳包覆被提出与应用。而为了避免使用粘结剂,在集流体上直接生长的自支撑结构被引入。在本文中,鉴于氧化钴(Co_3O_4)拥有890 m Ah/g的理论比容量和尖晶石结构方便于锂通道的构筑,因此通过水热反应的方法在三维网状泡沫铜基底上生长纳米结构。但是作为过渡金属氧化物,其储锂过程中转换反应机制所带来的体积膨胀是不可忽视的,这会带来较差的循环稳定性。在此研究中,碳包覆和镍、锰取代掺杂形成二元材料作为解决这一问题的两条路径并分别取得了不错的效果。通过碳包覆,三维氧化钴纳米线阵列电极在循环100圈之后达到了1484 m Ah/g的质量比容量,容量保持率为100%。而镍和锰取代掺杂分别形成钴酸镍和钴酸锰二元钴基三维纳米线阵列,它们在容量和稳定性上较氧化钴而言都有较大的改善,但是镍锰之间还是存在稳定性的差异(钴酸锰要优于钴酸镍),这与它们倾向于占据尖晶石结构A位还是B位的差异性有关。
[Abstract]:As the most widely used new energy devices in the electrochemical energy storage system, lithium ion battery still has a large space to improve the energy density and power density. The negative electrode material determines the above mentioned compared with the positive electrode material. The two important factors are more feasible than the increase of capacity. Because of its limited electrode dynamics and mass transfer process, commercial micron scale bulk anode materials are gradually approaching the limit of their performance. So nanostructures are introduced into the design of anode materials. The introduction of nano-electrode structure can significantly improve the electrode kinetic process by shortening ion diffusion and electron transport path, and can bring about such as double-layer capacitance. A new type of lithium storage mechanism such as pseudo-capacitance can stabilize the crystal structure of electrode materials. Of course the enhancement of kinetic activity will inevitably lead to the weakening of thermodynamic stability. As a result, nanocrystalline electrodes are easily disturbed by ambient temperature and tend to agglomerate. It is more important to note that the high specific surface area of nanometers will lead to high surface side effects. In addition, organic binder is essential to integrate nanoparticles and connect nanoparticles with fluid collection. However, the introduction of these electronic insulators will seriously affect the conductivity of the electrode and the interface process between the electrode and the collector. Micro / nano multistage structure and carbon coating are proposed and applied. In order to avoid the use of binder, self-supporting structure which grows directly on the collecting fluid is introduced. The theoretical specific capacity of 890m Ah/g and spinel structure are convenient for the construction of lithium channel. Therefore nanocrystalline structures were grown on a three-dimensional netted copper substrate by hydrothermal reaction. However as transition metal oxides the volume expansion caused by the transition reaction mechanism in the lithium storage process can not be ignored. In this study, carbon coating and nickel and manganese substitution for doping to form binary materials as two ways to solve this problem and achieved good results. The 3D cobalt oxide nanowire array electrode has a mass specific capacity of 1484 m Ah/g after 100 cycles. The capacity retention rate is 100. Nickel and manganese substituted doping form nickel cobaltate and manganese cobalt-based three-dimensional nanowire arrays respectively, which are better in capacity and stability than that in cobalt oxide. However, there is a difference in stability between nickel and manganese (manganese cobalt is superior to nickel cobalt, which is related to their tendency to occupy the A or B sites of spinel structure.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TM912

【相似文献】