锂离子电池用锡基、铁基负极材料的制备及性能研究

发布时间：2018-06-01 23:02

本文选题：二氧化锡 + 三氧化二铁　；参考：《南京航空航天大学》2014年博士论文

【摘要】：锂离子电池具有高开路电压、低自放电率、较长的循环寿命、高比能量、无记忆效应等特点,被称为二十一世纪的绿色能源和主导电源,具有广泛的应用前景。而锂离子电池的性能主要取决于正极材料、负极材料以及电解质材料的结构和性能,开发廉价高性能的正、负极材料一直是近年来研究的热点。针对负极材料来说,目前商业化的负极材料以石墨类为主,但石墨的理论容量只有372 m A h/g,已无法满足高能量锂离子电池的需求。因此,开发容量更高、更安全的新型负极材料具有重大的意义。在众多的负极材料当中,Sn O2和Fe2O3是两种极具潜力的材料。但由于这些氧化物的导电性很差,并且在充放电过程中,随着锂离子的嵌入和脱出,Sn O2和Fe2O3会产生巨大的体积变化,导致材料的粉化,造成材料的容量迅速衰减。如何提高这些氧化物的循环性能也成为了该领域的一个重要课题。既然碳材料具有很好的循环性能,而氧化物材料具有较高的比容量,如果能把碳材料和氧化物结合起来,发挥二者的优势,弥补单一材料所具有的缺陷,就有可能获得高容量、循环性能良好的负极材料。本文采用不同的方法制备了Sn O2/graphene、Sn O2/FGS、Sn O2/MCNF以及Fe2O3/MCNF、Fe2O3/carbon foam复合材料,研究了孔隙度、负载量、电流密度及不同载体等因素对产物电化学性能的影响。(1)采用原位合成的方法,以Sn Cl2?2H2O为锡源,以氧化石墨(GO)为基体,以极性较弱的乙醇作为溶剂,通过Sn2+与氧化石墨之间的氧化还原反应,制备了具有多孔结构的Sn O2/graphene复合材料。多孔结构的存在,有利于电解液的传输和电荷的转移;石墨烯的存在,一方面为Sn O2提供了良好的导电网络,另一方面能够对Sn O2的体积变化起到缓冲的作用。电化学测试结果表明,复合物电极材料表现出良好的电化学性能。(2)以Sn Cl2·2H2O和GO为原料,在未加入任何添加剂的情况下,通过水热合成的方法制备了Sn O2/graphene复合物,讨论了不同负载量复合物的电化学性能以及材料微孔孔隙度对产物性能的影响,结果表明,微孔孔隙度较高的样品表现出较好的电化学性能,这是因为微孔的存在能够提供较高的活性面积。采用微波的方法对水热合成进行了改进,将反应时间缩短至2 min,研究了微波反应时间对产物性能的影响,结果表明,微波时间为2 min左右时,原料已经完全反应,大大缩短了复合物的制备时间。(3)将文献所述的方法加以改进,制备了高比表面积的介孔碳纳米纤维(MCNF)阵列,MCNF具有很高的比表面积,较大的孔容量和石墨化结构,是一种优良的载体;采用低温下硝酸盐热分解的方法制备了Fe2O3/MCNF复合材料,并研究了其作为锂离子电池负极材料的电化学性能,讨论了复合物的特殊结构对复合物性能的影响,实验结果表明,Fe2O3/MCNF复合物电极表现出优异的电化学性能,这是由于:样品的介孔孔道能够为Fe2O3纳米粒子的体积变化提供缓冲的空间;相互连通的孔道有利于Fe2O3与电解液充分接触。采用相同的方法制备了Fe2O3/carbon foam复合材料,研究了其电化学性能,并与Fe2O3/MCNF复合材料进行了对比。(4)采用热剥离GO的方法制备了官能团含量不同的两种功能化石墨烯:FGS300和FGS900,采用简单的水热合成,在没有任何添加剂的情况下,仅利用Sn Cl4·5H2O的水解制备了Sn O2/FGS复合物,研究了其电化学储锂性能,并讨论了官能团对产物性能的影响。实验结果表明,Sn O2/FGS900复合物电极在较小的电流密度下能够表现出较好的电化学性能,而当在大电流密度下进行循环测试时,Sn O2/FGS300却能表现出更好的电化学性能。通过低温熔融-水解-煅烧的方法来制备Sn O2/MCNF复合物,并研究了其电化学性能。测试结果显示,复合物保持了MCNF的双介孔结构,并表现出良好的循环性能。
[Abstract]:Lithium ion batteries have the characteristics of high open circuit voltage, low self discharge rate, long cycle life, high specific energy and no memory effect. It is known as the green energy and leading power in twenty-first Century. The performance of lithium ion batteries depends on the structure and properties of Yu Zheng polar materials, negative electrode materials and electrolyte materials. It has been a hot topic in recent years to develop cheap and high performance positive materials. For negative materials, commercialized negative materials are mainly graphite, but the theoretical capacity of graphite is only 372 m A h/g, so it is unable to meet the needs of high energy lithium ion batteries. Therefore, a new type of negative electrode with higher capacity and safer capacity is developed. It is of great significance. Among the many negative materials, Sn O2 and Fe2O3 are two highly potential materials. But because of the poor conductivity of these oxides, and in the process of charging and discharging, with the insertion and removal of lithium ions, the Sn O2 and Fe2O3 will produce huge volume changes, resulting in the pulverization of the material and the rapid deterioration of the capacity of the materials. Reducing. How to improve the cycling performance of these oxides has also become an important topic in this field. Since carbon materials have good cycling performance and oxide materials have high specific capacity, it is possible to gain the advantages of the combination of carbon materials and oxides to make full use of the defects of the single material and to make up the defects of the two materials. Sn O2/graphene, Sn O2/FGS, Sn O2/MCNF and Fe2O3/MCNF, Fe2O3/carbon foam composites were prepared by different methods. The effects of porosity, load, current density and different carriers on the electrochemical properties of the products were studied in this paper. (1) in situ synthesis method, Sn C. L2? 2H2O is a tin source, with graphite oxide (GO) as the matrix and a weak polar ethanol as solvent. The porous structure of Sn O2/graphene composite is prepared through redox reaction between Sn2+ and graphite oxide. The existence of porous structure is beneficial to the transfer of electrolyte and the transfer of charge; the existence of graphene, on one hand, is Sn O2. A good conductive network is provided, on the other hand, the volume change of Sn O2 can be buffered. The electrochemical test results show that the composite electrode materials exhibit good electrochemical performance. (2) Sn O2/graphen is prepared by hydrothermal synthesis without adding any additives to Sn Cl2. 2H2O and GO as raw materials. The effects of the electrochemical properties of the composite with different load and the porosity of the material on the properties of the products were discussed. The results showed that the samples with higher porosity showed good electrochemical performance because the presence of micropores could provide a higher active area. The hydrothermal synthesis was carried out by microwave method. The reaction time was shortened to 2 min, and the effect of microwave reaction time on the performance of the product was studied. The results showed that when the microwave time was about 2 min, the raw material had been completely reacted and the preparation time of the complex was greatly shortened. (3) the methods described in the literature were improved and the high specific surface area of mesoporous carbon nanofibers (MCNF) arrays were prepared, M CNF has a high specific surface area, large pore volume and graphitization structure, which is a good carrier. Fe2O3/MCNF composites are prepared by thermal decomposition of nitrate at low temperature. The electrochemical properties of the composites as anode materials for lithium ion batteries are studied. The effects of the special structure of the complex on the properties of the composites are discussed. The results show that the Fe2O3/MCNF composite electrode shows excellent electrochemical performance, because the mesoporous channel of the sample can provide a buffer space for the volume change of Fe2O3 nanoparticles, and the interconnected channel is beneficial to the full contact between the Fe2O3 and the electrolyte. The same method is used to prepare the Fe2O3/carbon foam composite. The electrochemical properties were compared with the Fe2O3/MCNF composites. (4) two functional fossils of functional groups were prepared by thermal stripping GO: FGS300 and FGS900, using simple hydrothermal synthesis, and in the absence of any additives, the Sn O2/FGS complex was prepared by the hydrolysis of Sn Cl4. 5H2O only. The effect of functional group on the performance of the product is discussed. The experimental results show that the Sn O2/FGS900 composite electrode can show good electrochemical performance at a small current density, while Sn O2/ FGS300 can show better electrochemical performance when the current density is measured at a large current density. The Sn O2/MCNF complex was prepared by the method of temperature melting hydrolysis calcination, and its electrochemical properties were studied. The results showed that the compound retained the double mesoporous structure of MCNF and showed good cycling performance.
【学位授予单位】：南京航空航天大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM912

【参考文献】