锂离子电池负极材料—低温碳化微球的制备及其改性研究

发布时间：2018-03-03 03:25

  本文选题：锂离子电池　切入点：负极材料　出处：《江西师范大学》2014年硕士论文　论文类型：学位论文

【摘要】：锂离子电池作为一种新型的化学电源，具有工作电压高、比能量大、放电电位曲线平稳、自放电小、循环寿命长、低温性能好、无记忆、无污染等突出的优点，能够满足人们对便携式电器所需要的电池小型轻量化和有利于环保的双重要求，广泛用于移动通讯、笔记本电脑等小型电子装置，也是未来电动交通工具使用的理想电源。负极材料作为锂离子电池的主要组成部分，其性能的好坏直接影响电池的性能，高容量、可靠循环性的负极材料成为人们的研究重点。石墨是目前主流的商业化锂电负极材料，但由于石墨本身结构特性的制约，石墨负极材料的发展也遇到了瓶颈，比如比容量已经到达极限、不能满足大型动力电池所要求的持续大电流放电能力等，因此人们开始把目光投向硬碳和非碳材料。而硬碳材料由于在安全和循环寿命方面显示出较好的性能，具有较强的研究意义。 低温碳化微球是一种无定形球状硬碳材料，其制备方法如下：（1）以丙烯腈为单体，经乳液聚合法制备出聚丙烯腈纳米球；（2）将聚丙烯腈纳米球经过预氧化及低温碳化等一系列处理，即可得到的一种球状硬碳材料。该过程具有制备方法简单，成本低以及环保无毒等优点，材料也具有尺寸均匀，直径范围可控，并可实现大规模工业生产。本文将自制的低温碳化微球用作锂离子电池负极材料，研究了碳化温度、导电剂的性能、碳酸钙（CaCO3）造孔、掺入碳酸锂（Li2CO3）以及纳米硅粉（Si）的掺杂等处理对碳微球电化学性能的影响。 主要研究工作如下： 1.通过控制碳微球的碳化温度(500℃-900℃)，研究碳化温度对其电化学性能的影响。结果显示，随着碳化温度的提高，碳微球的石墨化程度提高，电导率也提高。其比容量逐渐下降，循环稳定性增加。当碳化温度为600℃时，循环性能有较大的改善，首次充电容量达383.6mAh/g,经过50次循环后仍保留310mAh/g。 2.将导电炭黑、分散的碳纳米管以及碳纳米管粉末等导电剂掺入电极，研究导电剂形状及分散效果对碳微球电化学性能的影响。结果表明：棒状碳纳米管更有利于空间网络结构的形成，，首次充电比容量达到410mAh/g,表现出比383mAh/g的导电炭黑更优的性能,而分散的碳纳米管的首次充电比容量可达455mAh/g,经过50次循环后仍能保持360mAh/g。 3.利用碳酸钙(CaCO3)为模板对碳微球进行造孔，探讨形貌、比表面积以及微孔百分比对碳微球电化学性能的影响。结果显示碳化前、后刻蚀模板剂碳酸钙产生明显的效果，影响碳微球中微孔百分比。其中碳化后刻蚀的碳微球的首次充电比容量可达620mAh/g,经过50次循环后仍能保留520mAh/g,相对纯的碳微球有明显的提高。 4.通过直接法和乳液聚合法研究了碳酸锂掺入量对碳微球的电化学性能的影响。由结果可知，直接法加入碳酸锂的碳微球会在其表面及微孔内形成碳酸锂盐层，有利于SEI膜的形成，当碳酸锂量为4%时，材料的电化学性能较好，首次充电比容量可达到505mAh/g。乳液聚合掺入碳酸锂则不会覆盖微孔，但仍能在微球表面形成SEI膜。当碳酸锂的掺入量为2%（即碳酸锂在碳微球中为3.4%）时，材料的电化学性能最佳，此时首次充电容量可达到530mAh/g，其经过50次循环仍保留440mAh/g。 5.以纳米硅粉为种子，丙烯腈为单体进行种子乳液聚合制备PAN-Si复合材料，再将PAN-Si复合材料经碳化后制备碳硅复合材料，研究碳硅复合材料中硅含量对其电化学性能的影响。结果表明，随着硅含量的增加，复合材料的首次容量增加，循环性能下降，不同电流密度下表现更加明显。而当掺入硅的含量为5%（即硅占硅碳复合物7.5%）时，此时材料的综合电化学性能最好，尽管经过50次循环仍能保留570mA/g,拥有优异的循环性能，也具有较高的充电比容量。
[Abstract]:Lithium ion battery is a new type of chemical power source, has a high working voltage, high specific energy, stable discharge potential curve, small self discharge, long cycle life, low temperature performance, no memory, no pollution and other prominent advantages, can meet the need of people portable electric battery small and light and has the dual requirements for environmental protection, are widely used in mobile communications, a small electronic device for notebook computer, but also the future of electric vehicles using the ideal power. As the main part of anode materials for lithium ion battery, its performance will directly influence the performance of the high capacity battery, anode materials and reliable of the circulation has become a research focus. The graphite is the current mainstream commercial lithium ion battery anode material, but due to the restriction of structure characteristics of graphite, graphite anode material development has encountered a bottleneck, such as capacity has reached the pole The limit can not satisfy the continuous high current discharge capacity required by large power battery, so people began to focus on hard carbon and non carbon materials. Hard carbon materials have strong research significance because of their good performance in terms of safety and cycle life.
Low temperature carbonization microsphere is a kind of amorphous spherical hard carbon material, its preparation method is as follows: (1) with acrylonitrile as monomer was prepared by emulsion polymerization of polyacrylonitrile nano spheres; (2) the polyacrylonitrile nanospheres after pre oxidation and low-temperature carbonization of a series of processing, a spherical hard carbon material can be obtained to. This process has the advantages of simple preparation method, low cost and environmentally friendly non-toxic materials, with uniform size and controllable diameter range, and can realize the large-scale industrial production. The low temperature carbonization of homemade microspheres as anode material for lithium ion batteries, carbonization temperature on properties of conductive agent, calcium carbonate (CaCO3 pore,) doped lithium carbonate (Li2CO3) and nanometer silica fume (Si) effects of doping treatment on the electrochemical properties of carbon microspheres.
The main research work is as follows:
1.閫氳繃鎺у埗纰冲井鐞冪殑纰冲寲娓╁害(500鈩

本文编号：1559357