锂离子动力电池电解液氧化还原穿梭添加剂的研究

发布时间：2018-03-10 00:25

本文选题：氧化还原穿梭　切入点：噻蒽　出处：《复旦大学》2014年硕士论文　论文类型：学位论文

【摘要】：近几年来,氧化还原穿梭限压添加剂的研制逐渐成为锂离子蓄电池限压一致性的研发重点,该种方法具有以下几点优势：(1)可以在电池内部建立一种防过充过放的电化学自我保护机制,在发挥保护作用的过程中,不会对电池体系造成任何不可逆损害,对电池的保护作用是可恢复性的；(2)穿梭所起的电化学反应是可逆的,因此,穿梭的添加量少,使用寿命长；(3)制造工艺简单,生产成本低。目前,电池一致性问题一直限制着我公司锂离子二次电池在笔记本电脑、电动工具、电动汽车等领域中的发展,特别是在电动汽车等大型动力系统中各单体电池的电压一致性是我们迫切需要解决的问题。鉴于上述情况,我们开展了氧化还原穿梭添加剂研究,目的开发出几种可应用于实际LiFePO4/C电池体系的氧化还原穿梭添加剂。在第一阶段的研究工作中,我们探讨了氧化还原穿梭作用的动力学过程、其在石墨负极上的得失电子原理以及在实际电池组中的作用效果,初步筛选了十种4V级氧化还原穿梭添加剂,分别对其物理特性、电化学性能、限压性能及电池的常规性能进行了实验研究。对比结果表明,噻蒽具有合适的氧化还原电位,较高的分解反应速率,对电池其它电性能和安全性能没有影响,是一种优良的LiFePO4/C电池体系电解液氧化还原穿梭添加剂。在第二阶段的研究工作中,深入研究了噻蒽限压能力的发挥、衰减、恢复、受外界因素的影响程度,总结了噻蒽在一些实际电池产品中的应用结果,实验验证了噻蒽消耗后对电池常规性能的影响。研究表明噻蒽是一种适用于LiFePO4/C电池体系的氧化还原穿梭限压添加剂,可显著提高串联电池组中单体电池的一致性。通过模拟笔记本电脑长时间待机过程的实验发现,噻蒽在循环使用的过程中,损失衰减速度相对较慢,具有良好的循环使用寿命,从而使得电池组具有优异的循环性能。虽然,噻蒽的限压内能力受过充电流大小和环境温度的双重影响,但可通过提高添加剂浓度、减小极片及隔膜厚度等方法,提高氧化还原穿梭的分子扩散速率,从而改善穿梭在不同电流和温度下的限压性能。此外,噻蒽的在电池体系内的引入,不仅对电池的常规性能(特别是自放电性能)没有任何不利影响,而且,当噻蒽的限压作用消耗殆尽后,噻蒽添加剂在“氧化一还原”循环过程中产生的不可逆反应副产物,亦不会对电池的常规性能有任何不利影响。
[Abstract]:In recent years, the development of redox shuttle voltage limiting additives has gradually become the focus of research and development of the voltage limiting consistency of lithium ion batteries. This method has the following advantages: 1) it can establish an electrochemical self-protection mechanism against overcharge and overdischarge within the battery, and will not cause any irreversible damage to the battery system in the process of exerting its protective effect. The electrochemical reaction to the battery protection is recoverable. The electrochemical reaction is reversible. Therefore, the added amount of shuttle is less, the service life is long, the manufacturing process is simple, and the production cost is low. Battery consistency has been limiting the development of lithium ion secondary batteries in notebook computers, electric tools, electric vehicles, etc. Especially in large power systems such as electric vehicles, the voltage consistency of individual cells is an urgent problem that we need to solve. In view of the above situation, we have carried out a study on redox shuttle additives. Objective to develop several redox shuttle additives that can be used in practical LiFePO4/C battery systems. In the first stage of the study, we discussed the kinetic process of redox shuttling. The principle of electron gain and loss on graphite negative electrode and its effect on actual battery pack. Ten kinds of 4V redox shuttle additives were preliminarily selected, and their physical properties and electrochemical properties were studied. The experimental results show that thianthracene has a suitable redox potential and a high decomposition rate, and has no effect on other electrical and safety properties of the battery. It is an excellent oxidation-reduction shuttle additive for electrolyte of LiFePO4/C battery system. In the second stage of the research work, the exertion, attenuation, recovery and influence of external factors on the limiting capacity of thianthracene were deeply studied. The application results of thianthracene in some practical battery products are summarized, and the effect of thianthracene consumption on the conventional performance of the battery is verified. The results show that thianthracene is a kind of redox shuttle limiting voltage additive suitable for LiFePO4/C battery system. By simulating the long standby process of notebook computer, it is found that the loss attenuation rate of thianthracene is relatively slow, and it has a good cycle life. Although the pressure limiting capacity of thianthracene is influenced by the charge current size and ambient temperature, it can be reduced by increasing the concentration of additives, reducing the thickness of the electrode and diaphragm, etc. Increase the molecular diffusion rate of the redox shuttle, thus improving the voltage limiting performance of the shuttle at different current and temperature. In addition, the introduction of thianthracene in the battery system, Not only does it have no adverse effect on the conventional performance (especially self-discharge performance) of the battery, but also, when the pressure limiting effect of thianthracene is exhausted, the by-product of the irreversible reaction produced by the thianthracene additive during the "oxidation-reduction" cycle, Nor will there be any adverse effect on the conventional performance of the battery.
【学位授予单位】：复旦大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

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