耐高电压锂离子电池电解液的开发研究
发布时间：2018-07-26 14:42
【摘要】：电解液是锂离子电池不可或缺的一部分，在很大程度上制约着电池的安全性和稳定性。现今，人们对电池的能量密度需求越来越高，出现了以LiNi0.5Mn1.5O4为代表的一系列高电压正极材料，因此，耐高压电解液的研究受到了越来越广泛的关注。尽管有一些关于新型高压电解液溶剂和添加剂的研究报道，但是离商业化应用尚有较大差距。 本论文中，通过对丁二腈和己二腈的电化学窗口和离子电导率进行综合对比，确认在碳酸酯中加入5%的量使得混合电解液的物理性能最优，充放电测试研究了正极材料LiNi0.5Mn1.5O4在电解液中的性能，但循环性能不佳；向混合电解液中加入适量的双乙二酸硼酸锂能使电解液的性能得到很好的改善，2C倍率下，经过200次循环后，容量仅衰减了11%。 本文还研究了在普通电解液中添加质量分数为3%的丁二酸酐，LiNi0.5Mn1.5O4正极在该电解液中的循环稳定性能得到很大的提高，0.2C的首次放电比容量为124.5mAh g-1，在充放电电压为3.0-4.9V的区间内，1C和2C倍率循环200圈的容量维持率分别为90%和92%，而使用普通电解液时，容量维持率仅为48%和47%。 研究了丁二酸酐的作用机理，通过线性伏安扫描测试得到丁二酸酐的氧化电位要低于碳酸酯的氧化电位，说明电池在充放电的过程中，丁二酸酐优先发生氧化分解，在正极材料表面形成良好的界面膜，一方面隔绝电解液与正极材料之间的接触，减少它们之间的副反应；另一方面可以提高材料的电导率，，有利于锂离子的脱嵌和嵌入，从而提高高压正极材料的循环稳定性。 本文还考察了其他三类添加剂在高压电解液中的应用。通过循环稳定性的测试发现，加入1%的邻苯二甲酸酐后，Li/LiNi0.5Mn1.5O4电池的大倍率性能很好，循环200圈容量几乎没有衰减，其作用机理还有待进一步的研究。尝试用氟代碳酸乙烯酯取代碳酸乙烯酯，与丁二腈进行共混，所得到的混合电解液拥有高达5V的电化学稳定窗口，但遗憾的是氟代碳酸乙烯酯没有起到改善丁二腈与正极材料之间的相容性，导致LiNi0.5Mn1.5O4材料的循环性能仍然很差，猜想可能是加入的量过多或过少的原因，有待进一步的实验探索。
[Abstract]:Electrolyte is an indispensable part of lithium ion battery, which restricts the safety and stability of battery to a great extent. Nowadays, the demand for energy density of battery is more and more high, and a series of high voltage cathode materials, represented by LiNi0.5Mn1.5O4, have appeared. Therefore, the research of high voltage electrolyte has been paid more and more attention. Although there are some research reports on solvent and additive of new high voltage electrolyte, there is still a big gap from commercial application. In this paper, by comparing the electrochemical window and ionic conductivity of succinonitrile and adiponitrile, it is confirmed that the physical properties of the mixed electrolyte can be optimized by adding 5% of carbonic acid ester. The performance of cathode material LiNi0.5Mn1.5O4 in electrolyte was studied by charge-discharge test, but the cycling performance was not good. Adding proper amount of lithium diacetate borate to the mixed electrolyte could improve the performance of the electrolyte at the rate of 2C. After 200 cycles, the performance of the electrolyte was improved. Capacity only attenuates by 11. In addition, the cyclic stability of LiNi0.5Mn1.5O4 positive electrode in ordinary electrolyte was studied. The initial discharge specific capacity of 0.2C is 124.5mAh g-1, and the charge / discharge voltage is 3.0-4.9 V. The capacity maintenance rates of 1C and 2C cycles in the interval are 90% and 92%, respectively, when ordinary electrolytes are used, The capacity maintenance rate was only 48% and 47%. The action mechanism of succinic anhydride was studied. The oxidation potential of succinic anhydride was lower than that of carbonate by linear voltammetry. A good interfacial film is formed on the surface of the cathode material. On the one hand, the contact between the electrolyte and the cathode material is isolated and the side reactions between them are reduced; on the other hand, the conductivity of the material can be increased, which is favorable to the deintercalation and embedding of the lithium ion. Thus, the cyclic stability of high pressure cathode materials is improved. The application of other three kinds of additives in high-voltage electrolyte was also investigated. By testing the cycle stability, it is found that after adding 1% phthalic anhydride, the high rate performance of Li / LiNi0.5Mn1.5O4 battery is very good, and the cycle capacity of 200 cycles hardly attenuates, and the mechanism of its action remains to be further studied. Ethylfluorocarbonate was used to replace ethylene carbonate and mixed with butylene nitrile. The mixed electrolyte has a electrochemical stabilization window of up to 5 V. However, it is regrettable that ethylfluorocarbonate has not improved the compatibility between butylonitrile and cathode materials, which leads to the poor cycling performance of LiNi0.5Mn1.5O4 materials. It is suspected that the addition of too much or too little may be the reason for further experimental exploration.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912
本文编号：2146343
[Abstract]:Electrolyte is an indispensable part of lithium ion battery, which restricts the safety and stability of battery to a great extent. Nowadays, the demand for energy density of battery is more and more high, and a series of high voltage cathode materials, represented by LiNi0.5Mn1.5O4, have appeared. Therefore, the research of high voltage electrolyte has been paid more and more attention. Although there are some research reports on solvent and additive of new high voltage electrolyte, there is still a big gap from commercial application. In this paper, by comparing the electrochemical window and ionic conductivity of succinonitrile and adiponitrile, it is confirmed that the physical properties of the mixed electrolyte can be optimized by adding 5% of carbonic acid ester. The performance of cathode material LiNi0.5Mn1.5O4 in electrolyte was studied by charge-discharge test, but the cycling performance was not good. Adding proper amount of lithium diacetate borate to the mixed electrolyte could improve the performance of the electrolyte at the rate of 2C. After 200 cycles, the performance of the electrolyte was improved. Capacity only attenuates by 11. In addition, the cyclic stability of LiNi0.5Mn1.5O4 positive electrode in ordinary electrolyte was studied. The initial discharge specific capacity of 0.2C is 124.5mAh g-1, and the charge / discharge voltage is 3.0-4.9 V. The capacity maintenance rates of 1C and 2C cycles in the interval are 90% and 92%, respectively, when ordinary electrolytes are used, The capacity maintenance rate was only 48% and 47%. The action mechanism of succinic anhydride was studied. The oxidation potential of succinic anhydride was lower than that of carbonate by linear voltammetry. A good interfacial film is formed on the surface of the cathode material. On the one hand, the contact between the electrolyte and the cathode material is isolated and the side reactions between them are reduced; on the other hand, the conductivity of the material can be increased, which is favorable to the deintercalation and embedding of the lithium ion. Thus, the cyclic stability of high pressure cathode materials is improved. The application of other three kinds of additives in high-voltage electrolyte was also investigated. By testing the cycle stability, it is found that after adding 1% phthalic anhydride, the high rate performance of Li / LiNi0.5Mn1.5O4 battery is very good, and the cycle capacity of 200 cycles hardly attenuates, and the mechanism of its action remains to be further studied. Ethylfluorocarbonate was used to replace ethylene carbonate and mixed with butylene nitrile. The mixed electrolyte has a electrochemical stabilization window of up to 5 V. However, it is regrettable that ethylfluorocarbonate has not improved the compatibility between butylonitrile and cathode materials, which leads to the poor cycling performance of LiNi0.5Mn1.5O4 materials. It is suspected that the addition of too much or too little may be the reason for further experimental exploration.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912
【共引文献】
相关博士学位论文 前10条
1 廖友好;锂离子电池安全型电解质的制备及性能研究[D];华南理工大学;2013年
2 刘建生;锂离子电池新型凝胶聚合物电解质的改性研究[D];华南理工大学;2013年
3 吴贤文;功能电解液对LiMn_2O_4和LiNi_(0.5)Mn_(1.5)O_4电化学性能改善及其机理研究[D];中南大学;2013年
4 文志刚;金属氧化物微/纳米结构的合成、表征及其在锂离子电池中的应用研究[D];中南大学;2013年
5 夏阳;生物模板法构筑多级多孔结构电极材料及其储锂性能研究[D];浙江工业大学;2013年
6 裴启飞;AlCl_3-BMIC离子液体电解精炼铝中杂质行为研究[D];昆明理工大学;2012年
7 柳志民;高性能钛氧化物负极材料制备及其电化学性能研究[D];哈尔滨工业大学;2012年
8 李娜;高功率柔性锂离子电池电极材料的制备及其性能研究[D];中国科学技术大学;2013年
9 陈立锋;碳基复合材料的设计、规模化制备及其在超级电容器中的应用[D];中国科学技术大学;2013年
10 郑立炎;电致化学发光新材料的研究[D];福州大学;2011年
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