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Alternative TitleFunctionalized ionic liquids as new electrolyte additives for Li-ion batteries
Thesis Advisor吕兴梅 ; 张锁江
Degree Grantor中国科学院研究生院
Degree Discipline化学工程
Keyword离子液体   添加剂   电解质   聚合物膜   高压锂离子电池
Abstract离子液体由于具有一系列优于传统有机电解质的特性,是目前新型绿色电解质研究的热点。然而离子液体自身粘度大、与电极材料相容性差等缺点造成电池的倍率性能不好、容量保持率低。寻找合适离子液体作为添加剂以弥补现有有机电解质的不足将是改善电池性能的一个有效方法。本文主要研究了低粘度高稳定性的两类离子液体分别作为电解质添加剂在“Li/LiFePO4”和“Li/LiNi0.5Mn1.5O4”电池中的应用。 论文的主要研究内容和创新成果如下: (1)合成了季铵类离子液体[N2224][TFSI]及四种烯烃取代咪唑双三氟甲基磺酰亚胺([AVIm][TFSI]、[AEIm][TFSI]、[VPIm][TFSI]及[DAIm][TFSI])离子液体,通过多种手段进行结构表征、纯度分析及物性测试。 (2)[N2224][TFSI]作为添加剂应用于“Li/LiFePO4”电池,研究了离子液体电解质的循环及倍率性能。实验结果表明最佳离子液体电解质组成为0.6 mol L-1 LiTFSI-EC-DMC-[N2224][TFSI](4.5/4.5/1,质量比),0.5 C倍率下的放电比容量高达125 mAh g-1,未含离子液体添加剂的电解质放电比容量为109 mAh g-1,[N2224][TFSI]的添加大大改善了电池的倍率性能。 (3)[AVIm][TFSI]、[AEIm][TFSI]、[VPIm][TFSI]及[DAIm][TFSI]作为添加剂应用于5 V“Li/LiNi0.5Mn1.5O4”高压电池中,系统研究了离子液体电解质的循环及倍率性能,分析和讨论了离子液体与LiNi0.5Mn1.5O4电极的作用机理。结果表明添加3 wt.%离子液体[AVIm][TFSI]时,有效地改善了电池的循环及倍率性能。XPS及SEM数据表明,[AVIm][TFSI]在LiNi0.5Mn1.5O4材料表面形成了一层致密、稳定的正极聚合物保护膜,其组分为Li2CO3、LiF、LixPFy及离子液体聚合物。
Other AbstractIonic liquids (ILs) have received considerable attentions for application as potential electrolytes in recent years, which is mainly attributable to their superior properties over conventional volatile electrolytes. However, the rate performance is not satisfactory due to their high viscosity. Using ionics liquids as electrolyte additive is one of the most effective methods to overcome the inevitable limitations of traditional solvents. In this paper, [N2224][TFSI] and four functionalized ILs based on imidazolium cations with vinyl or allyl groups and TFSI-anion were synthesized as electrolyte additives for Li-ion batteries. The main contents and innovative achievements of this research are as follows, (1) [N2224][TFSI] and four functionalized ILs based on imidazolium cations with vinyl or allyl groups ([AVIm][TFSI], [AEIm][TFSI], [VPIm][TFSI] and [DAIm][TFSI]) are designed and synthesized, which physical and electrochemical properties are investigated for these ILs. (2) To evaluate the performance of [N2224][TFSI] as electrolyte additive], the charge-discharge behavior of Li/LiFePO4 half-cell containing the mix [N2224][TFSI] electrolyte has been examined. The results suggest that the optimal electrolyte is 0.6 mol L-1 LiTFSI-EC-DMC-[N2224][TFSI] (4.5/4.5/1, wt.%). The discharge capacity for the optimal ionic liquid electrolyte at the discharge rate of 0.5 C is about 125 mAh g-1, while the blank electrolyte is 109 mAh g-1. These results reveal an improving effect of [N2224][TFSI] on the rate properties of theLiFePO4 half-cell. (3) Four functionalized ILs based on imidazolium cations with vinyl or allyl groups and TFSI-anion are used as electrolyte additives for high-voltage LiNi0.5Mn1.5O4 half-cell. To evaluate the performance of additives, the charge-discharge behavior of LiNi0.5Mn1.5O4 half-cell with additives and surface chemistry of LiNi0.5Mn1.5O4 cathode were examined. Cycle life and rate performance of the Li/LiNi0.5Mn1.5O4 cells containing 3 wt.% [AVIm][TFSI] can be improved. Surface analysis of the cathode material (XPS and SEM) suggests that a stable and compact polymer film is formed on the LiNi0.5Mn1.5O4 cathode by electroinitiated polymerization of imidazolium cation with vinyl and allyl group.
Document Type学位论文
Recommended Citation
GB/T 7714
王中妮. 功能化离子液体添加剂用于锂离子电池电解质的研究[D]. 中国科学院研究生院,2013.
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