【作者】 房少华；

【导师】 杨立；

【作者基本信息】 上海交通大学 ， 应用化学， 2009， 博士

【摘要】 离子液体具有一系列独特的性质,包括不易挥发、不易燃、好的热稳定性、好的化学和电化学稳定性和高的离子电导率,众多研究者对其都产生了浓厚的兴趣。在本论文中,首先制备了不对称三烷基锍类、胍类和含功能团胍类三大系列新型离子液体,并研究了这些离子液体的物理及电化学性质,包括熔点、热稳定性、粘度、电导率和电化学窗口;又将两种胍阳离子离子液体和一种含醚基功能团胍阳离子离子液体作为新型电解质应用于锂二次电池中。制备出9种新的二(三氟甲基磺酰)亚胺不对称三烷基锍阳离子离子液体,并对它们的物理及电化学性能进行了研究。所有离子液体在室温下都为液态,在这些憎水性离子液体中,部分离子液体显示出低粘度和低熔点的特性。S223TFSI、S221TFSI和S123TFSI在25℃时粘度分别为33、36和39 mPa s。离子液体粘度与温度的关系在所研究的温度范围内(25-80℃)符合Arrhenius模型。离子液体的热分解温度在275-315℃的范围之内轻微地变化;它们的电化学稳定性和热稳定性使其有希望成为可应用在电化学器件中的电解质。制备出16种新的以二(三氟甲基磺酰)亚胺为阴离子的小尺寸胍阳离子离子液体,并对它们的物理及电化学性能进行了研究。离子液体的热分解温度在380-425℃的范围之内轻微地变化。其中12种离子液体在室温下都为液态,cg12TFSI、cg22TFSI和cg13TFSI在25℃时粘度分别为46、45和52 mPa s。12种离子液体的粘度、电导率与温度的关系在所研究的温度范围内(25-80℃)符合VTF模型。9种阳离子不含环状结构的离子液体与三种阳离子中含环状结构的离子液体相比,具有更好的电化学稳定性;1g23TFSI和1g33TFSI的电化学窗口最宽,其值为4.3 V(25℃)。合成出8种由含醚基功能团(甲基乙基醚基)或酯基功能团(乙酸甲酯基)的胍阳离子和TFSI-阴离子组成的离子液体,并对它们的物理及电化学性能进行了研究。所有离子液体在室温下都为液态,它们都具有低的熔点。4种含酯基功能团的胍阳离子离子液体的热分解温度在380-425℃的范围之内,明显低于其他4种含醚基功能团的胍阳离子离子液体。cg1(2o1)TFSI和cg2(2o1)TFSI的25℃时粘度分别为46和48 mPa s。离子液体的粘度、电导率与温度的关系在所研究的温度范围内(25-80℃)符合VTF模型。醚基或酯基功能团的引入并没有明显改变胍阳离子离子液体的电化学稳定性,其中1g1ETFSI的电化学窗口最宽(25℃时4.4 V)。两种胍阳离子离子液体(1g13TFSI和1g22TFSI)被选择作为新的电解质应用在锂二次电池中。这两种离子液体的还原电位约为0.7 V vs. Li/Li+,然而在无添加剂的含0.3 mol kg-1 LiTFSI的两种离子液体电解质中,被观察到在镍工作电极表面有锂沉积和溶解。这两种离子液体电解质的Li/LiCoO2电池,在0.2 C的充放电倍率下,具有好的容量和循环性能。随着倍率从0.2 C增加到1.0 C,两种离子液体电解质的放电容量明显降低。一种含醚基功能团的胍阳离子离子液体(1g1(2o1)TFSI)被选择作为新的电解质应用在锂二次电池中。含有不同浓度LiTFSI的离子液体电解质的粘度和电导率被研究。尽管这种离子液体的还原电位约为0.7 V vs. Li/Li+,在不同浓度LiTFSI的离子液体电解质中,被观察到在镍工作电极表面有锂沉积和溶解。利用锂金属对称电池的交流阻抗测试,研究锂金属与离子液体电解质的界面。在0.2 C的充放电倍率下,锂盐的浓度对该离子液体电解质的Li/LiCoO2电池的容量和循环性能有明显的影响。随着倍率从0.2 C增加到1.5 C,离子液体电解质的放电容量降低,含0.75 mol kg-1 LiTFSI的电解质具有较好的倍率性能。更多还原

【Abstract】 Ionic liquids (ILs) have attracted great interests of many researchers due to their unique characteristics, including nonvolatility, nonflammability, good thermal stability, great chemical and electrochemical stability and high ionic conductivity. And they can be used as safety electrolytes for lithium secondary batteries. In this thesis, three serials of new asymmetrical trialkylsulfonium, guanidinium and functionalized guanidinium ILs have been prepared. And physical and electrochemical properties of these products, including melting point, thermal stability, viscosity, conductivity and electrochemical window have been investigated. Two guanidinium ILs and one ether-functionalized guanidinium IL have been used as new electrolytes for lithium secondary batteries.Nine new ILs based on small asymmetric trialkylsulfonium cations with TFSI- anion have been prepared. Physical and electrochemical properties of these products have been investigated. All the products were liquids at room temperature, and some of these hydrophobic ionic liquids showed low-viscosity and low-melting point characteristics. The viscosities of S223TFSI, S221TFSI and S123TFSI were 33, 36 and 39 mPa s at 25℃, respectively. The viscosities of these ILs were well fit by the Arrhenius model over the temperature range studied (25-80℃). The thermal decomposition temperatures of these ILs slightly changed in the range of 275-315℃. Electrochemical and thermal stabilities of these ILs permitted them to become promising electrolytes used in electrochemical devices.Sixteen new guanidinium ILs based on small cations and TFSI- anion were prepared. Physical and electrochemical properties of these products have been investigated. Twelve products were liquids at room temperature. The thermal decomposition temperatures of these products slightly changed in the range of 380-425 oC. The viscosities of cg22TFSI, cg12TFSI and cg13TFSI were 45, 46 and 52 mPa s at 25℃, respectively. The viscosities and conductivities of the twelve ILs were well fit by the VTF model over the temperature range studied (25-80℃). Nine guanidinium ILs without cyclic structure had better electrochemical stability than three ILs with cyclic structure. 1g23TFSI and 1g33TFSI had the widest electrochemical windows (4.3 V at 25℃).Eight new functionalized guanidinium ILs based on small cations containing ether group (methoxyethyl group) or ester group (methyl acetate goup) and TFSI- anion have been synthesized. Physical and electrochemical properties of these products have been investigated. All the products were liquids at room temperature, and they had low melting points. The thermal decomposition temperatures of the 4 ILs with ester group were in the range of 300-345℃, which were obviously lower than the other 4 guanidinium ILs with ether group. The viscosities of cg1(2o1)TFSI and cg2(2o1)TFSI were 46 and 48 mPa s at 25℃, respectively. The viscosities and conductivities of these ILs were well fit by the VTF model over the temperature range studied (25-80℃). The ether and ester group could not remarkably affect the electrochemical stability, and 1g1ETFSI had the widest electrochemical window (4.4 V at 25℃).Two ILs based on guanidinium cations and TFSI- anion (1g13TFSI and 1g22TFSI)were chosen to be used in lithium secondary batteries as new electrolytes. The cathodic limiting potentials of the two ILs were 0.7 V versus Li/Li+. However, the lithium plating and striping on Ni electrode could been observed in the two IL electrolytes containing 0.3 mol kg-1 of LiTFSI without additive. Li/LiCoO2 cells using the two IL electrolytes without additive showed good capacity and cycle property at the current rate of 0.2 C. Discharge capacity for the two IL electrolytes decreased obviously with the increasing of the current rate from 0.2 C to 1.0 C.One IL based on ether-functionalized guanidinium cations and TFSI- anion (1g1(2o1)TFSI) were chosen to be used in lithium secondary batteries as new electrolyte. The viscosity and conductivity of IL electrolytes with different concentrations of LiTFSI have been investigated. Although the cathodic limiting potentials of this ILs were 0.7 V versus Li/Li+, the lithium plating and striping on Ni electrode could been observed in these IL electrolytes with different concentrations of LiTFSI. The interfaces between lithium metal and the IL electrolytes were also investigated by impedance spectroscopy method with lithium metal symmetrical cells. The concentrations of lithium salt had obvious effect to the capacity and cycle property of Li/LiCoO2 cells using the IL electrolytes at the current rate of 0.2 C. Discharge capacity for the two IL electrolytes decreased with the increasing of the current rate from 0.2 C to 1.5 C, and the electrolyte with 0.75 mol kg-1 of LiTFSI owned better rate performance.更多还原