Borate esters with different lengths of ethyleneoxy units were investigated as electrolyte solvents for lithium salts such as lithium triflate, perchlorate, bis(trifluoromethanesulfonyl)imide, bis(pentafluoroethanesulfonyl)imide and bis(oxalato)borate. The ionic conductivity of the salt solutions was measured to be of the order of 10−3 to 10−4 S cm−1 at room temperature. Transference number measurements for the borate ester–lithium perchlorate system indicated roughly equal contributions of cations and anions to the total conductivity, while the borate ester–lithium bis(oxalato)borate showed predominant anionic conductivity. Nanocomposite electrolytes were prepared by heterogeneous doping of the borate esters with silica. Composites with 10 nm silica particles exhibited low-viscous electrolyte behavior with a clear but modest conductivity enhancement at very low volume fractions of silica and a depression of the conductivity value at higher volume fractions. In the case of fumed silica (7 nm) the nanocomposites had at a sufficiently high volume fraction and a jelly, transparent appearance with the favorable mechanical properties of a high-viscous semi-solid without noteworthy decrease in the Li ion conductivity. In particular the last material with its combination of favourable electrical, mechanical and optical properties, promises to be a viable candidate for various applications (Li-based batteries, solar cells).
研究了不同长度的
乙烯氧基单位的
硼酸酯作为
锂盐(如三
氟甲烷磺酸锂、
过氯酸锂、双( trifluoromethanesulfonyl)
亚胺、双( pentafluoroethanesulfonyl)
亚胺和双(
草酸)
硼酸盐)的电解质溶剂。在室温下,盐溶液的离子导电率测得为10−3到10−4 S cm−1量级。
硼酸酯-
过氯酸锂体系的传输数测量结果表明,阳离子和阴离子对总导电率的贡献大致相等,而
硼酸酯-双(
草酸)
硼酸锂则显示出以阴离子导电为主。通过用
二氧化硅进行异质掺杂制备了纳米复合电解质。掺杂10 nm
二氧化硅颗粒的复合材料表现出低粘度电解质特性,在非常低的
二氧化硅体积分数下有明显但适度的导电性增强,而在较高体积分数下导电率则降低。在气相
二氧化硅(7 nm)的情况下,纳米复合材料在足够高的体积分数下呈现出果冻状的透明外观,并具备高粘度半固体的良好机械性能,同时
锂离子导电率没有明显下降。特别是最后一种材料由于其良好的电学、机械和光学性能,承诺成为各种应用(
锂电池、太阳能电池)的可行候选材料。