We synthesized a series of imidazolium cations containing covalently-bound
anionic sites, such as sulfonate or sulfonamide groups. These zwitterionic
imidazolium salts were found to form molten salts just like ordinary imidazolium
salts. However, regardless of the high ion density, these ions cannot migrate
along potential gradients induced in the bulk. This is a new and unique characteristic
in molten salts. When other salts were added to this, the ions generated from
the newly added salts were able to behave as carrier ions. The ionic conductivity
of a pure molten salt was 10−9 S cm−1
at 25 °C, but jumped to 10−5 S cm−1
by adding an equimolar amount of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)
at 50 °C. The zwitterionic salt having a sulfonamide group instead
of sulfonate had an ionic conductivity of 10−4 S cm−1
at 50 °C after adding an equimolar amount of LiTFSI. These zwitterionic
imidazolium salts having vinyl groups were synthesized and polymerized. In
spite of their rubber-like properties they showed excellent ionic conductivities
of around 10−5 S cm−1 at 50 °C
following the addition of an equimolar amount of LiTFSI to the imidazolium
cation unit.
我们合成了一系列含有共价结合阴离子位点的
咪唑阳离子,例如
磺酸盐或磺酰胺基团。这些两亲性
咪唑盐被发现能够像普通的
咪唑盐一样形成熔融盐。然而,尽管离子密度很高,这些离子却无法沿着在体内诱导的电势梯度迁移。这是熔融盐中的一个新颖且独特的特性。当其他盐添加到其中时,新加入盐生成的离子能够作为载流子离子。纯熔融盐在25°C时的离子导电率为10^-9 S cm^-1,但在50°C时通过添加当量的
锂双(三
氟甲磺酰)
亚胺(LiTFSI)后跳升至10^-5 S cm^-1。含有磺酰胺基团而不是
磺酸盐的两亲性盐在加入当量的LiTFSI后,在50°C时的离子导电率为10^-4 S cm^-1。这些含有
乙烯基基团的两亲性
咪唑盐被合成并聚合。尽管它们具有类似橡胶的特性,但在向
咪唑阳离子单元添加当量的LiTFSI后,它们在50°C时显示出约10^-5 S cm^-1的优秀离子导电率。