氟气氟化含氢氟聚醚制备双端羟基全氟聚醚

Preparation of double-terminated hydroxyl perfluoropolyether from hydrofluoropolyether fluorinated by fluorine gas

以含氢氟聚醚(E10H)为原料,利用氟氮混合气进行氟化制备了双端羟基全氟聚醚(F-E10H-AL),分别探索了常温氟化、低温氟化及先低温后常温氟化的3种氟化工艺;然后,与双三氟甲烷磺酸亚胺锂(LiTFSI)制备成锂离子电解质(F-E10H-AL/LiTFSI)。采用红外光谱、核磁共振氢谱和氟谱分析氟化后产物结构,并采用电化学工作站测试其阻抗和计时电流。结果表明,低温氟化工艺具有较高的氟化效率,在–10℃对E10H直接氟化12h后,分子链上有21.0%的H被F取代,但会产生较多的封端基团CF_(3)O—。当利用六氟环氧丙烷二聚体酯化保护E10H上的羟基时,采用先低温后常温氟化工艺,分子链上有48.3%的H被F取代;最后,将氟化产物还原得到F-E10H-AL,分子链末端基本没有CF_(3)O—。结合阻抗和计时电流的数据,计算出锂离子电解质的离子迁移数为0.32,高于商业化双端羟基全氟聚醚(Z-DOL)/LiTFSI的锂离子迁移数(0.07)。

Double-terminated hydroxyl perfluoropolyether(F-E10H-AL) was prepared by fluorination reaction of hydrofluoropolyether(E10H) in the presence of a mixture of fluorine and nitrogen. Three fluorination processes were explored, including normal temperature fluorination, low temperature fluorination, and first low temperature and then normal temperature fluorination. Then, lithium-ion electrolyte(F-E10HAL/Li TFSI) was prepared by combining with lithium bis(trifluoromethanesulphonyl)imide(LiTFSI). The structure of the fluorinated product was characterized by infrared spectroscopy, hydrogen and fluorine nuclear magnetic spectroscopies. The impedance and chronoamperometry of F-E10H-AL/LiTFSI were tested by electrochemical workstation. The results showed that the low-temperature fluorination process exhibited high fluorination efficiency. After direct fluorination of E10H at –10 ℃ for 12 h, 21.0% H atoms in the molecular chain was replaced by F atoms, but more capping group CF_(3)O— could be produced. While the hydroxyl group on E10H was protected by hexafluoropropylene oxide dimer, the fluorination process of low temperature followed by normal temperature was adopted, and 48.3% H atoms in the molecular chain were replaced by F atoms. Finally, the fluorinated product was reduced to obtain F-E10H-AL, and the end of the molecular chain was almost without CF_(3)O—. Combining the impedance and chronoamperometry data, the lithium ion transference number of F-E10H-AL/LiTFSI was calculated to be 0.32, which was higher than that of commercial double-terminated hydroxyl perfluoropolyther(Z-DOL)/LiTFSI(0.07).