新型室温熔盐二(三氟甲基磺酸酰)亚胺锂-乙酰胺体系的谱学研究

Spectroscopic Investigation of New Room-temperature Molten Salt Based on LiTFSI with Acetamide

从分析二(三氟甲基磺酸酰)亚胺锂(LiTFSI)与乙酰胺形成熔盐的作用机制出发,通过红外和拉曼光谱的谱学分析并应用非局部密度泛函方法进行量化计算来对二者的相互作用进行了讨论.发现乙酰胺通过Li—O键与LiTFSI中Li+配位而破坏了LiTFSI的离子键,形成很大的配位阳离子,且正电荷被屏蔽在乙酰胺分子中;而TFSI-离子中电荷的部分离域导致电荷被终端—CF3基团屏蔽在整个分子中,这样两个大的阴阳离子间的库伦作用很弱;同时Li—O配位也导致乙酰胺分子间的氢键断裂,因而室温下体系以液体状态稳定存在.

New room-temperature molten salt based on lithium bis （trifluoro methane sucfone） imide （LiTFSI） and acetamide with a proper molar ratio has an excellent thermal stability and electrochemical performance. The action mechanism was studied by FTIR spectroscopy, FT-Raman spectroscopy and quantum chemistry calculation with nonlocal DFT. The vibrational spectra and calculated results show that acetamide can coordinate with Li＋ cation in LiTFSI through Li-O bonding, and electrovalent bonding of LiTFSI was destroyed. A big coordinate cation formed and its positive charge was shielded in acetamide molecule. Charges of TFSI^- ion were partly off resulting in to shielding of charges in the whole molecule by the terminal CF3 group. The coulombic forces was very weakly between the cations and anions, and the coordination of Li-O can also cause the breakage of hydrogen bonding between acetamide molecules, resuiting in the formation of this molten salt in the liquid state.