Li＋在基于N,N-二甲基甲酰胺混合溶剂中的溶剂化

利用红外和拉曼光谱技术研究了Li^＋在不同浓度、不同溶剂组成的LiBF₄/N,N-二甲基甲酰胺-乙腈、LiBF₄/N,N-二甲基甲酰胺-四氢呋喃电解质溶液中的优先溶剂化现象. 红外和拉曼光谱的分析表明, Li^＋主要与DMF分子相互作用, 导致该分子的C＝O伸缩振动谱带、N—C＝O形变谱带、CH₃摇摆谱带等发生了分裂. Li^＋与其它溶剂分子的相互作用较弱, 谱带的分裂现象并不明显. Li^＋溶剂化数的计算显示, Li^＋第一溶剂化层内DMF分子的数目一般大于2, 这说明 Li^＋在混合溶剂体系内优先与DMF分子相互作用. 量子化学计算支持了这一结论.

Solvation of Lithium Ion in N,N-Dimethylformamide-based Mixtures

Solutions of lithium tetrafluoroborate in N,N-dimethylformamide-acetonitrile and N,N-dimethyl-formamide-tetrahydrofuran mixed solvents have been investigated by infrared and Raman spectroscopies. New bands, due to Li^＋ solvation, were detected in the region of the C＝O strectching, O＝C—N deformation and CH₃ rocking modes for N,N-dimethylformamide. The change in band for the co-solvents was weak. The number of N,N-dimethylformamide molecules in the first solvation shell of Li^＋ was calculated and the preferential solvation of lithium ion by N,N-dimethylformamide indicated. This result has been supported by our ab initio calculations.