Solvate Structures and Computational/Spectroscopic Characterization of Lithium Difluoro(oxalato)borate (LiDFOB) Electrolytes

Lithium difluoro­(oxalato)­borate (LiDFOB)
is a relatively new salt
designed for battery electrolyte usage. Limited information is currently
available, however, regarding the ionic interactions of this salt
(i.e., solvate formation) when it is dissolved in aprotic solvents.
Vibrational spectroscopy is a particularly useful tool for identifying
these interactions, but only if the vibrational bands can be correctly
linked to specific forms of anion coordination. Single crystal structures
of LiDFOB solvates have therefore been used to both explore the DFOB–...Li+ cation coordination interactions
and serve as unambiguous models for the assignment of the Raman vibrational
bands. The solvate crystal structures determined include (monoglyme)2:LiDFOB, (1,2-diethoxyethane)3/2:LiDFOB, (acetonitrile)3:LiDFOB, (acetonitrile)1:LiDFOB, (dimethyl carbonate)3/2:LiDFOB, (succinonitrile)1:LiDFOB, (adiponitrile)1:LiDFOB, (PMDETA)1:LiDFOB, (CRYPT-222)2/3:LiDFOB, and (propylene carbonate)1:LiDFOB. DFT calculations
have been incorporated to provide additional insight into the origin
(i.e., vibrational modes) of the Raman vibrational bands to aid in
the interpretation of the experimental analysis.

二氟（草酸根合）硼酸锂（Lithium difluoro(oxalato)borate, LiDFOB）是一种相对新兴的电池电解质用盐类。目前针对该盐溶解于非质子溶剂时的离子相互作用（即溶剂化物形成过程）的相关信息仍较为有限。振动光谱法是识别此类相互作用的有效手段，但前提是需将振动谱带与特定形式的阴离子配位作用建立准确关联。因此，研究人员借助LiDFOB溶剂化物的单晶结构，既探究了DFOB–…Li+阳离子配位相互作用，同时也为拉曼振动谱带的归属提供了明确的参照模型。本次测定的溶剂化物晶体结构包括：(单乙二醇二甲醚)₂:LiDFOB、(1,2-二乙氧基乙烷)₃/₂:LiDFOB、(乙腈)₃:LiDFOB、(乙腈)₁:LiDFOB、(碳酸二甲酯)₃/₂:LiDFOB、(丁二腈)₁:LiDFOB、(己二腈)₁:LiDFOB、(五甲基二乙烯三胺)₁:LiDFOB、(CRYPT-222)₂/₃:LiDFOB以及(碳酸丙烯酯)₁:LiDFOB。本研究还引入了密度泛函理论（DFT）计算，以进一步阐明拉曼振动谱带的起源（即振动模式），辅助实验分析结果的解读。