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

Abstract

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.

A Desolvated Solid–Solid Interface for a High‐Capacitance Electric Double Layer

“…A roughened gold electrode was used as the working electrode, coupled with a lithium plate as the counter/reference electrode. [20] This confirmed the formation of PEC layer when the cell in E2 was discharged to 1.5 V. The results were further explored by Fourier-transform infrared spectroscopy (FT-IR). Both in E1 and E2, the electrodes at 3 V show the same vibrational spectra, which are corresponding to solvent species (Figure 2a,b).…”

Poly(ethylene oxide)-lithium difluoro(oxalato)borate new solid polymer electrolytes: ion–polymer interaction, structural, thermal, and ionic conductivity studies

“…By comparing the peak assignments of LiDFOB with LiBOB, many of the vibrational bands were shared due to a common oxalate group. The DFOB¯anion displayed out-ofphase valence vibration at 1761 cm −1 , as well as an in-phase valence vibration at 1794 cm −1 , corresponding to C═O vibrations [28]. It is also observed that the peak intensity gradually increased with the increase of LiDFOB salt in polymer-salt complex.…”

Solvate Structures and Spectroscopic Characterization of LiTFSI Electrolytes

“…A more descriptive classification than for simpler anionssuch as BF 4 − and ClO 4 − which are not flexible and thus have only a single conformation resulting in fewer modes of Li + cation coordination 1−3 is therefore necessary for Li + cation coordination by the TFSI − anion (Chart 1): SSIP uncoordinated anion CIP-I 1 anion O coordinated to 1 Li + CIP-II 2 anion O coordinated to 1 Li + AGG-Ia 2 anion O coordinated to 2 Li + AGG-Ib 3 anion O coordinated to 2 Li + AGG-IIa 3 anion O coordinated to 3 Li + AGG-IIb 4 anion O coordinated to 3 Li + AGG-III 4 anion O coordinated to 4+ Li + As part of the present evaluation, different crystalline solvates were prepared and analyzed based upon this classification. The results reported here make it clear that a rigorous deconvolution of specific forms of TFSI − ···Li + cation coordination for electrolyte liquid mixtures is a difficult challenge.…”