Synthesis of lithium difluoro(oxalate)borate (LiODFB), phase diagram and ions coordination of LiODFB in dimethyl carbonate

A new two-step synthetic method was successfully developed to simplify the recrystallization process of lithium difluoro(oxalate)borate (LiODFB). Meanwhile, the purity of LiODFB as-prepared was determined by NMR, ICP-AES and Karl Fisher measurements, respectively. The as-prepared LiODFB presents a high purity up to 99.95%. Its metal ions and water contents are under good control as well. Besides, its structure information and thermal properties were confirmed by FTIR, Raman and DSC-TGA analyses, respectively. LiODFB exerts fine thermostability and hypo-water-sensitivity and its structure information agrees well with previous literature. Furthermore, a combination of phase diagram and Raman spectroscopy were utilized to study the thermal phase behavior and ions coordination of LiODFB-DMC binary system to optimize the synthesis and recrystallization process. Although there are three types of molecular interaction forms (CIPs, AGG-IIa, AGG-IIIb) in LiODFB-DMC binary system, LiODFB can only be isolated as large single crystal solvate as LiODFB.(DMC)(3/2) by slowly cooling subjected to the nucleation kinetics. Therefore, the fundamental information of our work is helpful in accelerating the application of LiODFB in Li-ion secondary batteries.