Synthesis of Novel Fluorine-Free Salts for Battery Electrolytes

Doctoral thesis, 2019

Nowadays lithium-ion batteries (LIBs) are the dominant power sources of portable electronic devices such as mobile phones, laptops and cameras. Although recently their applications have extended to areas of electromobility and hybridization of vehicle, cost and safety issues remain as big obstacles for a smoother implementation. One particularly problematic aspect of conventional LIBs is the electrolytes which typically composed of fluorinated lithium salts (e.g. LiPF6) and organic solvents. While the former is meta-stable at room temperature, quite expensive to synthesis and unsafe in the presence of moisture, the latter have high vapor pressure and are also flammable. Therefore, design and development of more stable salts and electrolytes are highly desirable, especially in the light of increased use of battery technology in e.g. electric vehicles (EVs).

In order to mitigate the challenges with the current fluorine containing electrolytes, a concerted effort was set out on the synthesis and evaluation of a new class of fluorine-free lithium and sodium salts based on pseudo-delocalized concept. Four different electrolyte concepts include: aqueous, solid state, water-in-bisalt (WiBS) and ionic liquid based, containing these anions were proposed for lithium-ion and sodium-ion batteries for the first time.

In this thesis, ten novel non-fluorinated lithium and sodium electrolyte salts based on pyridinium and ammonium pseudo-delocalized concept were synthesized and fully characterized by analytical methods such as NMR, mass spectroscopy and elemental analysis. Further, it was also attempted to present the applied synthetic methods for other pseudo-delocalized anions based on imidazolium and ammonium salts and highlight the challenges and limitations which persist during the synthesis processes of these salts.