Influence of the Fluorination Degree of Organophosphates on Flammability and Electrochemical Performance in Lithium Ion Batteries: Studies on Fluorinated Compounds Deriving from Triethyl Phosphate

Murmann P, Moennighoff X, von Aspern N, Janssen P, Kalinovich N, Shevchuk M, Kazakova O, Roeschenthaler G-V, Cekic-Laskovic I, Winter M

Research article (journal)

Abstract

Three symmetric substances originating from triethyl phosphate were specifically synthesized with varying degree of fluorinationat the side chain. Different concentrations of each phosphate were evaluated as co-solvent with regard to their flammability and theelectrochemical cycling performance.With higher degree of fluorination and a higher amount of the phosphate in the electrolyte, theself-extinguishing time (SET), a value to determine and compare the flammability of electrolytes, could be significantly lowered toyield a non-flammable electrolyte mixture. A specifically designed SET device is introduced, which offers more accurate results dueto lowered standard deviations by minimizing random and systematic errors. As the application of phosphates as co-solvents resultsin a trade-off in cycling performance, a thorough determination in regard to the ionic conductivity, the anodic oxidation stabilityand the compatibility with anode and cathode material was carried out in half- and full-cells. The manuscript strives to establish adeeper understanding of the influence that the utilization of phosphates as co-solvents entail with special focus on the fluorinationdegree. It could be shown that the partially fluorinated phosphate offers the best cycling results and therefore the lowest trade-off inperformance, while a severe improvement in SET could be achieved compared to the reference electrolyte.

Details zur Publikation

Release year: 2016
Language in which the publication is written: English