Scavenging of Superoxide Radical Anion by Fluorinated Organosilicon Additives

Abstract

We have explored a set of structurally related fluorinated and non-fluorinated organosilicon additives and quantified their rates of reaction with the superoxide radical anion O2 •−. using rapid-scan cyclic voltammetry. Absolute reaction rate measurements in acetonitrile solvent show that O2 •− reacts with the fluorinated OS compounds with bimolecular rate constants k BM more than 1000x larger than k BM for the reaction between O2 •− and ethylene carbonate. We further identified the products of reaction of a model OS compound using multiple nuclear magnetic resonance (NMR) methods and with gas chromatography/mass spectroscopy. Chemical analysis measurements show that addition of potassium superoxide KO2 to a model fluorinated OS compound produces only one product. Our results indicate that that OS compounds improve battery performance by rapidly scavenging O2 •− in a way that produces a stable product and reduces or eliminates the competing chemical pathways associated with carbonate breakdown. These results provide new insights into how chemical structure impacts critical chemical reactions and may guide the design of new additives that further improve battery safety and stability.