An Updated View of Primary Ionization Processes in Polar Liquids

Abstract

According to picosecond radiolysis data, primary radical cations in irradiated carbonates are very rapidly deprotonated. At the same time, analysis of the radiation-induced fluorescence from carbonate solutions indicates the formation of solvent-related radical cationic species with a relatively long lifetime. We use quantum chemical methods to develop a model of carbonate ionization that reconciles these conflicting data. Using ethylene carbonate as an example and assuming that its molecules exist in solution as a collection of dimeric associates, we show that both processes are the result of the loss of an electron from such dimers. This demonstrates that the generally accepted conceptualization of a primary ionization event, based on the idea of the formation of a radical cation of an individual molecule of an irradiated substance, requires revision in the case of polar aprotic liquids that tend to form molecular associates.

Radiolysis of Electrolytes in Batteries: A Quick and Efficient Screening Process for the Selection of Electrolyte‐Additive Formulations

“…[ 36 ] In a very recent work, quantum chemistry calculations evidenced that EC molecules exist in solution as dimers and that radical cations are formed from these dimers, and not from a single molecule, implying that EC ∙+ should be more properly labeled as EC 2 ∙+ . [ 54 ] For the sake of clarity, we will rather write EC ∙+ below, even if the writing with the dimers should be more accurate. The ring of this radical cations opens, and the ∙ OCH 2 CH 2 OC ∙+ O species is then formed.…”

In Situ Electron Paramagnetic Resonance Monitoring of Predegradation Radical Generation in a Lithium Electrolyte

“…In lithium electrolyte, EC engages in additional processes of dimerization and Li + solvation. − Figure demonstrates that the reduced dimer, (EC) 2 •– , is preferred to postreduction dimerization by 40.88 kJ/mol. Prominently, the g -factor of (EC) 2 •– remains intact (i.e., g = 2.0029) and close to g e = 2.0023 and the hfcc values are again small (Figure S7).…”