The mechanism of HF formation in LiPF6 based organic carbonate electrolytes

The mechanism of HF formation in LiPF6 based organic carbonate electrolytes

TitleThe mechanism of HF formation in LiPF6 based organic carbonate electrolytes
Publication TypeJournal Article
Year of Publication2012
AuthorsSimon F Lux, Ivan T Lucas, Elad Pollak, Stefano Passerini, Martin Winter, Robert Kostecki
JournalElectrochemistry Communications
Volume14
47
Issue1
Pagination47-50
Date Published01/2012
KeywordsHydrofluoric acid, LiPF6 degradation, Lithium ion batteries, spectroscopic ellipsometry
Abstract

Spectroscopic ellipsometry was used to study the time-dependent formation of HF upon the thermal degradation of LiPF6 at 50 °C in a lithium ion battery electrolyte containing ethylene carbonate and diethyl carbonate. The generated HF was monitored by following the etching rate of a 300 nm thick SiO2 layer, grown on both sides of a silicon wafer substrate, as a function of the immersion time in the electrolyte at 50 °C. It was found that the formation of HF starts after 70 h of exposure time and occurs following several different phases. The amount of generated HF was calculated using an empirical formula correlating the etching rate to the temperature. Combining the results of the HF formation with literature data, a simplified mechanism for the formation of the HF involving LiPF6 degradation, and a simplified catalytical reaction pathway of the formed HF and silicon dioxide are proposed to describe the kinetics of HF formation.

DOI10.1016/j.elecom.2011.10.026