TY - JOUR KW - Spectroscopic ellipsometry KW - Hydrofluoric acid KW - LiPF6 degradation KW - Lithium-ion batteries AU - Simon F Lux AU - Ivan T Lucas AU - Elad Pollak AU - Stefano Passerini AU - Martin Winter AU - Robert Kostecki AB -

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.

BT - Electrochemistry Communications DA - 01/2012 DO - 10.1016/j.elecom.2011.10.026 IS - 1 LA - eng N2 -

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.

PY - 2012 SP - 47 EP - 50 T2 - Electrochemistry Communications TI - The mechanism of HF formation in LiPF6 based organic carbonate electrolytes VL - 14 ER -