Quantification of PF5 and POF3 from Side Reactions of LiPF6 in Li-Ion Batteries

By S. Solchenbach, Michael Metzger, Masamitsu Egawa, Hans Beyer, H. Gasteiger. 2018

146 citations recorded by the source corpus.

The electrochemical oxidation of LiPF 6 -based electrolytes is reported to generate POF 3 gas. In order to enable a quantitative analysis of the LiPF 6 decomposition reactions, we aimed to establish calibration factors for POF 3 and PF 5 in on-line electrochemical mass spectrometry (OEMS). Thermal decomposition of dry LiPF 6 is expected to yield PF 5 , but instead all PF 5 is detected as POF 3 in our OEMS setup, rendering a differentiation of the two gases impossible and presenting an artefact which likely occurs with most on-line mass spectrometry systems due to the high reactivity of PF 5 . However, we can still determine a cumulative calibration factor for POF 3 + PF 5 (referred to as “POF 3 ”), which is then used to investigate the evolution of gases during the oxidation of an EC/LiPF 6 electrolyte on a carbon black electrode. Mechanistic experiments with protons or water added to EC/LiPF 6 electrolyte show that protons trigger the formation of PF 5 , while the kinetics for the hydrolysis of LiPF 6 with water at room temperature are too slow to be detectable. These findings let us conclude that the oxidation of EC generates highly acidic species, which cause the decomposition of PF 6 − to PF 5 and HF; the PF 5 is then detected as POF 3 in the OEMS.

Subfields: Automotive Engineering, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/aaef3c07954a75dbbdd489032652d55a8ce7f951

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