Publications by authors named "Dennis R Gallus"

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Impact of Selected LiPF Hydrolysis Products on the High Voltage Stability of Lithium-Ion Battery Cells.

ACS Appl Mater Interfaces 2016 Nov 4;8(45):30871-30878. Epub 2016 Nov 4.

MEET Battery Research Center/Institute of Physical Chemistry, University of Münster , Corrensstrasse 46, 48149 Münster, Germany.

Diverse LiPF hydrolysis products evolve during lithium-ion battery cell operation at elevated operation temperatures and high operation voltages. However, their impact on the formation and stability of the electrode/electrolyte interfaces is not yet investigated and understood. In this work, literature-known hydrolysis products of LiPF dimethyl fluorophosphate (DMFP) and diethyl fluorophosphate (DEFP) were synthesized and characterized. The use of DMFP and DEFP as electrolyte additive in 1 M LiPF in EC:EMC (1:1, by wt) was investigated in LiNiMnCoO/Li half cells. When charged to a cutoff potential of 4.6 V vs Li/Li, the additive containing cells showed improved cycling stability, increased Coulombic efficiencies, and prolonged shelf life. Furthermore, low amounts (1 wt % in this study) of the aforementioned additives did not show any negative effect on the cycling stability of graphite/Li half cells. DMFP and DEFP are susceptible to oxidation and contribute to the formation of an effective cathode/electrolyte interphase as confirmed by means of electrochemical stability window determination, and X-ray photoelectron spectroscopy characterization of pristine and cycled electrodes, and they are supported by computational calculations.
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November 2016