In-operando GC-MS: A new tool for the understanding of degradation processes occurring in electrochemical capacitors
Fabian Alexander Kreth, Lars H. Heß, Andrea Balducci
Abstract
In this work, we present an innovative design of an electrochemical three-electrode cell for in-operando gas chromatography-mass spectrometry analysis, which allows performing electrochemical measurements while probing and analyzing the liquid electrolyte in real-time. The presented cell shows similar electrochemical performance to commonly used lab-scale cells and can be utilized for the investigation of any kind of electrochemical system. The three-electrode configuration enables the differentiation of processes occurring at the respective positive or negative electrode. Investigating the aging of electrochemical cells, it is possible to obtain a detailed time-resolved insight into occurring decomposition processes. As a model case, we investigated aging processes occurring in an electric double-layer capacitor containing a one-molar solution of tetraethylammonium tetrafluoroborate in acetonitrile. Showing a time- and voltage-dependent evolution, decomposition products of the salt, solvent, and electrode were detected and assigned to aging processes occurring at the respective positive and/or negative electrode-electrolyte interphase. Used for the detection of soluble decomposition species within the electrolyte, in-operando gas chromatography-mass spectrometry is uniquely suited to be combined with techniques focused on the electrode and/or gas phase of electrochemical energy storage devices.