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Electrochemical measurement techniques

Electrochemical measurement techniques

As the core component of the overall solid oxide cell (SOC) system, the performance and stability of the SOC stacks are of the most importance. With common DC techniques, it’s possible to record the performance variation of the total stack or each repeating unit inside. However, determinations of the reaction and degradation mechanisms are nearly impossible, before any post-mortem analysis. With AC technique, in-situ separation of the different contribution to the total resistance of each repeating unit and stack becomes possible. One focus of the research is the electrochemical characterization and analysis of SOC stacks, inter alia by means of electrochemical impedance spectroscopy (EIS). With the help of DRT technique (Distribution of Relaxation Times), the relatively poorer resolution of Nyquist plot, Bode plot and equivalent circuit model, regarding EIS analysis, can be overcome to a great extent.

Besides the electrochemical performance of the stacks, the thermo-mechanical stability and threshold are studied to further improve the stack design, and to optimize the operating parameters/strategies of SOC stacks/systems. Stack diagnoses, including detection of any mechanical failures during operation by combination of physical sensing techniques and electrochemical analysis, is the main task here. All findings are used to further improve the stack design and for validation in the development of computational models.

Based on the long-standing experience on stack endurance and cycling tests, as well as the established comprehensive know-how on degradation mechanisms of stacks, a methodology of accelerated stress test (AST) will be developed.