SOC Stack Impedance Characterization and Identification Based on DRT and ADIS Methods

Electrochemical analysis and diagnosis of the SOC stacks, including Solid Oxide Fuel Cells (SOFC) and Solid Oxide Electrolysis Cells (SOEC), are one of the research challenges in world. In order to optimize performance and realize practical SOC application, it is crucial to investigate kinetic mechanisms and reaction principle of the multiple-cells stack. In this paper, the relaxation time distribution method (DRT) combined with the analysis of difference in impedance spectra method (ADIS) were employed to research the complex electrochemical behavior of SOC stacks under different operation modes. The DRT characteristic peaks were identified through the analysis and as-segment of the relaxation time. The changes in the DRT peaks were correlated with the different electrochemical process. The research achievements indicate that the water content should be more than 20% when operated at SOFC mode, while less than 80% when operated at SOEC mode to minimize the gas diffusion resistance. The research achievements can provide theoretical data and establish technical foundation for the further study and application of this novel method, which can reduce the SOC complexity of EIS analysis, apply for the degradation identification and online diagnosis of stacks, and help to improve the SOC performance.