Impedance-based Solid Oxide Fuel Cell testing as scalable and reliable Quality Control tool for cell and batch manufacturing: first findings

Abstract

Testing is a necessary step in the manufacturing process of Solid Oxide Fuel Cells (SOFC) to assess the performance of the produced cells before on-field deployment. In this work, the implementation of Electrochemical Impedance Spectroscopy (EIS) and subsequent data elaboration via Equivalent Circuit Modelling (ECM) is evaluated as a viable experimental framework for characterization and Quality Control (QC) of cells or cell batches, complemented to standard polarization-based methods. By performing a statistical analysis of the ECM parameters (representative of each physico-chemical process) the cell and batch operational parameters can be determined and compared. The validity of the proposed methodology is assessed using a wide experimental dataset of a significant number of SOFC samples (20 cells from 3 batches – two of which identical and the third with an intentional modification in the manufacturing process in order to validate the proposed methodology) tested in identical conditions. Results show that the impedance-based method provide detailed information in terms of impedance breakdown (anode gas diffusion process resulting the main criticality), as well as confirming the preliminary results obtained from the polarization approach (Batch#2 showing the lowest total performance and highest uniformity). Highly reproducible intra-batch distributions of the ECM parameters encourage the applicability of such methodology for QC purposes, even with few data collected only in Open Circuit Voltage (OCV) conditions. A relevant deviation of charge transfer and diffusion resistances in Batch#3 respect to other batches is observed (not visible from the polarization curves), which is reconducted to the modified anode functional layer, opening potential applications of the proposed methodology to assess the impact of targeted modifications of manufacturing methods on specific cell electrochemical performances.

Performance Evaluation of an Anode-Supported SOFC Short-Stack Operating with Different Fuel Blends as Stationary-CHP System

“…For the 100% H 2 composition, some formulations of the efficiency (Eqs. [21][22][23][24][25][26][27][28][29][30][31][32] are not defined because the contribution given by the carbon-containing gases is non-existent, hence they lead to identical results.…”

“…The SOFC stack is based on State of the Art materials and thanks to its Anode Supported Cell (ASC) configuration with very thin electrode, it can be operated at a nominal temperature as low as 600 °C-700 °C (so called Intermediate Temperature SOFC, or IT-SOFC). 28 The stack is based on a closed air/fuel architecture, in which a manifold structure provides fuel/air to each unit layer and is accessible for temperature/pressure measurements. The insulation between adjacent cell layers is guaranteed by pre-mounted glassbased sealings.…”

Performance Evaluation of an Anode-Supported Solid Oxide Fuel Cell Short-Stack Operating with Different Hydrogen-Natural Gas Blends as Stationary Combined Heat and Power System

“…The short stack E350 is tested in order to characterize the electrochemical performances (polarization curves and short-term stability tests) as well as map its performances in stationary conditions (output power and stack-level efficiency) at smaller scale. The SOFC stack is based on State of the Art materials and thanks to its Anode Supported Cell (ASC) configuration with very thin electrode can be operated at a nominal operating temperature as low as 600-700°C (so called Intermediate Temperature SOFC IT-SOFC) [17].…”

Developing an Automated Tool for Quantitative Analysis of the Deconvoluted Electrochemical Impedance Response of a Solid Oxide Fuel Cell

“…For electrochemical impedance spectroscopy measurements, the setup was equipped with a Solartron 1260 frequency response analyzer module and a coupled Solartron 1287 Electrochemical Interface. More details regarding the test rig can be found in [25]. Three different production batches (Batch 1, 7 cells; Batch 2, 11 cells; Batch 3, 5 cells; for a total of 23 cells) of the same cell design were tested.…”

“…Furthermore, the DRT enables the accurate distinction of each polarization process's characteristic frequencies and qualitative analysis of the extent of its effect on the overall polarization spectra [23], see Figure 1. By comparing DRT spectra obtained with the same experimental procedures of the SOFC sample under different experimental conditions (e.g., variation of temperatures or reactant compositions), it is possible to ascertain the latter's influence on SOFC processes by analyzing the shifts in the DRT peaks and their characteristic frequency bandwidths [24,25]. However, DRT shifts are often analyzed only qualitatively by visual inspection since a quantitative analysis is cumbersome [26,27].…”