Evaluation and Modelling of the Cell Resistance in Anode Supported Solid Oxide Fuel Cells

Leonide, André; Sonn, Volker; Weber, André; Ivers‐Tiffée, Ellen

doi:10.1149/1.2729132

Cited by 34 publications

(26 citation statements)

References 7 publications

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“…-Growth of the oxide scale on the surface of metallic interconnects at stack operating temperatures, even under the protective coating, increases the ohmic resistance. -Compared to the DRT analysis of single cells, [25][26][27][28] no additional processes were observed in the stack under current testing conditions and analytical procedures. The metallic interconnect and the protective coating, as well as the contact materials at both electrodes had only an influence on the ohmic resistance.…”

Section: Resultsmentioning

confidence: 97%

“…However, comprehensive EIS measurements and DRT analysis using J ÜLICH's ASC single cells and/or symmetrical cells have been carried out at the Institute for Applied Materials -Materials for Electrical and Electronic Engineering (IAM-WET) at the Karlsruhe Institute of Technology (KIT). 15,[25][26][27][28] Based on the results from single cell measurements, as well as previous DRT studies with F-design short stacks (0.1-10 kHz), the three processes obtained in DRT shown in Figure 12 can be identified and are listed in Table II. Another process, which is not listed in Table II, could also be observed in the stacks between 0.1 Hz and 1 Hz, when oxygen partial pressure is below 5%.…”

Section: Resultsmentioning

confidence: 99%

“…Based on a comprehensive characterization and investigation of SOFC single cells (ASCs from J ÜLICH) by means of a DRT analysis, 15,[25][26][27][28] the SOFC/SOEC stacks using the same types of cell were analyzed with EIS, following a similar route. In this work, the performance and degradation behavior of a two-layer F10-design SOEC stack at 700 • C and 800 • C will be discussed with the support of EIS and DRT.…”

mentioning

confidence: 99%

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Performance and Degradation of Solid Oxide Electrolysis Cells in Stack

Fang

Blum

Menzler

2015

J. Electrochem. Soc.

103

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A Solid Oxide Electrolysis (SOE) short stack consisting of anode-supported cells (ASCs in fuel cell mode) was assembled in J ÜLICH's F10-design. ASCs are based on Ni/8YSZ (8 mol-% yttria-stabilized zirconia) with an LSCF air electrode (La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ ) and 8YSZ electrolyte. A gadolinium-doped ceria (GDC) (Ce 0.8 Gd 0.2 O 1.9 ) barrier layer was deposited between 8YSZ and LSCF by means of physical vapor deposition (PVD). The stack was mainly characterized in a furnace environment in both fuel cell and electrolysis modes, with 50% humidified H 2 at 700 and 800 • C. An endothermic long-term electrolysis operation was carried out at 800 • C with a current density of −0.5 Acm −2 and steam conversion rate of 50%. After 2300 h of operation, the stack showed an average voltage degradation rate of 0.7%/kh. Electrochemical impedance spectroscopy (EIS) and analysis of the distribution function of relaxation times (DRT) showed that the degradation was primarily due to the increase in ohmic resistance.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Performance and Degradation of Solid Oxide Electrolysis Cells in Stack

Fang

Blum

Menzler

2015

J. Electrochem. Soc.

103

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“…All parameters were chosen on the basis of previous experiments. The distribution function of relaxation times (DRT) [13][14][15] was calculated from the real part of the measured impedance data by employing the FTIKREG 16 software package from the CPC Program Library.…”

Section: Methodsmentioning

confidence: 99%

Electrochemical Performance and Preliminary Post-Mortem Analysis of a Solid Oxide Cell Stack with 20,000 h of Operation

Fang

Frey

Menzler

et al. 2018

J. Electrochem. Soc.

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A long-term test with a two-layer solid oxide cell stack was carried out for more than 20,000 hours. The stack was mainly characterized in a furnace environment in electrolysis mode, with 50% humidification of H 2 at 800 • C. The endothermic operation was carried out with a current density of −0.5 Acm −2 and steam conversion rate of 50%. Electrolysis at lower temperatures (i.e., 700 • C and 750 • C) and fuel cell operation (with 0.5 Acm −2 and fuel utilization of 50%) at 800 • C were also carried out (<2000 h each) for comparison. The voltage and area specific resistance degradation rates were ∼0.6%/kh and 8.2%/kh after ∼18,460 hours of operation. In total, the stack was operated above 700 • C for more than 20,000 hours. Impedance measurement and analysis showed that the increase of ohmic resistance was the main degradation phenomenon, while electrode polarizations were kept nearly constant before a severe burning took place in one layer. Ni-depletion in fuel electrodes was confirmed during post-mortem analysis, which was assumed to be the major degradation mechanism observed. The stack performance and degradation analysis under different working conditions, as well as the results of preliminary post-mortem analysis will be presented. One of the critical challenges to the application and commercialization of solid oxide cell (SOC) technology is the long-term stability of complete systems, stacks and single components. Despite the fact that accelerating methods have long been under discussion, the time-consuming and costly endurance tests of stacks and cells under relevant conditions are still necessary for reliable degradation analyses and lifetime prediction. Compared to the tests with single cell or other stack and system component, the results of long-term degradation tests with stacks are quite limited. [1][2][3][4][5] Previous results have shown stable performance of stacks working in the temperature range of 700-800• C in SOFC mode. [6][7][8][9] Recently, a short stack achieved a 10 years lifetime, and remains in operation. 10 With proper protective coating, a voltage degradation rate of less than 0.3%/kh and lifetime of more than 40,000 h at 700• C is possible with current stack design and components. In contrast to the low degradation rate in SOFC mode, higher degradation rates of ∼0.6-1.5%/kh were observed with similar types of cells in the same stack design in SOEC mode, as described by Nguyen et al. 11 Therefore, the functionality and optimization potential of the cells and stacks, as well as their long-term degradation behavior and mechanisms in SOEC mode, needs to be further investigated. Amongst the stacks operated in SOEC mode, a two-layer stack was operated under different stationary conditions for more than 20,000 h. The stack performance was regularly monitored by open circuit voltage, voltage-current curves and impedance measurements. After cooling down, one third of the stack was embedded in resin for cross-section preparation, and the rest was disassembled for visual inspection. The prelim...

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“…74) Since then, the analysis of degradation phenomena by means of the DRT was applied in a number of studies. In 75),76) chromium poisoning effects were analyzed, while 77) reveals details about sulfur poisoning of Ni/YSZ cermet anodes, 78) provides information about the excellent redox stability of strontium titanate based ASCs and 79) discusses the performance and stability of SOFCs operated in a biogas fuel. The DRT analysis revealed an impact on the hydrogen electrooxidation in the AFL (P 2A ,P 3A ) and an increase in the gas diffusion polarization (P 1A ), both attributed to carbon deposition in the AFL and the substrate.…”

Section: Drt-analysis Of Degradation Phenomenamentioning

confidence: 99%

Evaluation of electrochemical impedance spectra by the distribution of relaxation times

Ivers‐Tiffée

Weber

2017

J. Ceram. Soc. Japan

252

109

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Electrochemical impedance spectroscopy is a well suited method for studying the properties of electrochemical systems. In recent decades electrochemical systems were investigated at different scales, from small model electrodes to high power devices, such as fuel cells and batteries. In the latter case, the measurement of reliable spectra and their evaluation is challenging because (i) the impedance is usually very low (1 ³), (ii) there is more than one rate limiting, electrochemical process per electrode, (iii) their charge transfer and transport processes are coupled and (iv) cathodic and anodic contributions overlap in the frequency domain. The Distribution of Relaxation Times (DRT) is supportive when deconvoluting complex impedance spectra, and has therefore gained increased attention. In this paper we introduce selected results of advanced impedance analysis. We discuss the impact of impedance data quality, statistically distributed noise and single errors in the spectra. Furthermore, the applicability of DRT for establishing adequate equivalent circuit models for ceramic electrochemical devices, such as batteries and fuel cells will be discussed.

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Evaluation and Modelling of the Cell Resistance in Anode Supported Solid Oxide Fuel Cells

Cited by 34 publications

References 7 publications

Performance and Degradation of Solid Oxide Electrolysis Cells in Stack

Performance and Degradation of Solid Oxide Electrolysis Cells in Stack

Electrochemical Performance and Preliminary Post-Mortem Analysis of a Solid Oxide Cell Stack with 20,000 h of Operation

Evaluation of electrochemical impedance spectra by the distribution of relaxation times

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