Break Down of Losses in Thin Electrolyte SOFCs

Barfod, Rasmus; Hagen, Anke; Ramousse, Séverine; Hendriksen, Peter Vang; Mogensen, Mogens Bjerg

doi:10.1002/fuce.200500113

Cited by 110 publications

(106 citation statements)

References 20 publications

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“…The LF and MF responses grow larger and shift to lower frequency with decreasing pH 2 , but the HF response increases only very slightly. These frequencies agree well with those normally observed for Ni-YSZ anodes, 21,22 and are correlated to anode gas conversion (∼1 Hz), anode gas diffusion (∼10 Hz) and charge transfer …”

Section: Electrochemical Characterization-fig 5 Compares the Voltagsupporting

confidence: 89%

Anode-Supported Solid Oxide Fuel Cells Fabricated by Single Step Reduced-Temperature Co-Firing

Wang

Gao

Barnett

2015

J. Electrochem. Soc.

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Anode-supported solid oxide fuel cells (SOFCs) consisting of NiO-Y 0.16 Zr 0.92 O 2-δ (YSZ) anode support layer, NiO-YSZ anode functional layer, YSZ electrolyte and (La 0.8 Sr 0.2 ) 0.98 MnO 3-δ (LSM)-YSZ cathode were successfully fabricated by single-step cofiring at 1250 • C. Cells were prepared by tape casting, with Fe 2 O 3 sintering aid used to obtain a nearly dense YSZ electrolyte. Scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDS) showed no evidence of reactions or interdiffusion between layers during co-firing. The cells yielded area specific resistance of 0.44 cm 2 and a maximum power density of 0.91 W/cm 2 at 800 • C. Impedance spectroscopy measurements showed that the LSM-YSZ cathode polarization resistance was higher for the co-fired cathodes than for a cathode that was fired separately at an optimized temperature of 1175 • C. However, reducing the cell co-firing time decreased cathode polarization resistance and increased cell power output. Analysis of SEM images showed that co-firing caused more sintering and coarsening than in the optimally-fired LSM-YSZ, reducing three-phase boundary density and explaining the increased cathode resistance. Anode-supported solid oxide fuel cells (SOFCs) with yttriastabilized zirconia (YSZ) electrolytes are usually fabricated using at least two high-temperature firing steps: co-firing of the anode and electrolyte followed by application and firing of the cathode.1,2 This is based primarily on differences in desired firing temperatures -the YSZ electrolyte is densified at ∼ 1400• C -whereas cathode materials, typically based on (La 0.8 Sr 0.2 ) 0.98 MnO 3-δ (LSM), are usually fired at 1200 • C. Also, the two-step process reduces possible reactions between cathode and electrolyte during firing. On the other hand, there are a number of reasons why single-step fired SOFCs are desirable. First, it simplifies the process, reducing the processing time and input energy, important given the general need to reduce SOFC cost in order to improve commercial viability.3-7 Second, single-step co-firing is a requirement for fabrication strategies where the entire stack, including cells, gas channels and interconnectors, are fired together.8 Third, it allows the fabrication of cells with a cathode-side mechanical support instead of an anode support.In order to achieve single-step firing, the temperature should be reduced to allow a good cathode microstructure, while still densifying the YSZ electrolyte. YSZ electrolyte densification as low as 1200• C has been demonstrated when utilizing an appropriate sintering aid, e.g. Fe 2 O 3 .9,10 Recently, anode-supported SOFCs with YSZ/GDC bi-layer electrolytes have been produced by co-firing with Fe 2 O 3 sintering aid at 1250• C, but with the cathode added in a second lower-temperature firing step.11 These temperatures are still above the ideal firing temperature for LSM-YSZ cathodes of ∼ 1175• C. 12 Also, the shrinkage that occurs during single-step co-firing will exacerbate cathode densification, further reduci...

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Section: Electrochemical Characterization-fig 5 Compares the Voltagsupporting

confidence: 89%

Anode-Supported Solid Oxide Fuel Cells Fabricated by Single Step Reduced-Temperature Co-Firing

Wang

Gao

Barnett

2015

J. Electrochem. Soc.

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“…The precise deposition achievable with an inkjet printing approach reported here avoids those inherent materials wastage and accumulation problems. However, our results broadly agree; anode infiltration alone did not significantly enhance the electrochemical performance of commercial cells at intermediate temperatures, due to the dominance of cathode losses [26]. The benefit of anode infiltration in commercial cells may be more pronounced for long term stability and fuel impurity tolerance [8,27,28].…”

Section: Full Cell Electrochemical Performancesupporting

confidence: 69%

Infiltration of commercially available, anode supported SOFC’s via inkjet printing

Mitchell-Williams

Tomov

Saadabadi

et al. 2017

Mater Renew Sustain Energy

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Commercially available anode supported solid oxide fuel cells (NiO-8YSZ/8YSZ/LSCF-20 mm in diameter) were anode infiltrated with gadolinium doped ceria (CGO) using a scalable drop-on-demand inkjet printing process. Cells were infiltrated with two different precursor solutions-water based or propionic acid based. The saturation limit of the 0.5 lm thick anode supports sintered at 1400°C was found to be approximately 1wt%. No significant enhancement in power output was recorded at practical voltage levels. Microstructural characterisation was carried out after electrochemical performance testing using high resolution scanning electron microscopy. This work demonstrates that despite the feasibility of achieving CGO nanoparticle infiltration into thick, commercial SOFC anodes with a simple, low-cost and industrially scalable procedure other loss mechanisms were dominant. Infiltration of model symmetric anode cells with the propionic acid based ink demonstrated that significant reductions in polarisation resistance were possible.

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“…[5][6][7][8][9] Looking at the SOFC system perspective it is insufficient only to improve a single cell component in order to drastically increase the cell performance as it has been shown that all cell components (cathode, electrolyte, and anode) contribute with considerable losses in the SOFC. [10] Therefore, work on novel cathode materials is highly important. Fe-Co perovskites, such as (La,Sr)(Co,Fe)O 3−δ (LSCF), are an alternative class of cathode materials, instead of the traditional YSZ/LSM cathode, as they have lower polarization resistance.…”

Section: Introductionmentioning

confidence: 99%

Strontium Diffusion in Magnetron Sputtered Gadolinia‐Doped Ceria Thin Film Barrier Coatings for Solid Oxide Fuel Cells

Sønderby

Popa

et al. 2013

Advanced Energy Materials

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is prepared to simulate a solid oxide fuel cell. This setup allows observation of Sr diffusion by observing SrZrO 3 formation using X-ray diffraction while annealing. Subsequent electron microscopy confirms the results. This approach presents a simple method for assessing the quality of CGO barriers without the need for a complete fuel cell test setup. CGO films with thicknesses ranging from 250 nm to 1.2 µm are tested at temperatures from 850 °C to 950 °C which yields an in-depth understanding of Sr diffusion through CGO thin films that may be of high scientific and technical interest for implementation of novel fuel cell materials. Sr is found to diffuse along column/grain boundaries in the CGO films but by modifying the film thickness and microstructure the breaking temperature of the barrier can be increased.2 2

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Break Down of Losses in Thin Electrolyte SOFCs

Cited by 110 publications

References 20 publications

Anode-Supported Solid Oxide Fuel Cells Fabricated by Single Step Reduced-Temperature Co-Firing

Anode-Supported Solid Oxide Fuel Cells Fabricated by Single Step Reduced-Temperature Co-Firing

Infiltration of commercially available, anode supported SOFC’s via inkjet printing

Strontium Diffusion in Magnetron Sputtered Gadolinia‐Doped Ceria Thin Film Barrier Coatings for Solid Oxide Fuel Cells

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