Nano-structured composite cathodes for intermediate-temperature solid oxide fuel cells via an infiltration/impregnation technique

Jiang, Zaihong; Xia, Changrong; Chen, Fanglin

doi:10.1016/j.electacta.2010.02.019

Cited by 258 publications

(174 citation statements)

References 126 publications

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“…Eventually, this matches the concept of scaffold electrodes, [65][66][67][68][69][70] that is, electrodes fabricated with a porous ionic backbone which is infiltrated with electronconducting particles or even a mixture of electron-conducting and ionconducting particles. In other words, the optimal 3D printed electrode with rectangular pillars results in the production of a scaffold with well-defined geometry; r the upper bound in performance can be analytically predicted through the approximated model reported in Eqs.…”

Section: Resultsmentioning

confidence: 99%

Guidelines for the Rational Design and Engineering of 3D Manufactured Solid Oxide Fuel Cell Composite Electrodes

Bertei

Tariq

Yufit

et al. 2016

J. Electrochem. Soc.

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The growth of 3D printing has opened the scope for designing microstructures for solid oxide fuel cells (SOFCs) with improved power density and lifetime. This technique can introduce structural modifications at a scale larger than particle size but smaller than cell size, such as by inserting electrolyte pillars of ∼5-100 μm. This study sets the minimum requirements for the rational design of 3D printed electrodes based on an electrochemical model and analytical solutions for functional layers with negligible electronic resistance and no mixed conduction. Results show that this structural modification enhances the power density when the ratio k eff between effective conductivity and bulk conductivity of the ionic phase is smaller than 0.5. The maximum performance improvement is predicted as a function of k eff . A design study on a wide range of pillar shapes indicates that improvements are achieved by any structural modification which provides ionic conduction up to a characteristic thickness ∼10-40 μm without removing active volume at the electrolyte interface. The best performance is reached for thin (<∼2 μm) and long (>∼80 μm) pillars when the composite electrode is optimised for maximum three-phase boundary density, pointing toward the design of scaffolds with well-defined geometry and fractal structures. Many studies in the literature have recognised the importance of the electrode microstructure in affecting the power density and the lifetime of solid oxide fuel cells (SOFCs).1-7 Significant enhancements in power density have been achieved through the statistical control of the microstructural properties by tuning porosity, 8,9 volume fractions, 2,8,10 particle size 11-13 and even tortuosity of the phases.14 However, nowadays the design of the electrode microstructure can be optimised with unprecedented precision through the advent of 3D printing and additive manufacturing techniques. 15-17Additive manufacturing allows for the development of electrodes with 3D architectures, thus going beyond what conventional fabrication techniques, such as tape casting and screen printing, can produce. The exploitation of 3D additive manufacturing has been successfully applied by the battery community [18][19][20] and the implementation of this approach to SOFCs is currently under investigation.15,21 One of the most promising applications consists of the insertion of ionconducting pillars connected to the electrolyte 15,[22][23][24][25] as reported in Figure 1. Such a modification can be regarded as the mesoscale structural control of electrode microstructure, where the term mesoscale here refers to a dimension larger than the typical constituent particle size (<1 μm) but smaller than the characteristic length of the cell, that is, falling in the order of 5-100 μm.26 Ideally, 3D printing offers the opportunity to controllably manufacture pillars of any shape, with the desired geometric and spacing requirements, in order to provide a preferential pathway for ionic conduction. 22,25 It is important to note that this mesos...

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Section: Resultsmentioning

confidence: 99%

Guidelines for the Rational Design and Engineering of 3D Manufactured Solid Oxide Fuel Cell Composite Electrodes

Bertei

Tariq

Yufit

et al. 2016

J. Electrochem. Soc.

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“…2,11,23 The work we present here makes a strong case that we should also be thinking about how to decrease the characteristic particle size, and increase the initial surface area, of the scaffold. Our results show that the active TPB density can be increased by an order of magnitude with this approach.…”

Section: Discussionmentioning

confidence: 99%

“…The first morphological advantage is a mitigation of the coefficient of thermal expansion (CTE) mismatch between the electrolyte and the electrode. 10,11 The second advantage is a stabilization of the electrode mechanical properties during redox cycling, 5,12 Finally, less material is needed to form an interconnected network of the infiltrated phase throughout the electrode. 6,10,[12][13][14][15] Although the benefits of infiltrated electrodes have been clearly demonstrated experimentally, researchers suggest that the electrode designs are not optimized.…”

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confidence: 99%

Insights into the Design of SOFC Infiltrated Electrodes with Optimized Active TPB Density via Mechanistic Modeling

Reszka

Snyder

Gross

2014

J. Electrochem. Soc.

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A mechanistic model for the prediction of total and active three phase boundary density (TPB), in combination with effective conductivity, of infiltrated solid oxide fuel cell (SOFC) electrodes is presented. Varied porosities, scaffold:infiltrate size ratios, and pore:infiltrate size ratios were considered, each as a function of infiltrate loading. The results are presented in dimensionless form to allow for the calculation of any infiltrate particle size. The model output compares favorably to the available experimental result. The results show that the scaffold:infiltrate size ratio has the greatest impact on the TPB density, followed by the porosity and then the pore:infiltrate size ratio. The TPB density is shown to monotonically decrease with increasing scaffold:infiltrate and pore:infiltrate size ratios; however, it shows a maximum with respect to porosity. Each of these results are explained by examining the interfacial areas of each of the three phases as a function of the infiltrate loading. The model provides insight toward the rational design of infiltrated electrodes. Infiltrated solid oxide fuel cell (SOFC) electrodes offer numerous advantages over conventional co-sintered electrodes. First, a broader choice of electrode materials is possible because materials that melt or chemically react with the electrolyte at conventional sintering temperatures can be considered.1-6 Second, a higher three-phase boundary (TPB) density can be achieved, which is attributed to the smaller particle sizes.2,3,7-9 These two advantages result from a lower processing temperature of the infiltrated phase compared to conventional sintering temperatures required of co-sintered electrodes.Three additional advantages of infiltrated electrodes are associated with the unique morphology created by coating the surface of a presintered porous scaffolding with an infiltrated phase. The first morphological advantage is a mitigation of the coefficient of thermal expansion (CTE) mismatch between the electrolyte and the electrode. 10,11The second advantage is a stabilization of the electrode mechanical properties during redox cycling, 5,12 Finally, less material is needed to form an interconnected network of the infiltrated phase throughout the electrode. 6,10,[12][13][14][15] Although the benefits of infiltrated electrodes have been clearly demonstrated experimentally, researchers suggest that the electrode designs are not optimized. 3,5,6,14,16 This is understandable because it is laborious to consider all of the combinations and permutations of the sizes and shapes of infiltrate particles, scaffold particles, and pores as well as the wide range of possible porosities. In order to more effectively and efficiently design electrodes, several computational models have been recently reported. Zhang et al. utilized a particle-layer model to estimate the TPB density, effective thickness of the electrochemically active region, and polarization resistance of cathodes.9 A more recent report by Zhang et al. utilized a numerically generated thr...

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“…Lab scale infiltration of both cathode and anodes has been demonstrated by various groups [9,10] in laboratory conditions. The infiltration is usually performed with micro pipette drop delivery or sample immersion.…”

Section: Introductionmentioning

confidence: 99%

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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Nano-structured composite cathodes for intermediate-temperature solid oxide fuel cells via an infiltration/impregnation technique

Cited by 258 publications

References 126 publications

Guidelines for the Rational Design and Engineering of 3D Manufactured Solid Oxide Fuel Cell Composite Electrodes

Guidelines for the Rational Design and Engineering of 3D Manufactured Solid Oxide Fuel Cell Composite Electrodes

Insights into the Design of SOFC Infiltrated Electrodes with Optimized Active TPB Density via Mechanistic Modeling

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

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