SOFC Cathode Materials

Overview

La_0.8Sr_0.2Ga_0.8Mg_0.115Co_0.085O_3-δ (LSGMC) has been reported as an optimized composition of LSGM-based electrolytes

• High conductivity at intermediate temperatures, i.e., 500-700^oC.

The SOFC cathode, where molecular oxygen is adsorbed, converted to ions and introduced to the ion conductor, is critical to performance

The air cathode is typically bi-functional with both electronic and ionic conducting characteristics.

Several state-of-the-art materials are considered for our intermediate temperature IT-SOFCs:

• Sm_1-xSr_xCoO_3-δ (SSC)
• Ba_1-xLa_xCoO_3-δ (BLC)
• La_1-xSr_xCo_1-yFe_yO_3-ζ (LSCF)

Goals and Objectives

By precisely controlling nitrate stoichiometry, synthesize perovskite-type oxides via
glycine-nitrate combustion method

• favorable for the reduction of impurity phases
• good electrical properties were obtained from the samples.

Use AC impedance spectrometry to show that LSGMC has lower impedance compared with conventional baseline electrolyte material 8-YSZ

• Optimization of composition and cell manufacturing processes can result in much higher ionic conductivity and SOFC power density

Show that composite cathodes perform better than the pure cathodes with significantly reduced polarization resistances

Perform additional electrochemical analyses, microstructural characterizations, and measurements of interfacial properties on cathodes/LSGMC systems to determine whether this materials set could be promising as an IT-SOFC

Experimental Apparatus for DC Polarization Test

XRD pattern of SSC powder calcined at 900°C

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XRD pattern of LSCF powder calcined at 900°C

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XRD pattern comparison of LSGMC

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Stoichiometry Control for LSGMC

Gallium precursor contents play a key role in desired LSGMC stoichiometry

Lattice water value x in Ga (NO3)3▪ x H2O determined:

• CIS result from manufacturer: 8.88
  
• TGA measurement: 4.58
  
• AA test: 8.90

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XRD pattern comparison of LSGMC

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SEM Micrographs of Cathodes

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Conductivity Measurement for LSGMCDC Polarization: pure SSC on LSGMC

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Conductivity of LSGMC

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DC polarization performance comparison

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Personnel

Investigators:  X. Lu, J. Brouwer, D. Mumm, and G.S. Samuelsen
Staff:  R.L. Hack, M.D. Crespin
Students:  Grace Ya Qin

Sponsors

U.S. Department of Defense, Fuel Cell Program
Edison Materials Technology Center

 

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