Elsevier

Journal of Power Sources

Volume 185, Issue 2, 1 December 2008, Pages 784-789
Journal of Power Sources

Interaction of La0.8Sr0.2MnO3 interlayer with Gd0.1Ce0.9O1.95 electrolyte membrane and Ba0.5Sr0.5Co0.8Fe0.2O3−δ cathode in low-temperature solid oxide fuel cells

https://doi.org/10.1016/j.jpowsour.2008.07.054Get rights and content

Abstract

Low-temperature solid oxide fuel cells with a La0.8Sr0.2MnO3 (LSM) interlayer between the Ce0.9Gd0.1O1.95 (GDC) electrolyte membrane (20 μm) and the Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF)–GDC composite cathode are fabricated by sintering the BSCF–GDC composite cathodes at 900, 950 and 1000 °C. The results of scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) for a model LSM/BSCF bi-layer pellet suggest that Ba, Co and Fe in BSCF as well as La and Mn in LSM have diffused into their counter sides. The X-ray diffraction (XRD) results on the simulated cells also indicate the incorporation of La into the GDC electrolyte membrane and the mutual diffusion of elements between the LSM layer and the BSCF layer. Analysis of the impedance spectra and interfacial reaction activation energies shows that LSM interlayer accelerates the oxygen reduction. Considering a good cell performance and the highest open-circuit voltages (OCVs) at 600–500 °C, the optimum sintering temperature of BSCF–GDC composite cathode onto LSM interlayer is 900 °C.

Introduction

The high temperature fabrication and operation of solid oxide fuel cells (SOFCs) lead to elemental diffusions and reactions between different phases and layers, which have a great impact on the cell performances. Our previous researches on the anode-supported La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM)–La0.45Ce0.55O2 (LDC) bi-layered electrolyte cell depicted that this cell had lower open-circuit voltage (OCV) and lower specific ohmic resistance than expected, which can be assigned to the diffusion of Co from La0.6Sr0.4CoO3 (LSC) cathode to LSGM electrolyte [1], [2], [3]. A work on an all-perovskite fuel cell done by Tao et al. [4] suggested that a slight cross-diffusion at the interfaces between different perovskite components might improve the interfacial contact and decrease the interfacial resistance. La cations could diffuse into yttria-stabilized zirconia (YSZ) electrolyte from Sr-doped lanthanum manganite (LSM) cathode, which lowered the cathode performance [5], [6]. Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF)–LaCoO3 (LC) composite cathode had the higher electronic conductivity than the single BSCF cathode because of the solid-state reaction between BSCF and LC [7].

Recently, we fabricated a low-temperature solid oxide fuel cell with a La0.8Sr0.2MnO3 (LSM) interlayer between Ce0.9Gd0.1O1.95 (GDC) electrolyte membrane and Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF)–GDC composite cathode, and this cell showed the improved cell performance than the unmodified one [8]. In this cell, the elemental diffusion from BSCF cathode to LSM interlayer seems to play an important role. Of course, at a specific sintering temperature of LSM interlayer, the interaction between LSM and BSCF depends on the sintering temperature of the BSCF–GDC composite cathode. In this paper, the interaction between LSM interlayer and GDC electrolyte as well as BSCF cathode is investigated, and its effects on cell performance are elucidated.

Section snippets

Materials synthesis and cell fabrication

The home-made BSCF, LSM and GDC powders were synthesized by the sol–gel process. Anode-supported thin electrolyte (20 μm) bi-layer assemblies were fabricated using a dual dry-pressing method. The anode, consisted of a 50:50 wt.% mixture of NiO and GDC powders was dry-pressed into a pellet, and then an appropriate amount of the GDC electrolyte powder was distributed on the anode surface and co-pressed with the anode using a uniaxial die-press (Ø25 mm). The resultant bi-layer was sintered at 1420 °C

SEM/EDX analysis of a model LSM/BSCF bi-layer pellet

Information on the possible elemental inter-diffusion between LSM interlayer and BSCF cathode layer can be provided by examining a model LSM/BSCF bi-layer pellet through microanalysis. Fig. 1a shows the microstructure of the model LSM/BSCF pellet. It can be observed that the pellet is not densely sintered after the thermal treatment. For this reason, the elemental profiles presented in Fig. 1b can only be used for semi-quantitative statements. As shown in Fig. 1b, a distinct congregation of all

Conclusions

Low-temperature SOFCs with LSM interlayer between GDC electrolyte membrane and Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF)–GDC cathode were fabricated at the cathode sintering temperature of 900, 950 and 1000 °C. The EDX line scan analysis of a model LSM/BSCF double layer identified the transport of Co, Ba and Fe from BSCF into LSM, and simultaneous migration of Mn and La from LSM to BSCF. XRD results also suggested the inter-diffusion between LSM interlayer and GDC electrolyte as well as BSCF cathode. LSM

Acknowledgements

The authors gratefully acknowledge financial supports from the Ministry of Science and Technology of China (nos. 2004CB719506, 2005CB221404 and 2006AA05Z147), National Natural Science Foundation of China (Grant No. 20676132) and Europe Commission (SOFC 600). Also Min Yang wishes to thank Junbo Hou for useful discussion.

References (28)

  • Z.H. Bi et al.

    Solid State Ionics

    (2005)
  • Z.H. Bi et al.

    J. Power Sources

    (2006)
  • C. Clausen et al.

    Solid State Ionics

    (1994)
  • A. Mitterdorfer et al.

    Solid State Ionics

    (1998)
  • W. Zhou et al.

    J. Power Sources

    (2007)
  • M. Yang et al.

    J. Power Sources

    (2008)
  • H. Inaba et al.

    Solid State Ionics

    (1996)
  • G.Ch. Kostogloudis et al.

    Solid State Ionics

    (2000)
  • L.-W. Tai et al.

    Solid State Ionics

    (1995)
  • L.-W. Tai et al.

    Solid State Ionics

    (1995)
  • S. Li et al.

    J. Phys. Chem. Solids

    (2007)
  • N. Trofimenko et al.

    Solid State Ionics

    (1999)
  • S. Carter et al.

    Solid State Ionics

    (1992)
  • S.P.S. Badwal et al.

    Ceram. Int.

    (2001)
  • Cited by (0)

    View full text