Solid oxide fuel cells thickness

The tape-casting method makes possible the fabrication of films in the region of several hundred micrometers thick. The mechanical strength allows the use of such a solid electrolyte as the structural element for devices such as the high-temperature solid oxide fuel cell in which zirconia-based solid electrolytes are employed both as electrolyte and as mechanical separator of the electrodes. 

Y.-S. Chou and J.W. Stevenson, Phlogopite Mica-Based Compressive Seals for Solid Oxide Fuel Cells Effect of Mica Thickness, Journal of Power Sources, 124, pp. 473 178 (2003). 

Figure 30 shows the enlarged cross section of a solid oxide fuel cell composed of a 50- to 100-/im-thick Zr02 membrane, a relatively thick (—100 gm) porous cathode, and a porous Ni/Zr02 cermet anode. 

Chan S.H., Khor K.A., Xia Z.T., 2001. A complete polarization model of a solid oxide fuel cell and its sensitivity to the change of cell components thickness. Journal of Power Sources 93, 130-140. 

In the case of a solid oxide fuel cell, the anode or cathode support can be relatively thin because the component does not need to bear a very high load. However, in the case of oxygen transport membranes, the porous support needs to withstand a differential pressure of 20 atm or greater. Therefore, porous supports which are several millimeters thick are often considered. Alternatively, other concepts for strengthening the support structure are considered. These can include internal structures such as multichannel tubes, distinct solid porous inserts in tubes [21] and support braces in planar geometries. Examples of such structures are shown in Fig. 6.5 and 6.6. 

Solid oxide fuel cells (SOFCs) are one of the most efficient energy conversion devices [1]. The main demand in the current SOFC development is lowering operation temperature to the range of 600-800 C - intermediate temperature SOFC (IT-SOFC). In order to lower operational temperature and increase or at least sustain performance comparable to that at high temperature SOFCs, it is necessary to decrease the resistance of the electrolyte and lower the overpotential of the electrodes. One of the ways to achieve this goal is to decrease the thickness of the electrolyte and optimize the structure of the electrodes. 

Trunec has described the thermoplastic extrusion of thin-wall tubes made of yttria-stabilized zirconia and gadolinia-doped ceria [Tru 04], These ceramics are used for solid oxide electrolyte applications, e.g. solid oxide fuel cells. The thermoplastic binder system used consists of ethylene-vinyl acetate copolymer, parafHn wax and stearic acid. With this system tubes with an outer diameter of 10.5 mm and wall thicknesses of 290 and 280 pm could be fabricated. 

Planar solid oxide fuel cells are built analogously to other kinds of fuel cells, such as polymer electrolyte fuel cells. Usually, one of the electrodes (the fuel anode or the oxygen cathode) serves as support for the membrane-electrode assembly. To this end, it is relatively thick (up to 2 mm), and thin layers of the electrolyte and... 

G. Robert, A. Kaiser, K. Honegger and E. Batawi, Anode Supported Solid Oxide Fuel Cells with a Thick Anode Substrate, Proc. 5" European SOFC Forum, (Ed. J. Huijsmans), Lucerne, Switzerland, p. 116 (2002)... 

Viscoelastic inks for direct-write microfabrication of single-chamber micro solid oxide fuel cells with coplanar thick electrodes. Mater. Res. Soc. Symp. Proc., 1179, 111-116. 

At small s, the Tafel region disappears and the transition region directly links the linear and double-Tafel domains (Figure 23.2b). This situation is typical of a thick solid oxide fuel cell (SOFC) anode (anode-supported design). For such an anode, k is large and e is small, which corresponds to the polarization curve in Figure 23.2b. The well-known hnearity of a SOFC polarization curve means that the anode operates below the transition region. 

Solid Oxide Fuel Cells, Thermodynamics, Fig. 3 Themodynamic theoretical conversion efficiency for reforming SOFC and further lowering in efficiency due to the Joule loss and electrochemical oxygen permeation through the YSZ electrolyte for difference thickness... 

Metal Supported-Solid Oxide Fuel Cells (MS-SOFC) represent a promising new design for fuel cells which may overcome the limitations of anode-supported cells (such as poor thermal cycling resistance and brittleness. Nickel phase re-oxidation upon exposure to transient uncontrolled conditions) due to the much better mechanical properties of the support that is represented by a porous thick metal substrate, the thickness of the ceramic layers (anode/electrolyte/cathode) being in the order of 10-50 pm, only. In addition, in this design (Fig. 1), the replacement of the thick Ni/YSZ cermet with ferritic stainless steel leads to several benefits in term of fabrication cost and safety. 

Xue, Y.J., Miao, H., He, C.R., Wang, J.X., Liu, M., Sun, S.S., Wang, Q., and Wang, W.G. (2015) Electrolyte supported solid oxide fuel cells with the super large size and thin ytterbia stabilized zirconia substrate. /. Power Sources, 279, 610-619. Joo, XJ.H. and Choi, G.M. (2008) Thick-film electrolyte (thickness <20pm)-supported solid oxide fuel cells. /. Power Sources, 180 (1), 195-198. 

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