Coplanar fuel cell

COPLANAR FUEL CELL DESIGN STRIP CELLS... 

In the flat mini-fuel cell battery design described in Section 17.2, strip-type electrodes are also often used (see Figure 17.1), but there, in contrast to the coplanar fuel cells described in this section, they are used in batteries with segregated reactant supply and dual-faced electrolyte membranes, with both reactants on different sides of the membrane. These two cases of using strip electrodes must not be confused. 

The main advantage of the coplanar fuel cell design is the possibility of considerably reducing the internal ohmic resistance of the cell, which is due primarily to the ohmic resistauce of the electrolyte. To decrease the ohmic resistance of conventional MEAs it is necessary to reduce the thickness of the electrolyte. An excessive reduction of this thickness can have detrimental consequences the formation of cracks and pinholes and the loss of stability and gas-tighmess. In strip cells the ohmic resistance is determined by the width of the gap between cathodes and anodes and can be decreased simply by narrowing this gap. If the electrodes are micropattemed to be close together, the cell s power density can be increased considerably. 

Another advantage of coplanar fuel cell design is that the electrolyte (which is no longer used to prevent mixing of the reactants) does not have to be a pore-free thin film. This simplifies preparation of the electrolyte and makes the cell more shock resistant against both mechanical and thermal stresses. 

For a large-scale production of coplanar fuel cells, modem processing technologies can be used, such as micromechanical system (MEMS) processing and photolithographic patterning. Thus, a sharp decrease in production costs compared with the present costs for conventional fuel cells can be anticipated. 

The test results suggest that the fuel cell seal variant which contains the coplanar waveguide structure is probably a better candidate than the microstrip variant for the goal of designing a seal that might be indicative of defects or precursors to seal failure, as the sample-to-sample variability is much greater in the microstrip variant. 

Miniaturization limits for single-chamber micro solid oxide fuel cells with coplanar electrodes. J. Power Sources, 194 (2), 941-949. 

Singlemicro solid oxide fuel cells study of anode and cathode materials in coplanar electrode design. Solid State Ionics, 181 (5-7), 332-337. 

The coplanar fuel ceU design is used primarily for fuel cells with a mixed-reactant supply. In this design both selective electrodes (anodes and cathodes) are situated on the same surface of the electrolyte (ion-conducting membrane, matrix filled with liquid electrolyte, or solid electrolyte). This surface also contacts the reactant mixture. Such an electrolyte is said to be single-faced. This is in contrast to the conventional MEAs used for almost all varieties of fuel cells, in which the electrolyte is dual-faced, contacting the anode and the fuel on one side and the cathode and the oxidizer on the other side. 

At present the coplanar design principle is used primarily for single-chamber solid-oxide fuel cells (SC-SOFCs), for which its advantages are very substantial (see Section 18.5). In the literature there are few indications of the application of this principle to other fuel cell types. 

The cell efficiency of SC-SOFCs with interdigitated electrodes was estimated to be below 1%, with a fuel utilization of less than 0.1% [63]. In addition to insufficient catalytic selectivity of the electrode materials, the small size of SC-SOFCs with coplanar electrodes limits the electrochemical conversion of fuel. 

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