Planar-Bipolar Stacking

Planar-bipolar stacks can be further characterized according to arrangement of the gas flow ... 

In a planar SOFC stack, the bipolar plates are usually made of chromium-containing stainless steel. At high temperature, this steel is covered by a thin oxide film of Cr203, which reacts with traces of water to form volatile Crcathode catalyst layer, which in the SOFC community is called the Junctional layer (FL). In the FL, VCH is reduced electrochemically with the deposition of solid Cr203 ... 

A bipolar version of the tank cell design, the Bipolar Stack cell (25). consists of an assembly of parallel, planar electrodes separate by insulating spacers. Flow of electrolyte between electrodes may be either by natural or forced circulation. This design of cell is easy to construct since it simply comprises a Stacie of alternating electrodes and spacers with electrical... 

The most common fuel cell stack design is the so-called planar-bipolar arrangement (Figure 1-2 depicts a PAFC). Individual unit cells are electrically connected with interconnects. Because of the configuration of a flat plate cell, the interconnect becomes a separator plate with two functions ... 

PEFC stacks are almost universally of the planar bipolar type. Typically, the electrodes are cast as thin films that are either transferred to the membrane or applied directly to the membrane. Alternatively, the catalyst-electrode layer may be deposited onto the backing layer, then bonded to the membrane. 

Fig. 1.2 Principles, functions and schematic of a flat planar SOFC where the PEN is stacked between two bipolar plates (interconnect with gas flow fields).

The design of BP for PEMFCs is dependent on the cell architecture, on the fuel to be used, and on the method of stack cooling (e.g., water or air-cooling). To date, most of the fuel cells have employed traditional filter-press architecture, so that the cells are planar and reactant flow distribution to the cells is provided by the bipolar plate. The bipolar plate therefore incorporates reactant channels machined or etched into the surface. These supply the fuel and oxidant and also provide... 

Each cell in this planar stack is connected in series, that is, the positive electrode of one cell is connected to the negative of the next cell and so on. In a block stack this is accomplished by using bipolar plates, but in the L79 we use circuit board traces with tab wire connects to perform the same function as the bipolar plates. The L79 can also be built in a parallel configuration or a series-parallel configuration depending on the current and voltage desired. 

The battery stack consists of cells formed by bipolar planar electrodes made of conducting ( 1 cm ) carbon-plastic com-... 

Figure 6.47 Planar stack design with open cathode design for natural breathing. Note the use of cell-to-cell interconnects instead of structural bipolar plates common to PEFC designs.

Development of small fuel cells for portable power applications has resulted in a myriad of stack configurations. Some stacks are miniaturized replicas of the larger automotive or stationary power fuel cells with the same components, MEAs, gas diffusion layers, bipolar plates, and end plates. Some use planar configuration where the cells are connected with conductive strips. Recently, microfluidic cells manufactured on silicon-based chips are emerging [37,38]. 

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