Flat plate cells

Other important parts of the cell are 1) the structure for distributing the reactant gases across the electrode surface and which serves as mechanical support, shown as ribs in Figure 1-4, 2) electrolyte reservoirs for liquid electrolyte cells to replenish electrolyte lost over life, and 3) current collectors (not shown) that provide a path for the current between the electrodes and the separator of flat plate cells. Other arrangements of gas flow and current flow are used in fuel cell stack designs, and are mentioned in Sections 3 through 8 for the various type cells. 

Planar geometry Although there are variations in detail, the design of the planar or flat plate cell, and how cells are interconnected are essentially as illustrated in Fig. 4.27. The construction may involve a self-supporting, coated electrolyte or, if the operating temperature permits, the anode-electrolyte-cathode structure may be supported on a stainless steel bipolar plate. 

Flat plate cells are usually made with electrodes spread on screens or grids like lead-acid batteries or industrial Ni-Cd batteries. In these types of batteries the electrodes itself are good metallic conductors To build manganese dioxide batteries as plate cells good conductive screens would be needed. A well known example for a bipolar Mn02-Zn cell in commercial production is the 6 Volt Polaroid camera film battery, a primary battery with a weakly acidic electrolyte. 

On the other hand, in bipolar cells, only the terminal cells are connected by intercell conductors, and there are typically many unit cells electrically in series between the terminal cells (Fig. 5.2). The two basic types of bipolar cells are the flat plate cell and the finger type cell. A group of bipolar cells that have a common piping system for the fluids, via manifolds, is referred to as an electrolyzer or sometimes a series or a stack. Within a single bipolar electrolyzer, there are sometimes more than one set of terminal cells. Bipolar electrolyzers can be connected via an external bus within a DC circuit in series or in parallel, but usually not both. Furthermore, in the case of mercury-cell plant conversions to membrane cells, the electrolyzers are connected electrically in parallel as shown in Fig. 5.3. 

Li-ion polymer and flat plate cells are produced in small sizes for cellular phones (about 0.5 Ah and higher) and large sizes (up to 200 Ah) for energy storage and motive power applications. A commOTi characteristic is that the polymer separator holds the electrolyte and forms a physical barrier between the anode and cathode to prevent internal shorting. Most polymer cells are flat plate (prismatic) construction. 

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 ... 

Flat-Plate Cell A cell fabricated with rectangular flat-plate electrodes (also called a Prismatic Cell). 

Fig. 9.3 Illustration of the electrical potential distribution calculated for the flat-plate cell with ideally symmetrical working and counter electrodes, according to [25]. Solid lines correspond to the equipotential surfaces. Possible positions of reference electrodes are indicated...

Because of the high initial cost of Plantd cells, specially designed flat plate cells have been developed to provide a cheaper but shorter-lived alternative source of standby power. The layout of a typical modem flat plate cell is shown in Figure 32.2. 

Chloride Industrial Batteries also supply high-performance flat-plate cell type standby batteries in the conventional vented (types FAP-H and FCP-H) and low-maintenance (types SAP, SBP and SEP) versions. Capacities up to 600 Ah (vented. Table 50.9)... 

New separator technology has been incorporated into these flat-plate cells. The vented types incorporate separation between adjacent plates consisting of a glass wool mat and nbbed microporous PVC. The glass wool mats are fitted against the positive plates and act as an effective retainer of the positive active material. The low-resistance separators, which ai inert... 

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