Fiber nickel-cadmium battery

TABLE 26.5 Characteristics of Typical Fiber Nickel Cadmium Batteries... 

Zirconia fiber cloths, such as those made by the relic process (see Chapter 8), are used as separators in aerospace nickel-hydrogen and nickel-cadmium batteries [9j. These fibers display a high resistance to many corrosive media, including hot potassium hydroxide. Zirconia fiber felts are also present in aerospace solid oxide fuel cells. 

Application of absorbent-glass-mat separators (AGM) that are soaked by the acid so that liquid acid is not left within the cell. In alkaline electrolyte, polyamide or polypropylene fibers form corresponding mats that are used, for example, in sealed nickel/cadmium batteries (Section 1.8.2.2). 

The internal oxygen cycle, formed by oxygen evolution at the nickel-hydroxide electrode and its subsequent reduction at the cadmium electrode, was already detected in the 1940s as a possibility to avoid gas escape during overcharging, and the sealed nickel/cadmium battery appeared on the market in the 1950s. Immobilization of the alkaline electrolyte is achieved by absorption in mats of fibers of polyamide or polypropylene. Formation of a gel, as described in Section... 

FIGURE 26.4 Partial cut-away view of fiber nickel-cadmium (FNC) cell. (Source Hop-pecke Batteries.)... 

The memory effect—the tendency of a battery to adjust its electrical properties to a certain duty cycle to which it has been subjected for an extended period of time—has been a problem with nickel-cadmium batteries in some applications. Pocket, fiber, and plastic-bonded plate cells do not show this tendency. See Sec. 27.7.2 for a description of the memory effect with sintered-plate nickel-cadmium batteries. 

FIGURE 28.5 Sealed rectangular nickel-cadmium battery using fiber-structured electrodes. Courtesy of Hoppecke Batteries.)... 

The nickel-based batteries are nickel-iron, nickel-cadmium, nickel-hydrogen, and nickel-zinc, and the separators are simple absorbent materials. The nickel-cadmium vented battery use nonwoven nylon felt. Nonwoven fibers of PE or PP are used in the sealed version, where gaseous oxygen permeability is an essential feature of a separator. 

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