Nickel hydrogen, secondary applications

Nickel—hydrogen batteries offer long cycle life that exceeds that of other maintenance-free secondary battery systems and accordingly makes it suitable for many space applications. Three types of separator materials have been used for aerospace Ni—H2 cells— asbestos (fuel-cell-grade asbestos paper), Zircar (untreated knit ZYK-15 Zircar cloth),and nylon. 

As with the primary battery systems, significant performance improvements have been made with the older secondary battery systems, and a number of newer types, such as the silver-zinc, the nickel-zinc, nickel-hydrogen, and lithium ion batteries, and the high-temperature system, have been introduced into commercial use or are under advanced development. Much of the development work on new systems has been supported by the need for high-performance batteries for portable consumer electronic applications and electric vehicles. Figure 22.1 illustrates the advances achieved in and the projections of the performance of rechargeable batteries for portable applications. 

Of the conventional secondary systems, the nickel-iron and the vented pocket-type nickel-cadmium batteries are best with regard to cycle life and total lifetime. The nickel-hydrogen battery developed mainly for aerospace applications, has demonstrated very long cycle life under shallow depth of discharge. The lead-acid batteries do not match the performance of the best alkaline batteries. The pasted cells have the shortest life of the lead-acid cells the best cycle life is obtained with the tubular design, and the Plante design has the best lifetime. 

The most expensive of the conventional-type secondary batteries are the silver batteries. Their higher cost and low cycle life have limited their use to special applications, mostly in the military and space applications, which require their high energy density. The nickel-hydrogen system is more expensive due to its pressurized design and a relatively limited production. However, their excellent cycle life under conditions of shallow discharge make them attractive for aerospace applications. The cost of cylindrical lithium ion batteries has been decreasing rapidly as production rates have increased and has recently been stated to be S1.22/Wh. ... 

Union Carbide showed the possibility of developing D-size hydrogen-nickel batteries with satisfactory performance. However, safety and cost considerations have restricted the applications of such units and the discovery of hydrogen storage alloys led to the development of the nickel-metal hydride secondary cell which was described in Chapter 6. 

Hydrogen evolution can also be prevented, and thus the unwanted secondary reactions hydrogen evolution and grid corrosion that disturb the internal oxygen cycle in lead-acid batteries, as shown in Fig. 1.25, are not present in nickel/cadmium batteries, which therefore can be hermetically sealed so that neither vapor or gas escapes from the battery. This is the reason for the market success of these batteries in the field of portable applications. 

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