Zinc/silver oxide reserve batteries

Battery systems of complex design and structure using—at least for one electrode—expensive materials are (for economic reasons) mainly conceived as storage batteries. Primary (and "reserve") versions of the zinc/silver oxide battery [(-) Zn/KOH/AgO (+)] — as a first example—are only used in particular cases where the question of cost is not crucial, e.g., for marine [26-28] and space applications [29]. 

Zinc-silver oxide batteries as primary cells are known both as button cells, e.g., for hearing aids, watches, or cameras, and for military applications, usually as reserve batteries. Since the latter after activation have only a very short life (a few seconds to some minutes), a separation by cellulo-sic paper is generally sufficient. 

Zinc-silver oxide reserve batteries have application as power sources for various systems in manned and unmanned space vehicles. 

FIGURE 18.2 Zinc/silver oxide primary reserve battery designed for automatic activation. (Courtesy of Eagle-Picher Industries.)... 

At one time, the zinc/potassium hydroxide/silver oxide system was also employed in spin-dependent reserve batteries. More frequently, this reserve system has been used in nonspin applications, such as missiles, where the electrolyte is driven into place by a gas generator or other activation method (Chap. 18). This system is again finding favor in some applications where the potential hazards of lithium-based systems can create safety problems. The chemistry of the zinc/silver oxide couple can be represented by either of two reactions, depending on the oxidation state of the silver oxide ... 

Various problems related to the construction and performances of these batteries, such as changes in materials of membranes and additives both to the electrode materials and to the electrolyte, were studied in recent years. Some instability of the silver electrode during such storage period and the ways of avoiding these difficulties were studied and discussed [347]. Reserve activated silver oxide-zinc cells were constructed [348] with synthetic Ag20 and Pb-treated zinc electrodes were produced by a nonelec-trolytic process. The cells were tested before and after thermally accelerated aging. 

Operating Temperature Limits. Like most other batteries, the performance of liquid-electrolyte reserve batteries is affected by temperature. Military applications frequently demand battery operations at all temperatures between -40 and 60°C, with storage limits of -55 to 70°C. These requirements are routinely met by the lead/fluoboric acid/lead dioxide systems and, with some difficulty at the low-temperature end, by the lithium/thionyl chloride and zinc/potassium hydroxide/silver oxide systems. Provision is occasionally made to warm the electrolyte prior to the activation of the two latter systems. 

---