Zinc-silver oxide and related cells

200 W/kg. Road tests with small passenger vehicles have achieved ranges of 100-230 km on a single charge. 

The zinc-silver oxide couple has been known for over 100 years and forms one of the highest energy aqueous cells. The theoretical energy density is 300 Wh/kg (1400 Wh/dm3) and practical values in the range 40-110 Wh/ kg (116-320 Wh/dm3) have been achieved. Primary cells were considered briefly in Chapter 3. 

While there are a number of methods used for manufacturing the positive electrodes, the two most important processes are the sintering of silver powders and slurry pasting. The former procedure produces electrodes with superior mechanical properties. The silver mass which is formed by 

The separator assembly is the most critical component of zinc-silver oxide secondary cells. In addition to its normal function of preventing contact and short circuit between electrodes of different polarity, a separator in this system must also  

In addition, the separator must have a low electrical resistance, good thermal and chemical stability and must be light in order to retain the high energy density characteristics of the cell. Practical separators have a composite multilayer configuration. A silver-stopping layer of cellophane or non-woven synthetic polyamide is located next to the positive electrode which reduces soluble silver species back to the metal. A potassium titanate paper layer may be placed next to the zinc electrode, and a number of cellophane layers which swell in aqueous KOH make up the middle section. In most cells the separators are fabricated as envelopes or sacks which completely enclose the zinc electrodes. 

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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. 

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