The Decomposition of AgO in Alkaline Solutions

Abstract

The gassing rate, r , of powder normalAgO samples, made by the chemical oxidation of AgNO3 , was measured in gassing pipettes. The mean r of 52 normalAgO samples at 200 hr false(normalAgO content≥95%,r200≤35µl/normalday/normalgfalse) was 23.0 µl/day/g. Gassing rates at different times and in different solutions, respectively, are correlated. r increased with increasing normalNaOH concentration, temperature, and pelletizing pressure, and with ball milling, r of normalAgO samples made in the presence of transition elements (added as compounds) were, in general, larger than r of samples with nontransition elements. The effect of Co and Ni is especially catastrophic. Pb suppressed r of highly gassing normalAgO samples regardless of the method of addition.

Decomposition Kinetics of AgO Cathode Material by Thermogravimetry

“…The rate of decomposition by reactions [11] and [12] was shown to increase rapidly at higher hydroxide concentrations (13). Thus, the widely varying stability among samples in this study, and also reported in the literature, may be attributed to various impurities in the sample that cause a decrease in the activation energy barrier for the AgO decomposition reaction.…”

“…The Ea values for the chemically prepared samples (126-133 k J/ real) are in excellent agreement with those reported by Nagy et al (10) for the dry decomposition (nucleation process) for AgO (133 k J/real) and by Stehlik (11) for AgO decomposition in dry air (125 k J/real). Most of the other Ea values reported for chemically prepared samples were obtained from gassing studies of AgO in KOH solutions, e.g., the 108 and 119 kJ/mol reported by Tvarusko (12) and Ruetschi (13), respectively. In a recent isothermal TG study of chemically prepared material, Tissot (14) reported Ea values ranging from 100 -+ 7 to 120 -+ 8 k J/real, depending on the AgO preparation method.…”

“…Several possible causes for the high instability of AgO found in many silver oxide cathode samples have been reported. One cause is the presence of catalytic amounts of various inorganic, mainly transition metal, impurities (12). Another possible cause is catalysis by residual KOH remaining on the material as the result of incomplete washing.…”

Primary Batteries 1951–1976

“…Amlie and Ruetschi (31) found Cd and Zn additions decreased the decomposition rate. Tvarusko (32) reported that Ni and Co additives increase the rate of decomposition while Cd, Zn, A1, and Pb decrease the rate of decomposition. He also found that stability depended on the mode of preparation of AgO.…”

Optimization of the Amount of Additives to AgO Cathodes on High-Drain Pulse Performance of Zn/AgO Cells

“…[8][9][10][11][12][13] It is known that AgO becomes unstable in an alkaline electrolyte after it has been ballmilled or pelletized. 14,15 In addition to their instability, Zn/AgO cells also cannot be used in watches and similar devices because of their two-step discharge curve. In fact, one-step cells were fabricated by both Rayovac 16,17 and Varta 18 for many years and were a major article of commerce.…”