Effect of temperature and charge stand on electrochemical performance of silver oxide–zinc cell

Abstract

It is known that the storage conditions influence the performance of a battery. The effect of temperature on the discharge capacity of silver oxide–zinc (AgO–Zn) cells is investigated quantitatively in the present study. 40Ah silver oxide–zinc cells are charged in two step constant current mode up to 2.05V and stored at temperatures in the range of −20°C to 60°C for charge stand periods of 1 day, 7 days and 15 days. Subsequently, the cells are discharged at 1C rate current until voltages of each cell reached 1.2V. Although the discharge capacity of these cells at and around room temperature is reasonable, at temperatures below 0°C the performance is poor. From 40°C to 60°C temperatures, the discharge capacities decreased with charge stand periods. The discharge capacities are not affected by the charge stand periods from −20°C to 30°C. Best performances in terms of the capacity and average midpoint voltage for different charge stand periods are obtained at 30°C. To identify the reasons for the poor performance at sub-ambient temperatures, electrochemical impedance studies are carried out on a fresh cell. The impedance data are analyzed using an equivalent circuit by Zman fitting software and the impedance parameters are evaluated. The resistances corresponding to mid-frequencies and low frequencies of Nyquist impedance plot exhibit a strong dependence on temperatures. The kinetic parameter namely, apparent exchange current density is calculated and discussed.