Recently, silver-zinc (AgZn) rechargeable batteries have become commercially available in small sizes which have greater capacity and energy densities over comparatively sized rechargeable Li-ion and Li-polymer batteries. Silver-zinc batteries typically do not utilize 100% of their stored capacity; therefore, an accurate charging procedure needs to be employed to prevent overcharging and undercharging events. Charging the cell properly will increase the performance and cycle life. However, charging a cell without a battery management system is a considerable challenge since it is normally required to determine the state of charge of the battery accurately. This work provides a new robust charge algorithm which utilizes a two-zone charging approach. Silver-zinc rechargeable batteries have two voltage plateaus during discharge (Figure 1). Zone 1 is utilized when the cell is discharging in the lower plateau prior to charge (OCV~1.59V). Zone 2 is utilized when the cell was discharging in the upper plateau or transition zone prior to charge (OCV~1.82V). The cell is charged using a CC-CV (constant current-constant voltage) algorithm with a maximum charge current and a maximum charge voltage. Also, the use of additives in different electrolytes was explored and characterized with respect to increasing electrode utilization, charge rate capability, and cycle life improvement in silver-zinc rechargeable button cell batteries.

Figure 1: Discharge voltage profile for Silver-Zinc button cell batteries