Characterization of a new rechargeable Zn/PVA-KOH/Bi2O3 battery: structural changes of the Bi2O3 electrode

Abstract

In this study, bismuth oxide is utilized as positive electrode in a rechargeable Zn-based battery using a gel polymer electrolyte. Bi₂O₃ is reduced to Bi metal during the discharge process of the Zn/PVA-KOH/Bi₂O₃ battery, obtaining efficiencies higher than 90% from the Bi₂O₃ mass initially used for discharge currents ≤10 mA. During the charge process, Bi metal is oxidized to recover the Bi₂O₃. A great number of charge/discharge cycles are performed for a single battery and for two batteries connected in series. This battery develops coulombic efficiencies of 100% for more than 100 cycles and energy efficiencies higher than 80% after 80 cycles. XRD, AES and XPS measurements demonstrate the formation of Bi metal during the discharge and the build-up of Bi₂O₃ structure during the charge. Besides, SEM and EDX techniques confirm the structural changes observed during the reduction and oxidation processes. Finally, discharge and charge mechanisms of the Bi₂O₃ electrode tested on a Zn/PVA-KOH/Bi₂O₃ battery are discussed.