With reference to FIG. 20D, there is shown the experimental results of galvanostatic charge/discharge testing on Zn-air batteries at 2 mA cm^?2 with each cycle being 12 min. A short interval (1 min) between charge and discharge can diagnose the rechargeability and alleviate irreversible side reactions. The battery was cycled 160 h (=800 cycles) without visible voltage change, indicative of the excellent stability of the battery. Initially, the charge and discharge voltages are about 1.97 and 1.29 V (corresponding to charge/discharge overpotential of 0.68 V with a round-trip efficiency of 65.5%). After 800 cycles over a long time of 160 h, the charge and discharge voltages slightly change to 2.02 and 1.2 V (i.e., charge/discharge overpotential of 0.84 V with a round-trip efficiency of 59.4%). Such excellent cycling stability over this long time-scale is even better than that of Zn-air batteries in the tri-electrode systems being tested. In contrast, referring to FIG. 23, the rechargeable Zn-air battery with the PVA electrolyte shows much inferior performances. During merely 80 cycles (=16 h), the charge voltage greatly increases from the initial 2.02 V to 2.73 V, and the discharge voltage dramatically decreases from the initial 1.22 V to 0.8 V.

With reference to FIG. 24, after cycle for 70 h, the air cathode was removed and left the PANa polyelectrolyte fully exposed in air for 17 h. Then the same air cathode was paved on the electrolyte and continued to cycle the same battery for an additional 13 h.