Development of Polymer Composite Membrane Electrolytes in Alkaline Zn/MnO₂, Al/MnO₂, Zinc/Air, and Al/Air Electrochemical Cells

This paper reports on the novel composite membrane electrolytes used in Zn/MnO₂, Al/MnO₂, Al/air, and zinc/air electrochemical devices. The composite membranes were made using poly(vinyl alcohol), poly(acrylic acid), and a sulfonated polypropylene/polyethylene separator to enhance the electrochemical characteristics and dimensional stability of the solid electrolyte membranes. The ionic conductivity was improved significantly by the amount of acrylic acid incorporated into the polymer systems. In general, the ionic conductivity was also enhanced gradually as the testing temperature increased from 20 to 80 °C. Porous zinc gel electrodes and pure aluminum plates were used as the anodes, while porous carbon air electrodes or porous MnO₂ electrodes were used as the cathodes. The cyclic voltammetry properties and electrochemical impedance characteristics were investigated to evaluate the cell behavior and electrochemical properties of these prototype cells. The results showed that these prototype cells had a low bulk resistance, a high cell power density, and a unique device stability. The Al/MnO₂ cell achieved a density of 110 mW cm^-2 at the designated current density for the discharge tests, while the other cells also exhibited good values in the range of 70-100 mW cm^-2. Furthermore, the Zn/air cell consisting of the PVA/PAA = 10:5 composite membrane revealed an excellent discharge capacity of 1507 mAh. This represented a very high anode utilization of 95.7% at the C/10 rate.