Development of electrospun and casted poly(vinyl alcohol)/poly(acrylic acid) membranes and their effect on the performance of rechargeable zinc-air batteries

Electrolytes play a major role in the cyclability of rechargeable zinc-air batteries (RZABs); thus, electrode/electrolyte interface engineering using gel polymer electrolytes (GPEs) is an attractive solution. In this study, we developed thin poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) GPEs by electrospinning and solvent casting, and their performances were compared to analyze the textural characteristics of the synthesized GPEs. For this purpose, the use of chemical crosslinkers has been avoided because of their harmful impact on the environment. Instead, three crosslinking temperatures were evaluated: 120, 140, and 160 °C, maintaining a similar thickness for all membranes (90 ± 7 μm). The highest KOH uptake was obtained with the cast GPEs, and at 120 °C, the KOH uptake was 555% versus 477% for the electrospun (ES) GPE. Nonetheless, the ionic conductivity and ion-exchange capacities increased with increasing crosslinking temperature, and the values displayed by the electrospun GPEs were higher than those for the cast materials (PVA/PAA ES 160 °C = 105.4 mS cm⁻¹, 2.4 mmol g⁻¹). Additionally, the ES GPEs were more stable, displaying no shifts in FT-IR signals after 12 months of immersion in deionized water (cast GPEs deteriorated after 5 months). The battery performance increased with increasing crosslinking temperature, achieving higher activity with GPEs at 160 °C. The battery voltage was slightly higher for the cast GPE (1.42 vs. 1.39 V), but the power density was higher for the RZAB operated with the ES GPE (148 vs. 115 mW cm⁻²), which was related to the enhanced mass transport. In addition, this GPE can operate for more than 120 charge/discharge cycles with a final round trip of 66.5%.

Graphical abstract