Poly(acrylic acid) Cross-Linked with Potassium As Gel Polymer Electrolyte in Small Zinc-Air Batteries

Abstract

Zn-air batteries are considered as a suitable alternative to typical batteries due to the zinc is a highly abundant and environmentally friendly material (exist more than 224 trillions of tons in the first mile of deep). However, zinc anode has several challenges to overcome such as shape changes, dendritic growth, passivation, and corrosion. Two strategies can be followed to decrease/eliminate these issues, one of them consists in the metallic electrode modification, and other in the electrolyte modification. In this work, poly(acrylic acid) cross-linked with potassium (PAAK) was used to develop gel polymer electrolytes (GPEs) in 6 M KOH with and without additives (CTAB), testing their effect on battery performances. PAAK at different weight percentages were evaluated, being 3 wt.% PAAK the most promising concentration displaying a battery performance similar to that displayed by an aqueous 6 M KOH solution (20 mW cm-2). Furthermore, SEM images after a discharge experiment for 4 h at 1.25 mA cm-2 followed by a charge process indicated that the zinc anode maintained its original shape (nanoflakes with thickness of tens of nanometers) in the Zn-air battery operated with the GPE. However, zinc anode suffered shape changes in the 6 M KOH aqueous electrolyte, forming hemispherical particles with sizes between 1 to 4 μm. Also, the battery tests with the GPE displayed a higher durability to that operated with 6 M KOH aqueous electrolyte.