Enhancing Electrochemical Performance of Zinc-Air Batteries Using Freeze Crosslinked Carboxymethylcellulose-Chitosan Hydrogels as Electrolytes

Abstract

Zinc-air batteries (ZABs) are devices of great interest as a replacement option for subsequent technologies to lithium-ion batteries. Still, the need for suitable electrolyte materials limits their application in commercial devices. In this study, a green hidrogel composed of chitosan and carboxymethylcellulose was synthesized with the use of citric acid as a chemical crosslinker, physical freezing-thawing, and freezing-drying strategies. Physicochemical, thermal, and electrochemical characterizations were performed to study the effects of the proposed synthesis’ on the performance of the hydrogels for the desired application. The obtained hydrogels showed a porous morphology that was doped with a 12 M KOH solution. Adequate complexation of K+ cations and the polymer chains was observed. The resulting membranes showed an enhanced ionic conductivity of 0.39 S cm‒1, attributed to the pores and channels generated by the crosslinking strategies, contributing to the pathways for ions to move easily. In addition, the temperature dependence of the conduction mechanism was confirmed in the temperature range of 0 °C to 70 °C. The electrolytes were employed in ZABs prototypes, achieving a maximum power density of 117 mW cm‒2 and a specific capacitance of 1899 mAh g‒1. The presented results show the promising properties of these hydrogels as electrolytes for green storage devices.