Enhancing zinc-air battery performance through ph-tuned biopolymeric hydrogels in near-neutral electrolytes

Abstract

In light of the escalating global energy demands and the critical pursuit of sustainable energy solutions, this research delves into the electrolytic behavior of biopolymeric hydrogels derived from chitosan and starch in near-neutral ionic solutions within a ZnCl₂ + NH₄Cl system, evaluated at different pH values to enhance zinc-air battery (ZAB) performance. The study evaluates the impact of ionic solution pH on the structural, morphological, thermal, mechanical, and electrochemical properties of the hydrogels in primary ZAB prototypes. Remarkably, at a near-neutral pH of 7, the polymer gel electrolyte demonstrated superior ionic conductivity (0.11 S·cm⁻¹), specific capacity (675 mAh·g⁻¹), lower volume resistances and higher specific capacitances. Thermal analysis revealed increased stability of the polymer gel systems at elevated pH levels. This finding was corroborated by Scanning Electron Microscopy (SEM), which evidenced the presence of uniform and cohesive microstructures attributed to the formation of stable zinc-amine complexes. Fourier Transform Infrared Spectroscopy (FTIR) indicated pH-dependent variations in the vibrational bands of functional groups, influencing zinc ion interactions and electrochemical performance. X-ray diffraction (XRD) analysis revealed the absence of solid precipitates at pH 7, which enhances ionic mobility and conductivity. Consequently, the findings suggest that maintaining near neutral pH conditions substantially enhances the physical and electrochemical properties of ZAB. Hence, the proposed system constitutes a promising avenue for sustainable energy storage solutions.