Development of quaternized poly(vinyl alcohol)/chitosan/two-dimensional molybdenum disulfide anion exchange membrane as a separator for electrochemical processes

In response to the global shift toward the expansion of large-scale energy storage systems (ESSs), secondary zinc-air batteries (ZABs) have attracted significant attention as promising candidates for next-generation batteries due to their high energy density, cost-effectiveness, and safety. However, their long-term practical application is hindered by several challenges associated with the membrane separator, including the formation of resistive zinc oxide layers and low hydroxide-ion conductivity. These limitations are attributed to poor ion-selectivity, which impedes electrochemical reactions and degrades battery performance. To address these issues, this study developed a series of innovative membrane separators featuring quaternary ammonium (QA)-functionalized polyvinyl alcohol (PVA), chitosan (CS) particles, non-woven polypropylene (PP), and exfoliated molybdenum disulfide (MoS2). The QA-functionalized PVA significantly enhances hydroxide-ion conductivity by introducing positively charged sites that facilitate hydroxide binding and enable the formation of efficient conductive pathways under alkaline conditions. The increased density of these active sites supports faster hydroxide-ion transport within the separator. Chitosan, composed of cationic polysaccharides, exhibits strong reactivity with negatively charged species, making it an excellent component for separator fabrication. Furthermore, incorporating exfoliated MoS2 sheets into the QA-functionalized PVA matrix resulted in a stable composite separator with exceptional performance, achieving a conductivity of 87.3 mS cm-1 and demonstrating prolonged cycling stability exceeding 465 cycles. This improved selectivity is attributed to the formation of efficient ion-transport pathways, while enhanced stability stems from the physical characteristics of MoS2 and its electrostatic interactions. Compared to existing technologies, the developed separators present a highly promising solution for advancing ZAB performance in large-scale energy storage applications.