Composite Polymer Anion Exchange Membranes with Sandwich Structure and Improved Performance for Zn-Air Battery

In this study, we fabricated a composite polymer anion exchange membrane (AEM) with a sandwich structure. This prepared AEM demonstrated high ionic conductivity (0.25 Scm^-1), excellent alkali resistance (8 M KOH), and good mechanical properties (tensile strength of 0.455 MPa and elongation at break of 82.13%). Here, degrease cotton (DC) treated with LiOH/urea aqueous solution was used and immersed into a coagulation bath to form a film. This film was immersed in acrylic acid (AA) monomers, and in-suit polymerization was carried out in the presence of KOH and an initiator. Finally, a composite polymer membrane with sandwich structure was achieved, in which the upper and bottom layers were mainly composed of polymerized AA (PAA) while the central layer was mainly composed of DC derived film. The central layer acted as a skeleton to improve the mechanical properties and alkali resistance. The top and bottom layers (PAA-rich layers) acted as OH- ion transport carriers, making basic cations migrate along the main chain of PAA. This newly developed composite membrane showed increased tensile strength and an elongation at break of 2.7 and 1.5 times, respectively, when compared to a control PAA/KOH AEM film. Furthermore, an electrochemical stability window of 2.0 V was measured via the cyclic voltammetry curve test, showing a wide electrochemical window and promising application in Zn-Air batteries.