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

Xiaoxia Cai,Guotao Zhang,Yuansong Zhang,Qiang Wang,Xian Zhang,Fuzhong Wang,Xiaotao Wang,Cong Li

doi:10.3390/membranes11030224

Xiaoxia Cai, Guotao Zhang + Show 6 more

Open Access

https://doi.org/10.3390/membranes11030224

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Abstract

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.

Highlights

Because of their high specific capacity, high energy density, stable discharge voltage, and no pollution, Zn–Air batteries have recently received enormous attention as promising green energy devices, especially as a reliable power source for portable electronics [1,2,3,4,5]
The crystallization induced low ionic conductivity (10−7 to 10−8 S cm−1 at ambient temperature) and poor mechanical properties, especially in high KOH concentration, which severely restricted the application in electrochemical devices
In order to increase ionic conductivity, a polyvinyl alcohol PVA–KOH alkaline polymer electrolyte system was developed by Lewandowski et al [13] using ac impedance and cyclic voltammetry methods, showing a conductivity about of 10−4 S cm−1 at room temperature with poor mechanical properties

Summary

Introduction

Because of their high specific capacity, high energy density, stable discharge voltage, and no pollution, Zn–Air batteries have recently received enormous attention as promising green energy devices, especially as a reliable power source for portable electronics [1,2,3,4,5]. Zn–Air batteries generally comprise Zn metal anodes, metal oxide cathodes, a potassium hydroxide (KOH)-based alkaline electrolyte solution, and separator membranes. The crystallization induced low ionic conductivity (10−7 to 10−8 S cm−1 at ambient temperature) and poor mechanical properties, especially in high KOH concentration, which severely restricted the application in electrochemical devices.

Results

Conclusion