Enhanced zinc reversibility enabled by zinc–bromide complexation of a quasi-solid electrolyte for high-performance flexible zinc–air batteries

Abstract

Flexible zinc–air batteries (FZABs) have shown great promise for wearable electronic devices owing to their high energy density, safety, and environmental benignity. However, the key quasi-solid electrolyte materials with high ionic conductivity, strong mechanical strength, and high Zn anode stability are still limited, posing great challenges to cell lifetime. Herein, cross-linked dual-network quasi-solid electrolytes composed of soft polyacrylamide (PAM) and rigid chitosan (CS) polymers functionalized with aluminum-based bentonite (BT) and potassium bromide (KBr) (PAM/CS-BT-KBr) are fabricated. Notably, the addition of KBr initiates a solid–liquid reaction with excellent kinetics and reversibility due to the formation of Zn–Br complexes, which effectively avoids passivation of ZnO and suppresses Zn dendrite growth. Additionally, the PAM/CS-BT-KBr shows both high tensile strength and toughness (710% stretchability and 210 kPa stress) due to the synergistic effect of BT, PAM and CS, which promotes covalent and hydrogen bonding interactions in the system. The electrolyte also exhibits ultrahigh ionic conductivity (110.5 mS cm⁻¹) with the existence of –OH groups and interconnected channels in BT, as well as a porous structure with high hydrophilicity. Building on these excellent material properties, FZABs are fabricated with high power density (153 mW cm⁻²) and long lifespan (150 h), as well as good flexibility, manifesting their great potential applications in wearable electronics.