High-Performance Flexible Aluminum–Air Batteries Enabled by a PVA–HEC Gel Electrolyte

Abstract Aluminum–air (Al–air) batteries are promising high-energy electrochemical storage systems, but the use of liquid alkaline electrolytes limits their practical implementation because of leakage, poor mechanical integrity, and electrolyte management issues. Herein, we develop a flexible three-dimensional dual-network gel polymer electrolyte (GPE) comprising poly(vinyl alcohol) (PVA), hydroxyethyl cellulose (HEC), and potassium hydroxide (KOH), in which the PVA–HEC composition and KOH concentration are systematically varied to regulate the porous network, mechanical properties, and ionic transport. The optimized G-2 formulation, containing equal amounts of PVA and HEC (2.5 g each) in 30 mL of 6 M KOH, forms a highly interconnected porous network with enhanced viscoelastic stability and electrolyte retention. The balanced PVA–HEC composition and higher KOH concentration result in an ionic conductivity of 0.26 S cm–1, substantially higher than that of the other investigated formulations (0.13 and 0.10 S cm–1), while also providing favorable interfacial charge-transfer characteristics. When integrated into a flexible Al–air cell with a Pt/C-coated Ni-foam air cathode, the G-2 electrolyte delivers a specific discharge capacity of 837.5 mA h g–1 and an energy density of 670 ± 4.56 Wh kg–1 at 3 mA cm–2. Furthermore, the cell maintains stable charge–discharge operation for 52 cycles under the applied cycling protocol. The combination of high ionic conductivity, mechanically robust gel structure, electrolyte retention, and flexible cell integration demonstrates a practical strategy for replacing leakage-prone liquid electrolytes in Al–air batteries. This work advances polymer-electrolyte-based Al–air systems by demonstrating that compositional control of a PVA–HEC dual-network can simultaneously address ionic transport and mechanical stability, providing a scalable platform for flexible and leakage-resistant energy-storage devices.