Zn-dominated interphase inhibits the anodic parasitic reactions for Al-air batteries using Zn²⁺@Agar hydrogel membrane

Flexible Al-air batteries are seen as the next generation of power devices for portable electronics due to the high capacity, low cost and environmental friendliness. However, the anodic parasitic reactions hinder their commercialization. Here, we develop a Zn²⁺@Agar hydrogel membrane for flexible Al-air battery, whose formed Zn-dominated interphase can inhibit hydrogen evolution and passivation of the Al anode, improving the discharge performance of the battery. The results show that the hydrogen evolution rate of Al anode is as low as 1.65 × 10⁻² mg cm⁻²s⁻¹ when 0.5 M Zn²⁺ are contained in the membrane, and the passivation layer of Al₂O₃ is also broken by Zn-dominated interphase. Al-air battery with this membrane has a high capacity of 2592 mAh g⁻¹, specific energy of 2847 mWh g⁻¹ and anode utilization ratio of 86.98% at 10 mA cm⁻² at 25 °C, and the battery has a high capacity of 2286 mAh g⁻¹, specific energy of 2084 mWh g⁻¹ and anode utilization ratio of 76.71% at 0 °C. Furthermore, the mechanism of interaction between single chain agar molecule and anode surface is revealed, which greatly promotes the commercial application for flexible Al-air batteries using Zn²⁺@Agar hydrogel membrane.