Asymmetric Kosmotropism-Stabilized Double-Layer Hydrogel for Low-Cost Neutral Zinc-Air Battery

Zinc air battery (ZAB) provides a low-cost and high-energy density power source, particularly in wearable and portable devices. Despite the extensive research on air cathode catalysts, their practical application is hindered by low zinc utilization rate and severe corrosion and passivation in liquid-based alkaline electrolytes. Herein, a double-layer gel (DLKgel) is developed by leveraging the distinct kosmotropic properties of ZnCl₂ and ZnSO₄. Through phase separation induced by the kosmotropic differentiation (instead of membrane in decoupled systems), this DLKgel electrolyte serves a dual purpose of shielding cathode from irreversible reaction products and protecting Zn anode from passivation. Neutral ZABs with DLKgel demonstrate high zinc utilization rate of 89.3% and stable cycling over 800 h under a current density of 0.1 mA cm⁻². The integration of DLKgel-based ZABs into a flexible GPS tracking device is demonstrated, highlighting the potential for broad adoption of flexible ZABs in wearable and logistics applications.