Nucleophilic Redox Shuttle Surpasses the Efficiency Limitation of Oxygen Redox Electrochemistry

Oxygen redox is a promising route for high-energy-density electrochemical systems, but poor oxygen evolution reaction (OER) kinetics and bubble desorption at the gas-liquid-solid interface limit efficiency and stability. Here, the introduction of a reversible nucleophilic electrochemistry embedded in the oxygen redox reaction, known as the nucleophilic redox shuttle (NRS), is reported to develop a strategy that surpasses the energy efficiency limitations of pure oxygen redox. By incorporating the miscible ionic liquid 1-(3-aminopropyl)imidazole (APMID) into Zn-air batteries (ZABs), the OER during charging is replaced by a nucleophilic oxidation reaction (NOR) with lower free-energy barriers. This pathway boosts the cycling energy efficiency from 63.2% to 80.1%, surpassing most oxygen redox-based systems. Additionally, a Zn@Cu anode is used to restore nucleophiles during charging, maintaining a low voltage gap of 0.30 V (compared to ≈0.69 V for common ZABs) over 2100 h of cycling at 1 mA·cm^-2. The high reversibility of the nucleophilic reactions ensures its stable operation even in gel electrolyte, demonstrated by the integration with a wearable patch electrocardiogram detection. These findings establish NRS as a robust strategy to extend the efficiency and durability of oxygen redox systems, advancing their practical application in next-generation energy storage.