High-Performance Quasi-Solid-State Na-Air Battery via Gel Cathode by Confining Moisture

Rechargeable Na-air batteries are the subject of great interest because of their high theoretical specific energy density, lower cost, and lower charge potential compared with Li-air batteries. However, high purity O₂ as a working environment is required to achieve high-performance Na-air batteries, which obstructs their application as a high-energy-density battery. Although aqueous Na-air batteries can operate in ambient air, long cycle and high safety remain challenges for aqueous Na-air batteries because the aqueous electrolyte is volatile. Here, a quasi-solid-state Na-air battery is reported by utilizing a gel cathode, which is composed of single-walled carbon nanotubes and room-temperature ionic liquids, achieving high safety and long cycling life of 125 cycles (528 h) at a current density of 0.1 mA cm⁻², which is surprisingly better than that of quasi-solid-state Na O₂ batteries. In situ XRD characterizations reveal that water in ambient air is gradually deposited on the surface of the gel cathode to form a water layer, which facilitates the generation of soluble discharge product of NaOH thermodynamically with high conductivity. This work shall be critical to develop and promote the practical application of Na-air batteries, opening a new way to the design of solid-state metal-air batteries.