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

Abstract

AbstractRechargeable 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.