All-Solid-State Na–O₂ Batteries with Long Cycle Performance

All-solid-state sodium oxygen (ASS Na–O2) batteries have received interest due to their higher theoretical energy density, lower cost, higher safety level, and nonflammability compared with liquid electrolyte and Li–O2 batteries. Here, we report the application of carbon nanotube (CNT) and Ru/CNT cathodes, succinonitrile with a NaClO4 (SN + NaClO4) interlayer, a Na3Zr2Si2PO12 (NZSP) solid electrolyte, and a Na film anode for ASS Na–O2 batteries. Results showed that the SN + NaClO4 interlayer plays a crucial role in the tri-conductive cathode, ionic conductivity, and interfacial charge transfer kinetics between the Ru/CNT cathode and NZSP electrolyte. The ASS Na–O2 batteries with Ru/CNT and SN + NaClO4 tri-conductive cathodes exhibited a long cycling performance of 100 cycles (current density of 100 mA g–1 and limited capacity of 500 mA h g–1), a discharge capacity of 11 034 mA h g–1 (current density of 100 mA g–1), and a small overpotential gap of 1.4 V. These values were better than those for CNT and SN + NaClO4 tri-conductive cathodes (maximum discharge capacity of 2413 mA h g–1, 27 cycles, and potential gap of 1.7 V) with a Na2O2 discharge product. Ex situ analysis showed that the Ru/CNT cathode achieved superior reversibility deposition and decomposition of the Na2O2 discharge product. Therefore, the ASS Na–O2 battery system is safe and stable for energy storage applications.