All-Solid-State Na-O₂Batteries 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.