Na ion- Conducting Ceramic as Solid Electrolyte for Rechargeable Seawater Batteries

[Display omitted] •Rechargeable seawater batteries are assembled using two Na+ conducting ceramics.•The battery with β″-Al2O3 electrolyte is irreversible even at 1 cycle.•The battery with NASICON shows a coulombic efficiency of 91% after 20 cycles.•NASICON is much more stable in seawater than β″-Al2O3. This study describes the assembly of a rechargeable seawater battery using hard carbon as the anode, seawater as the cathode, and a fast Na ion-conducting ceramic as the solid electrolyte. Two different Na ion-conducting ceramics, β″-Al2O3 and Na3Zr2Si2PO12 (NASICON), are used as the solid electrolytes in this study. The discharge capacity of the seawater battery with the NASICON solid electrolyte is 120mAhg−1 after the first cycle and over 91% coulombic efficiency after twenty cycles. However, under the same experimental conditions, the discharge capacity of the seawater battery with a β"-Al2O3 electrolyte significantly drops to 10mAhg−1 after one cycle. It is observed that the stability of NASICON in seawater is superior to that of β"-Al2O3 and impedance results of NASICON are not changed significantly compared to that of β"-Al2O3 after cycling tests. The stability of Na ion-conducting ceramics in seawater and their effects on the electrochemical performance of seawater batteries are presented and discussed.