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

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 120 mAh g^-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 10 mAh g^-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.