Rechargeable aqueous Na-air battery & Seawater battery: Highly improved Voltage efficiency by catalysts

Abstract

Metal-air batteries are promising alternatives to the state-of-the-art Li-ion batteries owing to their high theoretical energy density. This thesis reports for the first time, a rechargeable aqueous Na-air battery, in which a Na-ion conducting ceramic separator (Na3Zr2Si2PO12) and carbon paper coated with carbon black (Vulcan) or Pt/C nanoparticles were used as a solid electrolyte and air-electrode, respectively. The Na-air cells with the air-electrode consisting of Vulcan- or Pt/C-coated carbon papers exhibited excellent rechargeability with small charge-discharge voltage gaps (voltage efficiency of 84.8 % and 97.6 %, respectively) over 18 cycles (total 180 h), compared to the cell with only the carbon paper electrode (79.0 %). These results are expected to pave the way for more cost-effective Na-air batteries with high energy density.