A completely sealed high temperature carbon-air battery with carbon dioxide absorber

A completely sealed high temperature carbon-air battery is proposed and prepared using a tubular oxygen-ion-conducting yttrium stabilized zirconia electrolyte with anode inside and cathode outside. CaO and carbon powders, with a molar ratio of 0.5, 0.75, and 1.0, are respectively loaded in the anode chamber, in two ways: One is mixing CaO and C together (mixing mode) and the other is loading them one by one (separating mode). The electrochemical output performance and discharging time of the batteries increase with decreasing CaO/C ratio. Thermodynamic calculation results show that the pressure of the anode chamber of a battery increases with more carbon oxidized. CO₂ produced through the electrochemical oxidation of carbon can be absorbed by CaO to produce CaCO₃, resulting in relieve of pressure. However, insufficient CO₂ for maintaining the operation of battery is also caused by CaO. This evidence may be mitigated by loading C and CaO separately to avoid immediate reaction between CO₂ and CaO. A carbon-air battery with 0.25 g carbon powder separately loaded with CaO in a CaO/C ratio of 0.5 discharges at 200 mA for 6.9 h, giving a practical specific energy density of 1300 Wh kg⁻¹, considering the mass of both C and CaO.