2025-05-27 マサチューセッツ工科大学（MIT）
＜関連情報＞
- https://news.mit.edu/2025/new-fuel-cell-could-enable-electric-aviation-0527
- https://www.cell.com/joule/fulltext/S2542-4351(25)00143-6
高エネルギー密度と低コストの電力を実現するナトリウム-空気燃料電池 Sodium-air fuel cell for high energy density and low-cost electric power
Karen Sugano ∙ Sunil Mair ∙ Saahir Ganti-Agrawal ∙ … ∙ Shashank Sripad ∙ Venkatasubramanian Viswanathan ∙ Yet-Ming Chiang
Joule Published:May 27, 2025
DOI:https://doi.org/10.1016/j.joule.2025.101962
Graphical abstract
Context & scale
Metals may be considered fuels in the same manner that hydrocarbons and hydrogen are fuels, since energy may be derived through combustion or electrochemical processes. Light metals such as lithium and sodium have particularly high specific energies that are attractive for hard-to-decarbonize transportation sectors, among others. Here, we show that sodium metal has merit as a low-cost, high energy density fuel by demonstrating a new kind of fuel cell operating on humidified air. Clean, high energy density electricity is produced while the discharge product of the fuel cell naturally captures atmospheric carbon dioxide, or it may be used as a valuable industrial chemical. Combined with historical precedents for the large volume production of sodium metal, this work suggests a pathway for utilization of sodium metal as a sustainable, low carbon energy carrier.
Highlights
•A liquid sodium-humidified air fuel cell using a solid electrolyte is demonstrated
•Stack-level energy density reaches 1,200 Wh/kg (1,295 Wh/L) at 80 mA/cm2
•Continuous operation consumes up to 2.3-cm-thick Na metal (2,500 mAh/cm2)
•The sodium hydroxide discharge product spontaneously captures atmospheric CO2
Summary
Alkali metal-air batteries have exceptional theoretical energy densities but suffer from poor rechargeability and low power largely due to the formation of solid discharge products. An alternative concept demonstrated here is a liquid sodium metal-air fuel cell incorporating a solid electrolyte membrane, wherein controlled humidification of the air stream continuously removes sodium hydroxide discharge product as a deliquesced liquid. This fuel cell reaches stack-level energy densities of 1,200 Wh/kg (1,295 Wh/L) at 80 mA/cm2 and 1,540 Wh/kg (1,760 Wh/L) at 40 mA/cm2 current density, while consuming up to 2.3-cm thickness of sodium metal (2,500 mAh/cm2 areal capacity) in continuous operation. The sodium hydroxide discharge product also readily captures ambient CO2. Combined with the high planetary abundance and low cost of sodium, the sodium-air fuel cell may be a more sustainable power source for hard-to-decarbonize transportation and stationary electrical power applications.
