A team of researchers at MIT, led by Professor Yet-Ming Chiang, has developed a groundbreaking sodium-air fuel cell that could potentially revolutionize energy storage in sectors where the replacement of fossil fuels is challenging. The fuel cell, designed to run on liquid sodium, offers a higher energy density compared to lithium-ion batteries and eliminates the need for the extreme conditions required by hydrogen fuel cells, making it a more practical solution for transportation modes like regional aviation and short-distance shipping. The sodium-metal-based system demonstrated an impressive energy density of around 1,200 watt-hours per kilogram, far exceeding the capabilities of current commercial lithium-ion batteries. By operating at moderate temperatures and utilizing liquid sodium, the fuel cell showcases promising potential for applications in various modes of transport. Safety concerns associated with the reactivity of sodium metal are addressed through the design of the cell, which ensures the continuous removal of water produced during reactions to prevent harmful interactions. Additionally, the incorporation of a solid electrolyte material further enhances the safety features of the technology. Economically, sodium-based systems present advantages due to the potential for scaling up production of sodium metal from inexpensive sources like sodium chloride. With a historical precedent of sodium metal production and the possibility of leveraging existing supply chains, the commercial viability of sodium-based fuel cell systems appears promising. The research, published in Joule, has garnered positive attention from experts in the field for its innovative approach to energy storage. The project has received funding from ARPA-E's Propel-1K program and has led to the establishment of a company, Propel Aero, aimed at commercializing the technology. Future steps involve further research to enhance performance and energy density, as well as the development of small-scale systems to demonstrate the practical applications of sodium-metal fuel cells.