➀ MIT researchers developed a sodium-air fuel cell with 3x higher energy density than lithium-ion batteries, potentially enabling electric aviation;

➁ The system uses liquid sodium and air, produces sodium bicarbonate as a carbon-capturing byproduct, and addresses safety through separated reactants;

➂ Startup Propel Aero aims to commercialize the technology for regional flights and drones, with a 1,000 Wh/kg prototype targeted within a year.