<p>➀ MIT researchers developed a sodium-air fuel cell with 3x higher energy density than lithium-ion batteries, potentially enabling electric aviation; </p><p>➁ The system uses liquid sodium and air, produces sodium bicarbonate as a carbon-capturing byproduct, and addresses safety through separated reactants; </p><p>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.</p>