One of the challenges in totally decarbonizing our economy is that solar and wind energy is variable. Wind farms produce electricity when it’s breezy; solar panels generate energy during the day, but most electricity generation relies on coal and natural gas as backup when the wind isn’t blowing and the sun isn’t shining. Because lithium-ion batteries are too expensive to solve these problems, the recent unveiling of an aqueous air battery system that uses safe, cheap and abundant materials is a huge breakthrough.