Renewable energy might be clean, but it’s not always reliable if the Sun ducks behind clouds or the wind slacks off. To counter that variability, the grid will need to combine a range of different sources, such as solar, wind, hydro, waves, and biomass, with large-scale energy storage systems. Now, an MIT team has developed a new type of battery that could fit the bill. It breathes air, and can store energy long-term for about a fifth of the cost of existing technologies.
The new design is a rechargeable flow battery, meaning its cathode and anode components are liquids (catholyte and anolyte) that pass ions back and forth to store or release energy. In this case, the anolyte is made up of sulfur dissolved in water, and the hunt for an equally abundant material for the catholyte led the team to an oxygenated liquid salt solution.
“We went on a search for a positive electrode that would also have exceptionally low cost that we could use with sulfur as the negative electrode,” says Yet-Ming Chiang, co-author of the study. “Through an accidental laboratory discovery, we figured out that it could actually be oxygen, and therefore air. We needed to add one other component, which was a charge carrier to go back and forth between the sulfur and air electrode, and that turned out to be sodium.”
The clever part of the battery is the fact that the catholyte “breathes” in air in from outside while discharging, and exhales while recharging. By this mechanism, the battery creates negatively-charged hydroxide ions in the catholyte while inhaling, and while recharging that oxygen is released, creating hydrogen ions which then send electrons back into the anolyte.
“This battery literally inhales and exhales air, but it doesn’t exhale carbon dioxide, like humans — it exhales oxygen,” says Chiang. “What this does is create a charge balance by taking oxygen in and out of the system.”
Recent Comments