Researchers have developed a more efficient, more reliable potassium-oxygen battery with a cathode that stores the energy produced by a chemical reaction in a metal-oxygen or metal-air battery. The battery could make renewable energy sources like solar and wind more viable options for the power grid through cheaper, more efficient energy storage.
Renewable energy sources don't emit carbon dioxide, so they don't contribute to global warming but they provide energy only when the Sun is shining or the wind is blowing. In order for them to be reliable sources of power for a region's energy grid, there must be a way to store excess energy gathered from sunshine and wind. The improved potassium-oxygen batteries could be more efficient than lithium-oxygen batteries while simultaneously storing about twice the energy as existing lithium-ion batteries.
Previously, potassium-oxygen batteries degraded with each charge, never lasting longer than five or 10 charging cycles — far from enough to make the battery a cost-effective solution for storing power. That degradation happened because oxygen crept into the battery's anode — the place that allows electrons to charge a device, be it a cellphone or a power grid. The oxygen caused the anode to break down, so the battery itself could no longer supply a charge.
The new design works a bit like human lungs: Air comes into the battery through a fibrous carbon layer, then meets a second layer that is slightly less porous, and finally ends at a third layer that is barely porous at all. That third layer, made of the conducting polymer, allows potassium ions to travel throughout the cathode but restricts molecular oxygen from getting to the anode. The design means that the battery can be charged at least 125 times, giving potassium-oxygen batteries more than 12 times the longevity they previously had with low-cost electrolytes.
Oxygen batteries have higher energy density, which means they can improve the range of electric vehicles and battery life of portable electronics, for example, though other challenges must be overcome before potassium-oxygen batteries are viable for these applications.