A battery that could store power for months at a time, while costing a fifth of today’s batteries, has been detailed in a new research paper. The breakthrough is thanks to a unique breathing-like mechanism that sends out oxygen to recharge and brings it in to discharge.

“This battery literally inhales and exhales air, but it doesn’t exhale carbon dioxide, like humans — it exhales oxygen,” says Yet-Ming Chiang, the Kyocera professor of materials science and engineering at MIT and co-author of a paper describing the battery. The research appeared on Wednesday in the journal Joule.

The system has wide-reaching implications for solar energy and other renewable sources. To avoid blackouts, large batteries store up energy when the source is generating electricity. Tesla’s project in South Australia, for example, will bring 129 megawatt-hours of storage to power 30,000 homes from renewables. Batteries like these cost at least around $100 per kilowatt-hour, but a system based on these new batteries would cost around $20 to $30.

“The intermittency for solar is daily, but for wind it’s longer-scale intermittency and not so predictable,” Chaing says. “When it’s not so predictable you need more reserve — the capability to discharge a battery over a longer period of time — because you don’t know when the wind is going to come back next.”

That’s where this battery comes in. The design allows it to discharge over a long period of time. Ions move between the electrodes as oxygen is taken in and out through a liquid salt solution. When oxygen flows into the cathode, the anode discharges to an external circuit. When oxygen flows out, the reverse happens and the battery is recharged.

The charging and discharging process in action.
The charging and discharging process in action.

Another aspect of the battery that could prove useful for large-scale projects is price. The team claim that the materials cost around 1/30th that of traditional lithium-ion batteries. It’s also much more compact in terms of energy density, opening it up to new uses.

“The energy density of a flow battery like this is more than 500 times higher than pumped hydroelectric storage,” Chiang says. “It’s also so much more compact, so that you can imagine putting it anywhere you have renewable generation.”

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