Researchers at MIT have made a new lithium-based battery that runs on carbon dioxide taken directly from a power plant. Their proof-of-concept battery, reported in the journal Joule, is a clever way to produce energy while cutting carbon dioxide emissions.
As the world continues to burn coal and natural gas for electricity, much research effort has been directed at ways to capture carbon dioxide from the smokestacks. The gas can be compressed and injected underground or in ocean beds. Researchers are also trying to turn the greenhouse gas into concrete, chemicals, fuels and other products.
The problem with carbon capture is that it is energy-intensive and expensive. The process uses chemicals such as amines to absorb carbon dioxide from exhaust gas. Then the amine has to be separated so that it can be reused and the carbon dioxide can be buried or processed further. All of this consumes energy. Power plants equipped with carbon capture systems generally use up to 30 percent of the electricity they generate just to power the capture, release, and storage of carbon dioxide.
The MIT researchers’ scheme involves using carbon dioxide as a component in a battery electrolyte. A battery is made of two electrodes and an electrolyte that shuttles lithium ions between them.
Others have tried making lithium-carbon dioxide batteries before. But making an electrolyte with carbon dioxide is difficult because the gas is not very reactive. So past work has involved adding expensive metal catalysts to the electrolyte.
Mechanical engineering professor Betar Gallant and her colleagues instead borrowed a page from the carbon capture processes. They added an amine to a lithium electrolyte so that it could capture carbon dioxide. They used this carbon dioxide-loaded electrolyte in a battery with a lithium anode and a carbon cathode.
As the device discharges, it converts carbon dioxide in the electrolyte into a solid carbonate. The reaction reverses during charging. But if the device were not being used as a rechargeable battery, it could be used as an efficient way to fix carbon dioxide into a solid form that can then be used for other things.
Lots more work needs to be done before the batteries can be practical, the researchers say. Right now, the devices can only be charged around 10 times; batteries in phones last for hundreds of recharge cycles. But the idea is promising. In the future, the system could operate continuously, generating power as a steady stream of carbon dioxide flows through it.
Source: Aliza Khurram, Mingfu He, and Betar Gallant. Tailoring the Discharge Reaction in Li-CO2 Batteries through Incorporation of CO2 Capture Chemistry. Joule, 2018.