Researchers at the Department of Energy’s Oak Ridge National Laboratory are developing battery technologies to fight climate change in two ways, by expanding the use of renewable energy and capturing airborne carbon dioxide. 

This type of battery stores the renewable energy generated by solar panels or wind turbines. Utilizing this energy when wind and sunlight are unavailable requires an electrochemical reaction that, in ORNL’s new battery formulation, captures carbon dioxide from industrial emissions and converts it to value-added products.  

ORNL researchers recently created and tested two different formulations for batteries that convert carbon dioxide gas, or CO2, into a solid form that has the potential to be used in other products. 

One of these new battery types maintained its capacity for 600 hours of use and could store up to 10 hours of electricity. Researchers also identified, studied and overcame the primary challenge, a deactivation caused by chemical buildup, that had been an obstacle for the other battery formulation. 

“The Transformation Energy Science and Technology, or TEST, initiative at ORNL is precisely the kind of effort needed to address climate change. We are excited that ORNL is investing in innovative ideas and approaches that can transform the way we think about storing energy beyond lithium-ion batteries and other conventional electrochemical energy storage systems,” said Ilias Belharouak, an ORNL Corporate Fellow and initiative director. “What a fantastic scenario: Using free electrons to store CO2 and converting it to revenue-generating products is a concept I never would have imagined 10 years back, but this is just a start.” 

Batteries operate through electrochemical reactions that move ions between two electrodes through an electrolyte. Unlike cell phone or car batteries, those designed for grid energy storage do not have to function as a portable, closed system. This allowed ORNL researchers to create and test two types of batteries that could convert CO2 from stationary, industrial sources. 

For example, CO2 generated by a power plant could be pumped through a tube into the liquid electrolyte, creating bubbles similar to those in a carbonated soft drink. During battery operation, the gas bubbles turn into a solid powder. 

How it works

Each component of a battery can be made of different elements or compounds. These choices determine the battery’s operational lifetime, how much energy it can store, how big or heavy it is, and how fast it charges or consumes energy. Of the new ORNL battery formulations, one combines CO2 with sodium from saltwater using an inexpensive iron-nickel catalyst. The second combines the gas with aluminum. 

Each approach uses abundant materials and a liquid electrolyte in the form of saltwater, sometimes mixed with other chemicals. The batteries are safer than existing technology because their electrodes are stable in water, said lead researcher Ruhul Amin.

Very little CO2 battery research has been conducted. The previously-tried approach relies on a reversible metal-CO2 reaction that regenerates carbon dioxide, continuing to contribute greenhouse gases to the atmosphere. In addition, solid discharge products tend to clog the surface of the electrode, degrading the battery performance. 

However, the CO2 batteries developed at ORNL do not release carbon dioxide. Instead, the carbonate byproduct dissolves in the liquid electrolyte. The byproduct either continuously enriches the liquid to enhance battery performance, or it can be filtered from the bottom of the container without interrupting battery operation. Battery design can even be tuned to create more of these byproducts for use by the pharmaceutical or cement industries. The only gases released are oxygen and hydrogen, which do not contribute to climate change and can even be captured to produce energy or fuel.