A New Approach to Carbon Dioxide Utilization: The Carbon Molten Air Battery
Authors: Licht Stuart , Johnson Marcus , Lefler Matthew J. , Vicini Juan 
Published: February 2020

As the levels of carbon dioxide (CO2) increase in the Earth’s atmosphere, the effects on climate change become increasingly apparent. With the demand to reduce our dependence on fossils fuels and lower our carbon emissions, a transition to renewable energy sources is necessary. Cost effective large-scale electrical energy storage must be established for renewable energy to become a sustainable option for the future. We've previously shown that carbon dioxide can be captured directly from the air at solar efficiencies as high as 50%, and that carbon dioxide associated with cement formation and the production of other commodities, such as ammonia and iron, can be electrochemically avoided in the STEP process.1-6

The carbon molten air battery, presented by our group in late 2013,7 as one of a new class of rechargeable “molten air” batteries that utilize a molten electrolyte and a quasi-reversible air electrode,7-10 is attractive due to its scalability, location flexibility, and construction from readily available resources, providing a battery that can be useful for large scale applications, such as the storage of renewable electricity.
Uncommonly, the carbon molten air battery can utilize carbon dioxide directly from the air:7,11-18

charging: CO2(g) → C(solid) + O2(g) (1)
discharging: C(solid) + O2(g) → CO2(g) (2)
More specifically, in a molten carbonate electrolyte containing added oxide, such as lithium carbonate with lithium oxide, the 4 electron charging reaction eq. 1 approaches 100% faradic efficiency and can be described as the following two equations:
O2-
(dissolved) + CO2(g) → CO3
2-
(molten)
(1a)
CO3
2-
(molten) → C(solid) + O2(g) + O2-
(dissolved)
(1b)
Using carbon formed directly from the CO2in our earth’s atmosphere, the carbon molten air battery is a viable system to provide large-scale energy storage.

References

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Figure: Variations of the Molten Battery.

Figure 1