Low Overpotential of Long Cycle Non-aqueous Mg-CO₂ Batteries

Magnesium carbon dioxide (Mg-CO₂) batteries, in which use greenhouse gas carbon dioxide was used as the positive electrode active material, have the advantages of efficient energy storage and value-added utilization of carbon dioxide, making them an attractive candidate for a new generation of battery. However, compared with other metal carbon dioxide battery systems, Mg-CO₂ batteries have received little attention so far, due to several severe issues, including relatively slow redox reaction kinetics in non aqueous environments, large decomposition energy barriers of discharge products and poor reversibility of multi electron three-phase positive electrode reactions. In order to solve these problems, molybdenum carbide carbon nanotubes (Mo₂C-CNTs) were used as positive electrode catalysts, and the discharge product was changed from the difficult to decompose magnesium carbonate (MgCO₃) to magnesium oxalate (MgC₂O₄), resulting in an extremely low overpotential (0.25 V) for the Mg-CO₂ battery, increased energy efficiency, and a working time of up to 2300 hours.. This work lays the foundation for the research of rechargeable non-aqueous Mg-CO₂ batteries that can simultaneously address energy and environmental issues.