CO2/oxalate cathodes as safe and efficient alternatives in high energy density metal–air type rechargeable batteries

Abstract

We present theoretical analysis on why and how rechargeable metal–air type batteries can be made significantly safer and more practical by utilizing CO₂/oxalate conversions instead of O₂/peroxide or O₂/hydroxide ones, in the positive electrode. Metal–air batteries, such as the Li–air one, may have very large energy densities, comparable to that of gasoline, theoretically allowing for long range all-electric vehicles. There are, however, still significant challenges, especially related to the safety of their underlying chemistries, the robustness of their recharging and the need of supplying high purity O₂ from air to the battery. We point out that the CO₂/oxalate reversible electrochemical conversion is a viable alternative of the O₂-based ones, allowing for similarly high energy density and almost identical voltage, while being much safer through the elimination of aggressive oxidant peroxides and the use of thermally stable, non-oxidative and environmentally benign oxalates instead.