Boosted Mg-CO₂ Batteries by Amine-Mediated CO₂ Capture Chemistry and Mg²⁺ -Conducting Solid-electrolyte Interphases

Mg-CO₂ battery has been considered as an ideal system for energy conversion and CO₂ fixation. However, its practical application is significantly limited by the poor reversibility and sluggish kinetics of CO₂ cathode and Mg anode. Here, a new amine mediated chemistry strategy is proposed to realize a highly reversible and high-rate Mg-CO₂ battery in conventional electrolyte. Judiciously combined experimental characterization and theoretical computation unveiled that the introduced amine could simultaneously modify the reactant state of CO₂ and Mg²⁺ to accelerate CO₂ cathodic reactions on the thermodynamic-kinetic levels and facilitate the formation of Mg²⁺ -conductive solid-electrolyte interphase (SEI) to enable highly reversible Mg anode. As a result, the Mg-CO₂ battery exhibits boosted stable cyclability (70 cycles, more than 400 h at 200 mA g^-1 ) and high-rate capability (from 100 to 2000 mA g^-1 with 1.5 V overpotential) even at -15 °C. This work opens a newly promising avenue for advanced metal-CO₂ batteries.