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 degrees C. This work opens a newly promising avenue for advanced metal-CO2 batteries.