Rechargeable Li‐CO ₂ Batteries Enabled by a Bifunctional Imidazolium Ionic Liquid Electrolyte

ABSTRACT The practical operation of Li‐CO 2 batteries is severely limited by sluggish CO 2 redox kinetics and the irreversible accumulation of crystalline Li 2 CO 3 during discharge/charge processes. To address these challenges, we developed a bifunctional imidazolium‐based ionic liquid, [ACNMIm][TFSI], featuring a cation functionalized with ‐NH 2 and ‐C≡N groups, which serve as dual active sites for stabilizing reaction intermediates and chemical CO 2 capture. The Li‐CO 2 batteries with 30% vol [ACNMIm][TFSI] electrolytes deliver an exceptional discharge capacity of up to 29678 mAh g −1 at 100 mA g −1 and maintain stable cycling performance for over 1000 h under a fixed capacity limit of 1000 mAh g −1 . Mechanistic studies confirm that the TFSI − anions participate in reorganizing the Li + solvation shell through competitive coordination, effectively suppressing solvent oxidation and improving interfacial stability. Furthermore, the ‐NH 2 and ‐C≡N functional groups on the [ACNMIm] + cation tailor the electronic structure, which optimizes the local electrolyte microenvironment and facilitates the formation of amorphous/low‐crystallinity Li 2 CO 3 phases, a feature that is highly favorable for the reversible decomposition of such discharge products. This work establishes a functional cation design principle for ionic liquid electrolytes, linking molecular level coordination and CO 2 ‐philic sites to reversible carbonate formation/decomposition for Li‐CO 2 batteries.