Reversible Carbon Dioxide/Lithium Oxalate Regulation toward Advanced Aprotic Lithium Carbon Dioxide Battery

Li-CO₂ batteries have received significant attention owing to their advantages of combining greenhouse gas utilization and energy storage. However, the high kinetic barrier between gaseous CO₂ and the Li₂CO₃ product leads to a low operating voltage (<2.5 V) and poor energy efficiency. In addition, the reversibility of Li₂CO₃ has always been questioned owing to the introduction of more decomposition paths caused by its higher charging plateau. Here, a novel "trinity" Li-CO₂ battery system was developed by synergizing CO₂, soluble redox mediator (2,2,6,6-tetramethylpiperidoxyl, as TEM RM), and reduced graphene oxide electrode to enable selective conversion of CO₂ to Li₂C₂O₄. The designed Li-CO₂ battery exhibited an output plateau reaching up to 2.97 V, higher than the equilibrium potential of 2.80 V for Li₂CO₃, and an ultrahigh round-trip efficiency of 97.1 %. The superior performance of Li-CO₂ batteries is attributed to the TEM RM-mediated preferential growth mechanism of Li₂C₂O₄, which enhances the reaction kinetics and rechargeability. Such a unique design enables batteries to cope with sudden CO₂-deficient environments, which provides an avenue for the rationally design of CO₂ conversion reactions and a feasible guide for next-generation Li-CO₂ batteries.