High‐Performance Li‐CO 2 Batteries Based on Metal‐Free Carbon Quantum Dot/Holey Graphene Composite Catalysts

Li‐CO 2 batteries have attracted ever increasing attention due to their high energy and power densities. However, Li 2 CO 3 formed during the discharge process is difficult to decompose, leading to a large charge overpotential and poor cyclability. Thus, high‐performance and low‐cost catalysts that can be integrated into the electrode architecture are urgently needed for the development of practical Li‐CO 2 batteries with a low overpotential and long cyclability. Herein, a high‐performance composite catalyst is reported based on carbon quantum dots supported by holey graphene (CQD/hG), which, when used as the cathodic catalyst in a Li‐CO 2 battery, can support the fast formation and decomposition of Li 2 CO 3 in organic electrolytes and achieve an overpotential as low as 1.02 V (Li/Li + ) at current density of 0.1 A g −1 . The discharge capacity of this Li‐CO 2 battery is 12300 mAh g −1 under the current density of 0.5 A g −1 , showing an excellent long‐term stability with up to 235 cycles even at a high current density of 1 A g −1 . The observed superb battery performance is attributable to synergistic effects that the CQD/hG composite architecture provides a high catalytic activity of the defect‐rich CQDs and fast electron/electrolyte transport through the conducting holey graphene sheets.