High-Performance Li-CO2 Batteries Based on Metal-Free Carbon Quantum Dot/Holey Graphene Composite Catalysts

Li-CO2 batteries have attracted ever increasing attention due to their high energy and power densities. However, Li2CO3 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-CO2 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-CO2 battery, can support the fast formation and decomposition of Li2CO3 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-CO2 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.