Mo 2 N-ZrO 2 Heterostructure Engineering in Freestanding Carbon Nanofibers for Upgrading Cycling Stability and Energy Efficiency of Li-CO 2 Batteries.

Li-CO 2 batteries have attracted considerable attention for their advantages of CO 2 fixation and high energy density. However, the sluggish dynamics of CO 2 reduction/evolution reactions restrict the practical application of Li-CO 2 batteries. Herein, a dual-functional Mo 2 N-ZrO 2 heterostructure engineering in conductive freestanding carbon nanofibers (Mo 2 N-ZrO 2 @NCNF) is reported. The integration of Mo 2 N-ZrO 2 heterostructure in porous carbons provides the opportunity to simultaneously accelerate electron transport, boost CO 2 conversion, and stabilize intermediate discharge product Li 2 C 2 O 4 . Benefiting from the synchronous advantages, the Mo 2 N-ZrO 2 @NCNF catalyst endows the Li-CO 2 batteries with excellent cycle stability, good rate capability, and high energy efficiency even under high current densities. The designed cathodes exhibit an ultrahigh energy efficiency of 89.8% and a low charging voltage below 3.3 V with a potential gap of 0.32 V. Remarkably, stable operation over 400 cycles can be achieved even at high current densities of 50 µA cm -2 . This work provides valuable guidance for developing multifunctional heterostructured catalysts to upgrade longevity and energy efficiency of Li-CO 2 batteries.