Mo₂N–ZrO₂ Heterostructure Engineering in Freestanding Carbon Nanofibers for Upgrading Cycling Stability and Energy Efficiency of Li–CO₂ Batteries

Li–CO₂ batteries have attracted considerable attention for their advantages of CO₂ fixation and high energy density. However, the sluggish dynamics of CO₂ reduction/evolution reactions restrict the practical application of Li–CO₂ batteries. Herein, a dual-functional Mo₂N–ZrO₂ heterostructure engineering in conductive freestanding carbon nanofibers (Mo₂N–ZrO₂@NCNF) is reported. The integration of Mo₂N–ZrO₂ heterostructure in porous carbons provides the opportunity to simultaneously accelerate electron transport, boost CO₂ conversion, and stabilize intermediate discharge product Li₂C₂O₄. Benefiting from the synchronous advantages, the Mo₂N–ZrO₂@NCNF catalyst endows the Li–CO₂ 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–CO₂ batteries.