Binder-free MoN nanofibers catalysts for flexible 2-electron oxalate-based Li-CO${}_2$ batteries with high energy efficiency

Owing to the ultrahigh theoretical energy density and environmental friendliness of CO${}_2$ fixation, Li-CO${}_2$ batteries are regarded as one of sustainable high-energy-density power sources for different applications including wearable electronics. Most of reported Li-CO${}_2$ batteries utilize expensive, noble metal-based catalysts via 4-electron Li${}_2$CO${}_3$ as discharged products, leading to low energy efficiency, electrolyte side-reaction, and sluggish reaction kinetics. Herein, a 2-electron Li-CO${}_2$ battery based on noble metal-free and binder-free MoN nanofibers on carbon cloth is fabricated with high energy efficiency and fast reaction kinetics. The fabricated batteries exhibit an initial median charge potential of low to 3.19 V with a potential gap of 0.36 V, high energy efficiency up to 88%, and >500 h cycle stability. Experimental and theoretical computation results demonstrate that Li${}_2$C${}_2$O${}_4$ as 2-electron intermediate products are stabilized by delocalized electrons of Mo${}^{3+}$ in MoN to form the Mo-O coupling bridge, leading to reversible Li${}_2$C${}_2$O${}_4$ formation/decomposition accompanied with high energy efficiency and fast battery reaction. The batteries also show superior flexibility and stable power output under different deformations. (© 2022 Wiley‐VCH GmbH)