Freestanding Mo 3 N 2 nanotubes for long‐term stabilized 2e − intermediate‐based high energy efficiency Li–CO 2 batteries

Abstract Li–CO 2 batteries are considered one of the promising power sources owing to ultrahigh energy density and carbon fixation. Nevertheless, the sluggish reaction kinetics of 4e − discharged process (Li 2 CO 3 ) impede its potential application. One of the efficient strategies for developing cathode catalysts is to stabilize 2e − intermediate Li 2 C 2 O 4 and improve reaction reversibility. However, long‐term catalysts of stabilized Li 2 C 2 O 4 are barely achieved, whereas cycle stability is far from satisfactory level. Herein, non‐noble metal–based Mo 3 N 2 is synthesized and employed as freestanding cathodes for Li–CO 2 batteries. Owing to rich delocalized electrons of Mo 2+ and reversible electron localization structure, freestanding Mo 3 N 2 cathodes exhibit a low charge potential (3.28 V) with an ultralow potential gap (0.64 V), high energy efficiency of up to 80.46%, fast rate capability, and outstanding cycle stability (>910 h). In situ experiments and theoretical calculation verify that Mo 3 N 2 stabilizes 2e − Li 2 C 2 O 4 intermediate by the interaction of Mo 2+ as active sites where Mo 2+ promotes the transfer of outer electrons to O, prevents its disproportionation to Li 2 CO 3 , and promotes reaction kinetics, contributing to high energy efficiency and outstanding cycle reversibility. In addition, the pouch‐cells deliver ultrahigh energy density of up to 6350.7 W h kg −1 based on the mass of cathode materials.