Freestanding Mo₃N₂ nanotubes for long‐term stabilized 2e⁻ intermediate‐based high energy efficiency Li–CO₂ 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, longterm 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. K E Y W O R D Scarbon-free, freestanding, high energy efficiency, Li-CO 2 batteries, Mo 3 N 2 nanotubes 1This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Determinants of the Surface Film during the Discharging Process in Lithium–Oxygen Batteries

“…Aprotic lithium–oxygen (Li–O 2 ) batteries based on the formation and decomposition of lithium peroxide (Li 2 O 2 ) have one of the highest specific energies of 3500 Wh kg –1 , attracting worldwide research interest. − However, many challenges remain before commercialization, and one of them is early cell death, where the practical specific capacity and specific energy are much lower than the theoretical values. − During discharge, oxygen is reduced to form solid lithium peroxide (Li 2 O 2 ), which would further react to form undesired byproducts, such as lithium carbonate, both accumulating within the porous electrode. The pore clogging, the surface passivation of desired insulating Li 2 O 2 products, and the formation of undesired byproducts all contribute to premature cell death, which is all dependent upon the formation of the discharge product Li 2 O 2 . ,− …”

Tailoring Li–CO2 Electrochemistry Based on 4,4′-Bipyridine Redox Cycle

“…The most common one involves CO 2 being reduced and released via a four-electron pathway, i.e., 4Li + + 3CO 2 + 4e – ↔ 2Li 2 CO 3 + C. , The other two are two-electron pathways, i.e., 2Li + + 2CO 2 + 2e – ↔ CO + Li 2 CO 3 , and 2Li + + 2CO 2 + 2e – ↔ Li 2 C 2 O 4 . , Over the past few years, many endeavors have been made to develop working strategies to regulate the reaction kinetics and boost electrochemical performance of Li–CO 2 batteries . For instance, solid electrocatalysts, including carbon materials, , metals, ,, metal oxides, − metal–organic frameworks, , metal nitrided, etc., have been observed to reduce the discharge/charging overpotential to some extent, but they are susceptible to failure when their surface is covered with solid discharge product. Moreover, some solid electrocatalysts can easily induce irreversible electrolyte decomposition particularly during charge of the Li–CO 2 batteries .…”