Boosted Reaction Kinetics of Li-CO₂ Batteries by Atomic Layer-Deposited Mo₂N on Hydrogen Substituted Graphdiyne

Li-CO2 batteries show promising prospects in both high energy density storage and efficient CO2 fixation. However, the sluggish kinetics of the decomposition of the CO2 reduction product Li2CO3 in the batteries cause high overpotentials and poor rechargeability. Herein, carbon/metal nitride composite catalysts composed of hydrogen-substituted graphdiyne (HsGDY) with atomic layer-deposited Mo2N are fabricated. The homogeneously atomically deposited Mo2N on the HsGDY substrate significantly accelerates the reaction kinetics of the CO2 reduction and Li2CO3 decomposition (CO2 evolution) processes in Li-CO2 batteries. The as-fabricated Li-CO2 batteries deliver an ultrahigh full discharge capacity of 37,416 mA hg(-1) and show a significantly decreased voltage gap of 1.13 V (with a median discharge/charge voltage of 2.82 V/3.95 V) at a current density of 0.1 Ag(-1). Furthermore, the battery also shows long-term stability of 1200 h (61 cycles) at 0.1 Ag(-1) with a cutoff capacity of 1000 mA hg(-1), outstanding rate capability and cyclability up to 2.0 Ag(-1), a well-maintained median discharge voltage of 2.67 V, and a charge voltage of 4.24 V. This work sheds light on designing and fabricating efficient and durable catalysts for high-performance Li-CO2 batteries.