Oxygen Redox Kinetics Regulation by Intermediate-Enriched Electrochemical Interfaces in Li-O2 Batteries.

Abstract

Li-O2 batteries with high theoretical energy density are limited by low kinetics due to the insulating discharge product, which passivates the cathode surface, and hindering oxygen reduction/evolution reactions (ORR/OER). Herein, methylamine-intercalated MoS2 (MIMS) nanoflowers were synthesized and applied as the cathode to promote the catalytic reactions of Li-O2 batteries. The introduction of electron-rich methylamine facilitates charge injection into Mo 4d orbitals of MoS2, triggering its phase transition from 2H to 1T. This results in an elevated d-band center to enhance the adsorption energies toward key intermediate LiO2, boosting formation of film-like Li2O2. In situ EIS data combined with distribution of relaxation times (DRT) and distribution of capacitive times (DCT) analyses reveal the distinct electrocatalytic mechanisms of MIMS and MS cathodes, effectively illustrating the enhanced capacitive contribution and reduced interfacial impedance induced by dynamic oxygen intermediate evolution at the electrochemical interfaces on MIMS cathodes. The resultant Li-O2 batteries show a reduced voltage gap (0.85 V), high discharge/charge capacities (19083/18839 mAh g-1), and long-term stability (620 cycles at 1000 mA g-1). Besides, the fabricated pouch cells deliver a high energy density of 726.7 Wh kg-1 and stable operation over 1000 h, showing promise for practical use. These findings demonstrate the contribution of intercalation to the regulation of the interfacial chemistry and electrochemical performance of Li-O2 batteries.