Engineering single-atom Mn on nitrogen-doped carbon to regulate lithium-peroxide reaction kinetics for rechargeable lithium-oxygen batteries

Abstract

Precision engineering of catalytic sites to guide more favorable pathways for Li2O2 nucleation and decomposition represents an enticing kinetic strategy for mitigating overpotential, enhancing discharge capacity, and improving recycling stability of Li-O2 batteries. In this work, we employ metal–organic frameworks (MOFs) derivation and ion substitution strategies to construct atomically dispersed Mn-N4 moieties on hierarchical porous nitrogen-doped carbon (Mn SAs-NC) with the aim of reducing the overpotential and improving the cycling stability of Li-O2 batteries. The porous structure provides more channels for mass transfer and exposes more highly active sites for electrocatalytic reactions, thus promoting the formation and decomposition of Li2O2. The Li-O2 batteries with Mn SAs-NC cathode achieve lower overpotential, higher specific capacity (14290 mA h g−1 at 100 mA g−1), and superior cycle stability (>100 cycles at 200 mA g−1) compared with the Mn NPs-NC and NC. Density functional theory (DFT) calculations reveal that the construction of Mn-N4 moiety tunes the charge distribution of the pyridinic N-rich vacancy and balances the affinity of the intermediates (LiO2 and Li2O2). The initial nucleation of Li2O2 on Mn SAs-NC favors the O2 → LiO2 → Li2O2 surface-adsorption pathway, which mitigates the overpotentials of the oxygen reduction (ORR) and oxygen evolution reaction (OER). As a result, Mn SAs-NC with Mn-N4 moiety effectively facilitates the Li2O2 nucleation and enables its reversible decomposition. This work establishes a methodology for constructing carbon-based electrocatalysts with high activity and selectivity for Li-O2 batteries.