NiMn-based metal-organic framework with optimized eg orbital occupancy as efficient bifunctional electrocatalyst for lithium-oxygen batteries

Abstract

Rational design and synthesis of highly efficient bifunctional oxygen electrocatalysts is significant for rechargeable lithium-oxygen batteries (LOBs). In this work, a bimetal coupling strategy has been adopted to fabricate Ni/Mn bimetal-organic framework (Ni/Mn-MOF). The LOBs equipped with NiMn0.05-MOF electrocatalyst exhibit excellent performances with large specific capacity of 28,464 mAh/g and extraordinary stability of 524 cycles at 100 mA g−1. Combining with the experimental results and density functional theory (DFT) calculation, it is found that the doped Mn cations enable triggering the redistribution of 3d electron in Ni sites, adjusting eg orbital occupancy of Ni and strengthening the hybridization between Ni −3d and O −2p orbits due to the intense electron coupling between Ni and Mn ions, which greatly optimizes the inherent absorption capability of NiMn0.05-MOF for LiO2 intermediate and thus decreases the energy barriers of oxygen redox reactions.