Unveiling the electrocatalytic performance of h-AlN monolayer for nonaqueous Li-O2 batteries: a first-principles study.

Abstract

Although nonaqueous lithium-oxygen (Li-O2) batteries (LOBs) possess an exceptionally high theoretical energy density, their practical application is hindered by sluggish oxygen reduction/evolution reaction (ORR/OER) kinetics, large charge-discharge voltage gaps, and poor reversibility of insulating discharge products. Herein, density functional theory (DFT) calculations were performed to evaluate the h-AlN monolayer as a noble-metal-free bifunctional cathode electrocatalyst for LOBs. The h-AlN monolayer exhibits excellent structural stability, confirmed by formation energy, phonon spectrum, and ab initio molecular dynamics (AIMD) analyses. Initial adsorption analysis reveals that O2 adsorption is thermodynamically preferred over Li adsorption, indicating an O2-initiated discharge mechanism. Subsequent adsorption and reaction-energy analyses demonstrate that the ORR proceeds preferentially through a four-electron pathway, *O2 → *LiO2 → *Li2O2 → *Li3O2 → *Li4O2, with *Li4O2 identified as the preferred surface-bound terminal state along the modelled four-electron pathway. Adsorption of Li-O intermediates introduces electronic states near the Fermi level, narrows the band gap, and enhances interfacial charge transport. Within the modelled surface-pathway thermodynamic framework, Gibbs free-energy calculations yield low discharge and charge overpotentials of 0.178 and 0.104 V, respectively, resulting in a total overpotential of only 0.282 V. Furthermore, dimethyl sulfoxide (DMSO) adsorption and AIMD analyses indicate good electrolyte compatibility over the simulated timescale. Overall, these findings establish h-AlN as a promising bifunctional electrocatalyst for nonaqueous LOBs.

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