MnTiO3 as a carbon-free cathode for rechargeable Li–O2 batteries

Abstract

Li–O₂ batteries (LOBs) are next-generation energy storage systems. However, their main challenges are the sluggish kinetics of oxygen reduction and evolution reactions (ORR/OER) and high charge overpotentials due to the formation of discharge product (Li₂O₂). To address this challenge, developing a catalyst with a unique structure and exceptional catalytic properties is crucial to enhancing the reversible cycling performance of LOBs, particularly under high current density conditions. Herein, the transition metal-based perovskite MnTiO₃ was examined as a carbon-free cathode catalyst using density functional theory (DFT) calculations and experimental techniques. The intrinsic advantages of MnTiO₃ stem from the coexistence of Mn and Ti energy levels near the Fermi level, as revealed by our density of states (DOS) analysis. This electronic structure facilitates ORR/OER, thus endowing MnTiO₃ with a bifunctional role in promoting battery performance. Our DFT-based investigation elucidates the surface stability and catalytic properties of MnTiO₃. Furthermore, Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) confirm that the electrochemical reaction on MnTiO₃ follows a two-electron pathway. Our findings reveal that a LOB with MnTiO₃ exhibits a total overpotential of 1.18 V and 1.55 V using DFT and electrochemical measurements, respectively. High current densities up to 1 A g⁻¹ also highlight its potential as a cathode catalyst for LOBs.