Enhancing redox stability of lithium–oxygen batteries via introducing an oxygen pre-coordinated vanadyl phthalocyanine catalyst

Abstract

Since various metal phthalocyanines (MPcs) possesses the properties of transferring electrons and spontaneously binding with oxygen species, their application as catalysts in Li–O₂ batteries (LOBs) can stabilize the highly active superoxide radical (O²⁻) to suppress side reactions, leading to enhanced electrochemical performance. MPcs have usually considered common binding behavior directly with empty metal center. However, no attempt has been made to employ MPcs with pre-coordination of the oxygen group on the metal center, which can result in unexpected catalytic behavior. In this work, we demonstrate that a novel oxygen-pre-coordinated MPc catalyst, vanadyl phthalocyanine (VOPc), can facilitate the formation and decomposition of Li-containing discharge products, such as Li_xO₂, during charging/discharging in LOBs. This results in enhanced electrochemical performance, including decreased polarization and stable cycling-performance. Moreover, redox mediation and reaction pathways in the oxygen-pre-coordinated VOPc-applied LOB are confirmed through combined studies using first-principles calculations and various experiments, clearly supporting that the effective catalytic effect of oxygen-pre-coordinated VOPc affords the outstanding electrochemical properties of the LOB.