Lewis acidity controlled heme catalyst for lithium-oxygen battery

Abstract

Despite their high theoretical energy density, lithium-oxygen (Li−O2) batteries suffer from limited cyclability originating from poor charging efficiency. In an effort to overcome this critical issue, a variety of catalysts have been introduced, but much room still remains for further advancement in catalyst design. By benchmarking hemoglobin in red blood cells that carry oxygen at a well-defined center of the molecular cage, herein, we report heme as an air-cathode catalyst with iron (Fe) active sites. Furthermore, the coordination of electron-withdrawing ligands, such as thiocyanate (SCN) and azide (N3), to the Fe center enhances its Lewis acidity to weaken the binding of oxygen intermediates (O2∗) towards more facile decomposition of the main discharging product (Li2O2). Density functional theory calculations and surface energy analysis of Fe coherently support the advantageous role of the ligand engineering in enhancing the reversibility of a Li−O2 battery.