First-principles study of catalytic mechanism of boron-doped graphene oxide on oxygen evolution reaction of lithium peroxide

Abstract

Lithium-oxygen batteries stand out among post-lithium-ion batteries due to their theoretically high energy density, while the sluggish reaction kinetics of lithium peroxide reduces the rate performance of the batteries. Therefore, improving the reaction kinetics of the lithium peroxide and then lowering the charge overpotential are of great importance for realizing reversible lithium-oxygen batteries with high energy density. In this work, the catalytic mechanism of graphene oxide (GO) and boron-doped graphene oxide (BGO) on the oxygen evolution reaction of (Li<sub>2</sub>O<sub>2</sub>)<sub>2</sub> cluster is investigated by first-principles calculations. The results show that the charge transfer from (Li<sub>2</sub>O<sub>2</sub>)<sub>2</sub> cluster to GO and from (Li<sub>2</sub>O<sub>2</sub>)<sub>2</sub> cluster to BGO are 0.59 e and 0.96 e, respectively, suggests that B doping improves the charge transfer from the discharged product to the cathode material. The Gibbs free energy of the 4-electron decomposition process shows that the (Li<sub>2</sub>O<sub>2</sub>)<sub>2</sub> cluster favors the Li-O<sub>2</sub>-Li decomposition pathway, and the rate-determining step for the reaction on both GO and BGO is the third step, that is, the removal of the third lithium. At the equilibrium potential, the charge overpotential of GO and BGO are 0.76 V and 0.23 V, respectively, showing that B doping greatly reduces the charging overpotential of lithium-oxygen batteries. Moreover, mechanistic analysis shows that B doping enhances the electronic conductance of GO and forms an electron-deficient active center, which facilitates charge transport in cathode and charge transfer from lithium peroxide to cathode materials, thereby reducing the charging overpotential of the lithium-oxygen batteries and improving its cycling performance. The B and O play a synergistic role in catalyzing the oxygen evolution reaction of (Li<sub>2</sub>O<sub>2</sub>)<sub>2</sub> clusters.