Dissociation of (Li2O2)0,+ on graphene and boron-doped graphene: insights from first-principles calculations

Abstract

Reducing charge overpotential is of great significance to enhance the efficiency and cyclability of Li–O₂ batteries. Here, a dramatically reduced charge overpotential via boron-doped graphene as a catalytic substrate is successfully predicted. By first-principles calculations, from the perspective of reaction thermodynamics and kinetics, the results show that the electrochemical oxidation of the Li₂O₂⁺ cation is easier than the chemical oxidation of the neutral Li₂O₂ molecule, and the oxidation of (Li₂O₂)^0,+ is facilitated by boron-doping in pristine graphene. More importantly, the results reveal the oxidation mechanism of (Li₂O₂)^0,+: two-step dissociation with the LiO₂ molecule as a reactive intermediate has advantages over one-step dissociation; the rate-determining step for the dissociation of (Li₂O₂⁺)_G is the oxygen evolution process, while the lithium removal process is the rate-determining step for the dissociation of (Li₂O₂⁰)_G, (Li₂O₂⁰)_BG, and (Li₂O₂⁺)_BG.