Theoretical investigation of a C2N monolayer as a bifunctional electrocatalyst for rechargeable non-aqueous Li–air batteries

Abstract

Lithium–air (Li–O₂) batteries have been the subject of extensive studies in the last few decades due to their high-energy density which is 5–10 times larger than those of conventional lithium-ion batteries. However, the sluggish reaction kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during discharging and charging processes, respectively, are the main problems that restrict the commercial application of Li–O₂ batteries. To overcome these challenges, we have designed the C₂N monolayer, a redox active carbon-based porous material, as a cathode catalyst for rechargeable non-aqueous Li–O₂ batteries. From the first principles calculations we have analyzed the stable adsorption configurations of *Li_xO_2y (x = 0–4, y = 0–2) intermediates on the C₂N monolayer and confirmed that the ORR during the discharging process follows a four-electron pathway with the formation of *Li₄O₂ as the discharge product. From the Gibbs free energy calculation, we have found that the overpotential values for ORR/OER during discharging/charging processes are only 0.36 V/0.64 V. In addition, the stability against non-aqueous solvent molecules (DMDMB and DMSO) and the side product Li₂CO₃ make the C₂N monolayer a potential cathode catalyst for non-aqueous Li–air batteries.