B-N co-doped biphenylene as a metal-free cathode catalyst for Li-O2 batteries: a computational study.

Lithium-oxygen batteries (LOBs) meet the growing demand for long-distance transportation over electric vehicles but face challenges because of the lack of high-performance cathode catalysts. Herein, using density functional theory calculations, we report a unique graphene allotrope, biphenylene, of which the doping structures exhibit great potential as metal-free catalysts for LOBs. Our modeling results demonstrate that the biphenylene nanosheets retain metallic properties after B doping, N doping, or B-N co-doping. Compared with the pristine biphenylene, the catalytic activity of the doped biphenylene is greatly improved due to charge redistributions. Notably, the overpotentials of the B-N co-doped biphenylene are as low as 0.19 and 0.18 V for the discharge and charge processes, respectively. Based on the electronic structure and bonding analysis, we identify two factors, i.e., Li-O bond strength and *Li2O2 adsorption energy, that can influence the Li-O2 electrochemical reactions. This study not only proposes a promising cathode catalyst but also provides insights into optimizing cathode catalysts for LOBs.