Metallic Penta-BN2 monolayer: A novel platform for non-lithium-ion batteries with high capacity and splendid cyclicity

Investigating high-capacity anode materials for non-lithium-ion batteries (NLIBs) would further enhance the possibility of the human being free from fossil energy. By applying the first-principles calculation method based on density functional theory, in this work, the scientific feasibility of employing penta-BN2 monolayer as anode material for NLIBs (Na, K, Mg, and Ca-ion batteries) is systematically investigated. The results show that the penta-BN2 exhibits excellent thermodynamic stability and superior electrical conductivity, and its intrinsic metallic property is maintained after ionization. Remarkably, the calculated theoretical specific capacities of penta-BN2 monolayer are 690.23, 690.23, 1380.45, and 1380.45 mAh.g(-1) for Na+, K+, Mg2+, and Ca2+, respectively, which are outstanding among most of the previously proposed candidate anode materials for NLIBs. In addition, the moderate open-circuit voltages of penta-BN2 make itself suitable for anode applications. More importantly, the splendid reversibility of penta-BN2 contributes to extremely low diffusion energy barriers for metal ions. These results suggest that the penta-BN2 monolayer has a promising application prospect as anode for NLIBs with high energy density and outstanding rate performance.