Interaction of hydrogen-edged boron nitride flakes with lithium: boron nitride as a protecting layer for a lithium-ion battery and a spin-dependent photon emission device

Abstract

In this study, the electronic properties of pristine and Li-doped BN flakes have been studied by first-principle density functional theory and the B3LYP/6-31G(d,p) level. Accordingly, for pristine flakes, stability increases as the size increases. For doped flakes, the adsorption energy also increases as the size increases. And, for the N − H bond adsorption, we have the maximum stability. The distance of the adsorbed Li atom from the BN surface decreases as the adsorption place becomes farther from the symmetry point of the BN flake. For pristine BN the bond lengths do not change as the size increases, and the changes of the bond lengths of doped BN is in order of 0.01 Å. About the gap, for pristine BN, the gap increases as the size decreases. Furthermore, for doped structures, a little spin is transferred to the doped BN layer and some states are spin-polarized. A large value of the HOMO-LUMO gap for pristine and spin-down current leads to this point that we have a wide gap insulator for pristine BN and spin-down states. While, for spin-up electrons, the gap amounts are between 2 and 2.9 eV posses that we have a semiconductor. Additionally, in doped cases, by the increase of the α gap, the β gap of the spin-up states decreases. Frontier molecular orbitals have also been studied to discuss the ground and excited states. The trends seen in the DOS spectrum and charge distribution are also observed in the present work for pristine and Li-doped BNs. Moreover, the doped BNs posses non-zero dipole moments due to the asymmetry in the charge distribution. Finally, we have suggested an application for the BN as a protecting layer for a Lithium-ion battery. Besides, its photoluminescence properties for optoelectronic applications have been discussed.