Molecular Orbital Calculations on Stable Structures, Electronic and Lithiumabsorption Properties of BNB-substituted Graphite Sheets

Abstract

As a new carbon-based material for promising anode materials of rechargeable lithium ion batteries, BCN ceramics with a large amount of BNB units in a graphite-like sheet have been synthesized. In this study, we employed a polyaromatic hydrocarbon C96H24 as a model cluster for the graphite-like sheet and investigated the effect of BNB-unit substitutions on the electronic and Li-absorption properties of the sheet, by using a semiempirical molecular orbital method. The results are summarized as follows. (1) BNB substitutions prefer to occur at the periphery of C96H24 sheet, and the structures with more BN bonds are more stable. (2) By BNB substitutions, the surface of the potential energy for Li-absorption on the substituted sheets is largely changed to make the B-substituted sites more preferable for Li-absorptions. (3) Depending on the number of BNB-substitutions, the distribution of LUMO is remarkably changed, resulting in the change of Li-absorption sites. (4) Li absorption energies on the BNB-substituted sheets are larger than that on the B-substituted sheet.