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.