Molecular orbital calculations on electronic and Li-adsorption properties of sulfur-, phosphorus- and silicon-substituted disordered carbons

To clarify the effect of atom substitution on electronic and lithium (Li) adsorption properties of disordered carbons, we employed circum-coronene (C₅₄H₁₈) as a model cluster for disordered carbons and investigated the stable structures, electronic and Li-adsorption properties of its sulfur-, phosphorus- and silicon-substituted sheets, by using a semiempirical molecular orbital method. Among the three substituted sheets, the silicon-substituted Si₂C₅₂H₁₈ sheet was found to have desirable properties as an anode material of rechargeable Li-ion batteries: planar structure and large amount of Li adsorption. Although the Li-adsorption energy of Si₂C₅₂H₁₈ is smaller than that of B₂C₅₂H₁₈, the dependence of adsorption energy on the number of Li atoms indicates that Si₂C₅₂H₁₈ can adsorb more Li atoms than B₂C₅₂H₁₈. Therefore, silicon- as well as boron-substituted disordered carbons are expected to be promising materials for the anode in Li-ion batteries.