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. (C) 2002 Elsevier Science Ltd. All rights reserved.