Systematic theoretical study of Li adsorption on stable BN- and B-substituted aromatic hydrocarbons

The interaction of Li atoms with BN- and B-substituted hydrocarbons was examined. A substantial number of prescreened stable BN- and B-isomers of anthracene and phenanthrene at all possible degrees of doping were used as models for adsorption of a Li-atom. The energy of the Li/substrate systems was calculated with the UMP2/6-31G∗ method. The total and the binding energies (BSSE and ZPE corrected) at each adsorption position of Li over the substituted hydrocarbons were evaluated. On the basis of the energy estimates and analysis of the molecular orbitals and electron density distribution, factors governing the preferred locations of the Li-atom on BN- and B-substituted anthracenes and phenanthrenes with different degrees of doping were outlined. Li positioned closer and bonded tighter to the substituted than to the pristine hydrocarbons. Optimal parameters ensuring minimum irreversible capacity of the substrate were defined: medium binding of Li combined with maximum charge transfer - requirements met by BN-anthracenes and B-phenanthrenes at low degree of doping and B-anthracenes with higher B-contents, the two latter being more prospective. The results provide valuable information for the molecular design of anode materials for Li-ion batteries with improved performance.