First-Principles Study of the Lithium Interaction with Polycyclic Aromatic Hydrocarbons

Abstract

We have performed first-principles calculations in order to understand the binding mechanism of Li atoms in disordered carbon materials that are used for negative electrodes of rechargeable lithium batteries. We used pyrene, anthracene, and phenanthrene molecules as parts of disordered carbon. We examined several binding sites for two Li atoms in these aromatics and found that they are bound with substantial negative binding energies. The most negative one was -142.8 kJ/mol for Li-containing pyrenes, -211.0 kJ/mol for anthracenes, and -146.2 kJ/mol for phenanthrenes at the B3LYP/6-31G*//HF/6-31G* level of calculation. Li atoms are bound to interstitial (ring-over) and edge sites. In addition to these binding mechanisms, we found that Li atoms could be bound, forming a Li dimer in anthracene and phenanthrene. Their binding energies are -200.5 and -146.2 kJ/mol, respectively, being larger in magnitude than Li 2 dissociation energy. These aromatics lose their planarity when they accommodate Li atoms. We found that larger distortion brings more strong interaction between the aromatics and Li atoms. The amount of energy required for the distortion increases in the order the interstitial, edge, and Li-dimerized sites. The highest occupied molecular orbital energy, which is closely related to the electrode potential during discharge process, decreases in that order. This energy lowering may be related to the origin of the hysteresis observed during the charge/discharge cycles.

Quantum chemical modeling of infrared and Raman activities in lithium-doped amorphous carbon nanostructures: hexa-peri-hexabenzocoronene as a model for hydrogen-rich carbon materials

“…The most sophisticate calculations were carried out recently on relatively small aromatic hydrocarbons [3]. In this work we investigate the comparably larger HBC using the hybrid B3LYP functional [9] with the 6-31G Ã basis set.…”

“…In this work we investigate the comparably larger HBC using the hybrid B3LYP functional [9] with the 6-31G Ã basis set. This method was shown to provide results comparable with M€ oller Plesset perturbation theory to second order (MP2) calculations [3]. We considered the interaction of two lithium atoms with the PAH and explored more than 20 combinations of interaction sites corresponding to configurations with both lithium atoms on the same side of the PAH or with the two lithium atoms on opposite sides of the PAH surface.…”

“…A strong indication of local and specific interactions comes from the hysteresis observed during charge/discharge cycles in lithium batteries [3]. The hysteresis, along with the specific capacity of the lithium batteries, are somewhat related to the amount of hydrogen in the carbon sample used as negative electrode: an indication that the sites for lithium interaction in the proximity of hydrogen atoms behave differently from those away from hydrogen atoms.…”

Graphene/Li-ion battery

“…The tight binding calculations showed that a flat band, composed of side edge carbon atoms, is located near the Fermi level [33]. Ab initio calculations for the interaction of the lithium atom with graphite model clusters indicated that charge transfer from the Li atom to the graphite cluster is important in large-cluster size [34][35][36][37]. But properties of Nano-scrolls and edge effects on graphene need wider studies [14].…”

High-resolution electron spectroscopy, preferential metal-binding sites, and thermochemistry of lithium complexes of polycyclic aromatic hydrocarbons

“…[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] For Li-PAH neutral complexes, semiempirical computer simulations by Papanek et al showed that the high capacity of Li uptake by PAH molecules (Li atomic percent with respect to the number of carbon atoms) is partially attributable to Li binding at the hydrogen-terminated edges of pyrene, coronene, and several other PAH molecules, with local geometries analogous to the stable isomer of the organolithium molecule C 2 H 2 Li 2 . Interactions between Li/Li + and PAH molecules have been studied by many computational calculations.…”