Polycyclic Aromatic Hydrocarbons as Anode Materials in Lithium-Ion Batteries: A DFT Study

Area of Science:

• Computational Chemistry
• Materials Science
• Electrochemistry

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are crucial in various chemical and physical processes.
• Understanding the interaction of lithium species with PAHs is vital for energy storage applications.
• Density Functional Theory (DFT) provides a robust framework for studying molecular interactions and energetics.

Purpose of the Study:

• To investigate the structural and energetic aspects of Li+ and Li interactions with PAHs.
• To analyze the electron distribution and identify key interaction sites within PAHs.
• To predict the suitability of specific PAH derivatives as anode materials for lithium-ion batteries (LIBs).

Main Methods:

• Employed DFT calculations at the wB97XD/6-311G(d,p) level for structural and energetic analysis.
• Utilized Molecular Electrostatic Potential (MESP) topology to categorize PAH aromatic rings and analyze electron distribution.
• Calculated adsorption energies (E1, E2) and dissociation energy (E3) for Li+/Li-PAH complexes.

Main Results:

• Categorized PAH rings into five types (Rs, Rn, Rd, Rb, Re), with sextet-type (Rs) and naphthalene-type (Rn) showing highest Li+ interaction.
• Found a proportionality between the change in MESP at Li+ nucleus (ΔVLi+) and adsorption energy (E1) for Li+...PAH complexes.
• Observed Li+...PAH•- formation in Li-PAH interactions due to electron transfer; dissociation energy (E3) correlated well with MESP data (ΔVLi).

Conclusions:

• MESP changes at the Li+ nucleus quantify cation-π binding electronic effects.
• Predicted cell potentials (Vcell) for LIBs using calculated adsorption energies.
• Coronene, circumbiphenyl, C42H16, and C50H18 ('carbon nanoflake' systems) are proposed as promising anode materials for LIBs.