Polycyclic Aromatic Hydrocarbons As Prospective Cathodes For Aluminum Organic Batteries

Aluminum dual-ion batteries (DIBs) have been identified as a possible future alternative for lithium-ion batteries, possessing several attractive properties like high abundance, high energy density, and environmental friendly. Graphite and graphite-like materials are being explored to improve the cathodic performance in Al DIBs. Very recently, several organic materials with p-type redox activity are also gaining attention due to their flexibility, low cost, and easy availability for usage as electrodes in DIBs. In this work, we have evaluated four lightweight polycyclic aromatic hydrocarbons (PAHs) (pyrene, perylene, triphenylene, and coronene) as prospective cathode materials for Al DIBs using first-principles calculation. Binding energy calculations show favorable intercalation of AlCl4-, maintaining its tetrahedral geometry inside the flexible lattices and subsequent charge transfer from the PAH systems displaying their redox activity. The charge transfer also initiates semiconducting to metallic transformation ensuring the electronic conductivity during the redox reactions in Al DIBs. Pyrene and coronene are found to deliver good electrochemical performance with ultrahigh specific capacity. Triphenylene also exhibits good voltage (similar to 1.9 V) even at a lower specific capacity. The flexible arrangement of PAH molecules is expected to compensate for a slightly higher diffusion energy barrier values due to subsequent expansion with increasing concentration of AlCl4- intercalation. These results motivate us toward use of PAH materials and further exploration of similar organic materials as cathodes for Al DIBs.