Graphyne as an anode material for Mg-ion batteries: A computational study

Abstract Although Li-ion batteries have different advantages, they suffer from short lifetime, high cost, and safety problems. The wide availability, multivalent character, and nontoxicity of magnesium suggest Mg-ion batteries (MIBs) as an alternative to Li-ion batteries. Here, we investigated the potential application of graphyne (as an alternative material to graphene) in the anode of MIBs at B3LYP and B3LYP-gCP-D3 levels. The adsorption energies of Mg and Mg2+ on graphyne were observed to be −6.1 and −223.6 kcal/mol, respectively. The dispersion term was predicted to be much more important for the Mg atom adsorption compared to the Mg2+ cation. The maximum energy barrier for the migration of Mg and Mg2+ over the graphyne surface was about 10.6 and 5.2 kcal/mol, respectively. The calculated cell voltage and specific storage capacity for graphyne respectively were 4.69 V and 558 mAh/g. The high cell voltage of MIBs is mostly attributed to the multivalent character of Mg atoms and strong cation–π interactions. Based on the results, the combination of high cell voltage, ultrahigh storage capacity, and good Mg mobility suggests graphyne as a promising anode substance in MIBs.