Exploring the performance of T-graphene for the anode of Mg-ion and Ca-ion batteries: A first-principles study

Due to the growing need for high-capacity ion storage batteries, researchers are exploring new categories of electrode materials with superior electrochemical properties. In this investigation, a tetragonal symmetry of carbon named T-graphene has been taken into consideration as an anode material for Mg and Ca ion batteries for its superior electrical characteristics. To comprehend the adsorption behavior, charge transfer, and anodic properties of T-graphene, density functional theory has been employed. Initially, the most favorable adsorption sites for Mg/Ca insertion on the T-graphene have been identified and it found that bridge and octagonal hollow sites show high adsorption behavior with energy of about -1.99 and -4.86 eV, respectively. A significant amount of charge (Hirshfeld) about 0.24e and 0.79e transfer from Mg and Ca to T-graphene, respectively. When Mg/Ca is inserted, the electronic structure calculations demonstrate that T-graphene acts metallically. A very high specific capacity is found at about 1737.13 and 1985.30 mAh/g for Mg and Ca ion batteries, respectively. Moreover, the average open-circuit voltages for Mg are 0.65 V and 1.51 V for Ca. Therefore, it is assumed that T-graphene may be used as high-capacity anode material for Mg and Ca ion battery.