Hexagonal Boron Cluster As An Anode Material for Divalent-ion (Ca2+) Storage: A Theoretical Study

There has been always a persistent search for creating cheaper and efficient energy storage devices. After its discovery Li+ ion storage device has become the most preferred choice due to its high energy density. However, an ion storage device that can use Ca2+ ions instead of Li+ ions, will be much cheaper owing to the higher abundance of calcium. Realizing the need for developing novel ion storage devices, present study aims to investigate hexagonal boron (B-6) cluster's ability to store divalent Ca2+ ions. The calculated values of adsorption energies show that Ca2+ ions are well adsorbed in B-6 cluster and it reaches the maximum storage capacity when two ions are adsorbed into it with bi-pyramidal shape. We have used density functional theory (DFT) for our investigations. Both CaB6 and Ca2B6 have high specific capacities, with theoretical values 826 mAh/g and 1653 mAh/g respectively. Open circuit voltages (OCV) of the CaB6 and Ca2B6 are found to be 3.755 V and 2.993 V respectively.