  Borophene, the boron atom analogue to graphene, being atomic thick have been
just recently experimentally fabricated. In this work, we employ
first-principles density functional theory calculations to investigate the
interaction of Ca, Mg, Na or Li atoms with single-layer and free-standing
borophene. We first identified the most stable binding sites and their
corresponding binding energies as well and then we gradually increased the ions
concentration. Our calculations predict strong binding energies of around 4.03
eV, 2.09 eV, 2.92 eV and 3.28 eV between the borophene substrate and Ca, Mg, Na
or Li ions, respectively. We found that the binding energy generally decreases
by increasing the ions content. Using the Bader charge analysis, we evaluate
the charge transfer between the adatoms and the borophene sheet. Our
investigation proposes the borophene as a 2D material with a remarkably high
capacity of around 800 mAh/g, 1960 mAh/g, 1380 mAh/g and 1720 mAh/g for Ca, Mg,
Na or Li ions storage, respectively. This study can be useful for the possible
application of borophene for the rechargeable ion batteries.
