New phases of MBenes M₂B (M = Sc, Ti, and V) as high-capacity electrode materials for rechargeable magnesium ion batteries

Rechargeable magnesium ion batteries (MIBs) have attracted great interests as a prospective candidate for next generation large-scale energy storage systems owing to the low cost and high abundance of Mg resources. However, MIBs have been restricted by the lack of suitable electrode materials for a long term. Therefore, three new phases of two-dimensional transition metal borides (MBenes) including Sc₂B, Ti₂B and V₂B are explored as electrode candidates for MIBs. All the three M₂B (M = Sc, Ti, and V) with ground states of ferromagnetic configurations are proved dynamically and thermally stable by using phonon dispersions and molecular dynamics simulations. The results show that all M₂B phases have ultra-high specific capacity of 3192.813 mA h/g, 3018.414 mA h/g and 2853.953 mA h/g for Mg on Sc₂B, Ti₂B and V₂B, respectively. In addition, the M₂B monolayer only undergoes a small change in lattice constant with adsorption of single layer or multilayer ions. This work not only reports three new phases of M₂B with layered structure but also further provides useful information of MBenes as promising electrode candidates for high-performance metal ion batteries.