Computational investigation of 2D 3d/4d hexagonal transition metal borides for metal-ion batteries

Abstract

Two-dimensional (2D) transition metal borides (MBs) with rich diversity and intrinsic high conductivity attract increasingly focus in energy storage fields. Herein, seven structures (Sc2B2, Ti2B2, V2B2, Cr2B2, Zr2B2, Nb2B2, Mo2B2) were screened from one interesting class of 2D hexagonal 3d/4d M2B2 monolayers to be promising anode materials for Li-/Mg-/Al-ion battery using first principles calculations. Phonon dispersions, energy calculations, configuration analyses, electronic structure analyses and ab initio molecular dynamics simulations confirm their high dynamic stability, strong adsorption capability and low volume change (< 7%) for Li/Mg/Al storage, and good thermostability with two layers of charge carriers. Furthermore, the high capacities (252–480/504–960/753–1442 mAh/g), low voltages (0.12–0.39/0.16–0.62/0.41–0.78 V), and ultra-low migration energy barriers (2.7–38.2/15.0–83.5/44.1–248.7 meV) in Li-/Mg-/Al-ion battery are proved. The performance of M2B2 monolayers in different ion batteries shows clear relationships with both the intrinsic nature of M and the electronegativity of charge carrier. For M2B2 monolayers in same period, the one with heavier M has higher dynamical stability, stronger bonding to charge carriers, and lower reaction voltage. In addition, a specific M2B2 monolayer shows stronger adsorption and slower conduction for the charge carrier with higher electronegativity. This work provides theoretical guidance for developing new MBs anode materials for ion batteries.