High-Capacity Ion Batteries Based on Ti2C MXene and Borophene First Principles Calculations

In this paper, we report an ab initio study of a composite material based on Ti2C and borophene B-12 as an anode material for magnesium-ion batteries. The adsorption energy of Mg, specific capacitance, electrical conductivity, diffusion barriers, and open-circuit voltage for composite materials are calculated as functions of Mg concentration. It is found that the use of Ti2C as a substrate for borophene B-12 is energetically favorable; the binding energy of Ti2C with borophene is -1.87 eV/atom. The translation vectors of Ti2C and borophene B-12 differ by no more than 4% for in the X direction, and no more than 0.5% in the Y direction. The adsorption energy of Mg significantly exceeds the cohesive energy for bulk Mg. The energy barrier for the diffusion of Mg on the surface of borophene B-12 is similar to 262 meV. When the composite surface is completely covered with Mg ions, the specific capacity is 662.6 mAh g(-1) at an average open-circuit voltage of 0.55 V (relative to Mg/Mg+). The effect of reducing the resistance of borophene B-12 upon its binding to Ti2C is established. The resulting electrical conductivity of the composite Ti16C8B40 is 3.7 x 105 S/m, which is three times higher than the electrical conductivity of graphite. Thus, a composite material based on Ti2C and borophene B-12 is a promising anode material for magnesium-ion batteries.