High-Capacity Ion Batteries Based on Ti 2 C MXene and Borophene First Principles Calculations.

In this paper, we report an ab initio study of a composite material based on Ti2C and borophene B12 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 B12 is energetically favorable; the binding energy of Ti2C with borophene is −1.87 eV/atom. The translation vectors of Ti2C and borophene B12 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 B12 is ~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 B12 upon its binding to Ti2C is established. The resulting electrical conductivity of the composite Ti16C8B40 is 3.7 × 105 S/m, which is three times higher than the electrical conductivity of graphite. Thus, a composite material based on Ti2C and borophene B12 is a promising anode material for magnesium-ion batteries. [ABSTRACT FROM AUTHOR]