Borophene: A promising anode material offering high specific capacity and high rate capability for lithium-ion batteries

In this work, we adopt first-principles calculations and ab-initio molecular dynamics simulations to investigate the potential of borophene as an anode material for lithium-ion batteries. It is found that borophene has an adsorption energy to lithium atom of -1.12 eV, which is large enough to ensure a good lithium-borophene stability during the lithiation process. The fully lithiated phase of borophene is Li_0.75B, corresponding to a theoretical specific capacity of 1860 mA h g^-1, which is about 4 times larger than that of the commercial graphite anode (372 mA h g^-1). More excitingly, it is found that the energy barrier along the furrow of corrugated borophene is only 2.6 meV, which is much lower than those of other widely investigated anode materials such as phosphorene (80 meV) and Ti₃C₂ (70 meV). The finding suggests that lithium diffusion on borophene can be extremely fast. In the meantime, a strong directional anisotropy is observed for lithium diffusion, with a 325.1 meV barrier perpendicular to the furrow of borophene. This phenomenon is further proved by ab-initio molecular dynamics simulations at 300 K and the result shows the lithium atom can freely drift along the furrow, but seldom jumps to the neighboring furrows. Finally, borophene is found to exhibit metallic characteristics during the whole lithiation process, indicating that the material has an excellent electronic conductivity. The findings reported in this work suggest that borophene, as an anode material for lithium-ion batteries, has potential to drastically boost batteries' energy density and power density.