Monolayer, Bilayer, and Bulk BSi as Potential Anode Materials of Li-Ion Batteries

Monolayer, bilayer, and bulk BSi are studied to explore their application potential as anode materials of Li-ion batteries. Structural stability and metallicity are obtained in each case. The Li storage capacities of monolayer and bilayer BSi are 1378 and 689 mAh g⁻¹, respectively, with average open circuit voltages of 1.30 and 0.47 V as well as Li diffusion barriers of 0.48 and 0.27 eV. Bulk BSi realizes a layered structure in the presence of a small amount of Li and its Li diffusion barrier of 0.48 eV is identical to that of graphite and lower than that of bulk Si (0.58 eV). The Li storage capacity of bulk BSi is found to be 689 mAh g⁻¹, i. e., much higher than that of graphite (372 mAh g⁻¹). The volume expansion turns out to be 33 % and the chemical bonds remain intact at full lithiation, outperforming the 72 % volume expansion of bulk Si at the same capacity and thus pointing to excellent cyclability.