Predict low energy structures of BSi monolayer as high-performance Li/Na/K ion battery anode

Abstract

Silicon was regarded as a promising anode material for the next generation ion batteries due to the extremely high theoretical capacity (4200 mAh/g) and reasonable working potential. However, the dramatic volume change during the ion intercalation or deintercalation process as well as the poor electrical conductivity impedes its performance as an anode. Herein, we propose two dimensional (2D) puckered BSi anode to combine the advantages of silicon and boron-based materials. In this work, three novel 2D BSi monolayers are predicted: d1-BSi, c1-BSi, and c2-BSi, with d1-BSi, studied in detail as the anode of Li/Na/K ion batteries. The theoretical specific capacities are estimated at 1378, 1034, and 689 mAh/g for Li, Na, and K, respectively. The puckered structure benefits from its good rate capacity, with ion diffusion barriers along furrows at 0.37/0.24/0.14 eV for Li/Na/K. The averaged open circuit voltages (OCVs) are 0.53/0.53/0.87 V, respectively. The density of states and geometry optimization reveals that d1-BSi is a conductor during the intercalation of alkali metal atoms. Applying strain can decrease ion diffusion barriers efficiently for these ions. Our valuable results suggest that d1-BSi could be a promising anode candidate for Li/Na/K ion batteries.