Conductive BSi4 monolayer with superior electrochemical performance for alkali metal ion batteries

Abstract

Silicon has received great interest in the development of next-generation metal ion batteries (MIBs) due to its extremely high capacity; however, the large volume expansion during intercalation process and intrinsically low electrical conductivity has severely hindered its electrochemical performance. In this work, we theoretically report that the recently-developed BSi4 monolayer is an appealing candidate as a flexible anode for high-performance MIBs. The BSi4 anode exhibits high mechanical and thermal stability with inherent metallicity, which is very advantageous for the fast electronic transport during battery cycle. All metal atoms are stably deposited on the anode surface with high ion mobility. The lowest diffusion barrier is predicted to be 0.33 eV for Li, 0.22 eV for Na, and 0.17 eV for K. Remarkably, the BSi4 anode possesses high Li/Na/K storage capacities of 1087.97, 1087.97 and 870.37 mA h/g, and low averaged open circuit voltages of 0.80, 0.52 and 0.63 V. Moreover, the BSi4 anode could withstand a large ultimate strain of 16.72 % (20.27 %) along zigzag (armchair) direction, showing a good mechanical flexibility.