Metallic B2Si monolayer as a flexible anode material for Li, Na and K-ion batteries: A first principles study

Silicon-based 2D materials have garnered significant attention as outstanding anodes of alkali metal ion batteries (MIBs); nevertheless, the poor electrical conductivity and mechanical property have severely hindered their practical application. In this work, we conducted a detailed first principles calculation to examine a newlydeveloped 2D silicon-boron binary compound (named B2Si) as the anode of MIBs. The B2Si anode harbors the intrinsic metallicity and exhibits low Li/Na/K diffusion barriers of 0.26, 0.14 and 0.09 eV, which makes a great contribution to the high rate performance. The storage capacities for Li/Na/K are predicted to be 1908.57, 583.48 and 431.97 mA h/g, respectively, superior to the commercial graphite anode. Moreover, the B2Si anode has good mechanical property and structural flexibility, which could avoid destroying its structure on the metal ion intercalation/deintercalation process. These fascinating features render the B2Si monolayer an exceptional anode of MIBs.