Remarkable-cycling-performance anode for Li-ion battery: The bilayer β-bismuthene

Abstract

A good anode material for Li-ion batteries(LIBs) needs fast Li+ ion transfer rate and small volume expansion ratio(VER). The density functional calculations are carried to explore the performance of the two-dimensional bilayer β-bismuthene(β-Bi) as the LIB anode material. The phonon spectra without virtual frequency, intact structure at 300 K after dynamic operation can prove the thermodynamical stability of the bilayer β-Bi. The band gap of the bilayer β-Bi is only 0.06 eV, which indicates that the bilayer β-Bi changes from a semiconductor to a metal, thus, it should have good electrical conductivity. The diffusion energy barrier of 0.08 eV is rather small compared to most reported anode materials, and can enable the battery to achieve a very fast charge/discharge rate, which is critical to the cycle life of LIB. The average open circuit voltage (OCV) is only 0.28 V and can realize the higher cycle efficiency of bilayer β-Bi anode. Surprisingly, the maximum 7% VER is much smaller than that of other anodes and enables it to avoid the rapid capacity decline during the charge/discharge cycle. Our results will support conclusive evidence to prove that the bilayer β-Bi should be the promising LIB anode.