2D Dumbbell Silicene as a High Storage Capacity and Fast Ion Diffusion Anode for Li-Ion Batteries.

First-principles calculations within DFT have been performed to investigate the use of a recently synthesized form of silicene, the dumbbell (DB) silicene as an anode material for Li-ion batteries (LiBs). The energetically most stable geometries for Li adsorption on DB silicene were investigated, and the energy barriers for Li-ion diffusion among the possible stable adsorption sites were calculated. We found that DB silicene can be lithiated up to a ratio of 1.05 Li per Si atom, resulting in a high storage capacity of 1002 mA h g and an average open-circuit potential of 0.38 V, which makes DB silicene suitable for applications as an anode in LiBs. The energy barrier for Li-ion diffusion was calculated to be as low as 0.19 eV, suggesting that the Li ions can easily diffuse on the entire DB silicene surface, decreasing the time for the charge/discharge process of the LiBs. Our detailed investigations show that the most stable form of two-dimensional silicon has characteristic features suitable for application in high-performance LiBs.