Adsorption of Li on single-layer silicene for anodes of Li-ion batteries.

We report an investigation of the interactions of Li with silicene. We find silicene to be a promising anode material for high energy density lithium-ion batteries. Based on first-principles calculations, we study the interaction between Li and silicene and explore the microscopic mechanism of Li storage on silicene. We find that Li ion is adsorbed on hollow sites at a very low concentration of less than 1.56%. At a high concentration of Li, the Li chains with up-down pairs on top sites become popular. With the formation of the Li chains, the local structure of silicene is modulated. In addition, the electronic states near the Fermi level are found to be renormalized. There is no obvious charge transfer from Li to Si, distinct from the C based materials, although the local charge distributions are polarized under the trapping of Li, implying a greater chemical interaction than that of the weak interaction with graphene. It is predicted that the capacity of silicene can reach 1196 mA h g-1 due to Li intercalation without the breaking of the Si-Si bonds.