Density functional theory study of defective silicenes as anode materials for lithium ion batteries.

In this contribution, we explore Li adsorption and diffusion on defective silicenes using first principles calculations. Defect formation energy (E) values showed that silicenes with 5105 and 5559 vacancy defects (Si-5559 and Si-5105) are likely to form during the fabrication process and E values are about one-third of graphenes. Calculation of Li adsorption energy indicated that Si-5559 and Si-5105 are better than pristine silicene for Li dispersion in the half-lithiated state. The diffusion barrier of Li on the surface of Si-5559 and Si-5105 and in the proximity of defected zone were obtained to be 0.24eV and 0.29eV, respectively. Diffusion barrier values show the easy motion of Li on these silicenes in comparison with defective graphenes. Ab-initio molecular dynamic (AIMD) simulations revealed that fully lithiated Si-5559 is not stable and can not accommodate lithium atoms. On the contrary, Si-5105 is stable and could store a certain amount of lithium atoms. The theoretical capacity of Si-5105 was calculated to be 664mAhg.