First-Principles Design and Investigation of Siligraphene as a Potential Anode Material for Na-Ion Batteries

The continuous depletion of lithium resources has drawn great attention toward the development of nonlithium rechargeable batteries having electrode materials that prove to be promising in delivering advantages of cost-effectiveness, a high charge/discharge rate, and excellent storage capacity. Because of its planar honeycomb structure, a 2-D monolayer of siligraphene SiC7 has been explored as an electrode material for Na-ion batteries on the basis of its geometric, structural, and electrochemical properties by employing van der Waals corrected first-principles calculations based on density functional theory. Its dynamic and thermal stability is well validated using phonon dispersion spectra and ab initio molecular dynamics. A direct band gap of 0.7 eV presents it as a semiconductor material effective to be used as an electrode. Potential adsorption sites on the surface of SiC7 are studied for their effective storage capacity. Bader charge analysis revealed the charge transfer between the monolayers upon adsorption of Na ions. A high Na storage capacity of 696 mA h/g is obtained along with a low diffusion barrier of 0.8 eV, which further facilitates easy diffusivity of Na ions through the monolayers. Additionally, a working voltage of 0.84 V reveals that SiC7 will be a potential candidate for anodes in Na-ion batteries.