Quasi Three-Dimensional Tetragonal SiC Polymorphs as Efficient Anodes for Sodium-Ion Batteries

In the present work, we investigate, for the first time, quasi 3D porous tetragonal silicon-carbon polymorphs t(SiC)(12) and t(SiC)(20) on the basis of first-principles density functional theory calculations. The structural design of these q3-t(SiC)(12) and q3-t(SiC)(20) polymorphs follows an intuitive rational approach based on armchair nanotubes of a tetragonal SiC monolayer where C-C and Si-Si bonds are arranged in a paired configuration for retaining a 1:1 ratio of the two elements. Our calculations uncover that q3-t(SiC)(12) and q3-t(SiC)(20) polymorphs are thermally, dynamically, and mechanically stable with this lattice framework. The results demonstrate that the smaller polymorph q3-t(SiC)(12) shows a small band gap (similar to 0.59 eV), while the larger polymorph of q3-t(SiC)(20) displays a Dirac nodal line semimetal. Moreover, the 1D channels are favorable for accommodating Na ions with excellent (>300 mAh g(-1)) reversible theoretical capacities. Thus confirming potential suitability of the two porous polymorphs with an appropriate average voltage and vanishingly small volume change (<6%) as anodes for Na-ion batteries.

Automated summary

In this study, quasi 3D porous tetragonal silicon-carbon polymorphs t(SiC)(12) and t(SiC)(20) are investigated for the first time using first-principles density functional theory calculations. The structural design of these polymorphs is based on armchair nanotubes of a tetragonal SiC monolayer with a paired configuration of C-C and Si-Si bonds. The results show that both polymorphs are thermally, dynamically, and mechanically stable, with the smaller polymorph having a small band gap and the larger polymorph displaying a Dirac nodal line semimetal. The 1D channels of these polymorphs can accommodate Na ions with excellent reversible theoretical capacities, indicating their potential suitability as anodes for Na-ion batteries.