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

High Resolution Image Download MS PowerPoint Slide 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 (∼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.