A sodium-templated structure search reveals a topological semimetal silicon anode for sodium-ion batteries

We report a porous Na–Si framework (NaSi₄) identified via a Na-templated crystal structure search, which integrates nontrivial topological electronic states with high-performance sodium-ion storage. NaSi₄ crystallizes in an orthorhombic architecture consisting of interpenetrating sp³-bonded silicon frameworks that form one-dimensional Na-filled channels. Upon Na removal, the resulting silicon host (Si₁₆) preserves the open-channel topology and structural integrity. Electronic structure calculations reveal symmetry-protected band crossings near the Fermi level, establishing Si₁₆ as a topological nodal-line semimetal with intrinsically robust electronic conductivity. Benefiting from the built-in conductivity and accessible diffusion channels, the Si₁₆ framework delivers a high reversible Na-storage capacity of ~ 239 mAh·g⁻¹ at an average insertion voltage of ~ 0.52 V (vs. Na/Na⁺). First-principles calculations further indicate strong Na binding, fast one-dimensional Na⁺ migration, and excellent structural stability. This work demonstrates a viable Na-templated design strategy for multifunctional silicon anodes and highlights the potential of coupling topological electronic states with energy-storage materials.