Dual‐Ion Reconstruction of a LiF/NaF–N‐Rich Hybrid Interphase for Durable Silicon‐Carbon Anodes

ABSTRACT Silicon‐carbon anodes offer high capacity for lithium‐ion batteries, yet their cycling stability is limited by repeated solid‐electrolyte‐interphase (SEI) rupture during drastic volume changes. Herein, we introduce a NaNO 3 ‐DMSO additive into a conventional LiPF 6 /carbonate electrolyte to construct a durable LiF/NaF–N‐rich interphase on a porous silicon‐carbon composite (Si@pSC) through a dual‐ion cooperative mechanism. We reveal that DMSO enables NaNO 3 incorporation while preserving the carbonate‐rich Li + primary solvation sheath, with Na + strongly associating with PF 6 − and NO 3 − undergoing early interfacial reduction to seed nitrogen‐containing inorganic species. This dual‐ion synergy reconstructs the conventional carbonate‐containing SEI by incorporating LiF/NaF nanocrystalline domains and nitrate‐derived N‐containing species, thereby limiting persistent parasitic interfacial reactions while providing accelerated Li + transport pathways. Consequently, the optimized electrolyte enables Si@pSC half‐cells to deliver 365 mAh g −1 after 1000 cycles at 1 A g −1 , LFP||Si@pSC full cells retain 85.6% capacity after 1000 cycles at 2 C, and NCM811||Si@pSC full cells retain 95.4% capacity after 500 cycles at 2 C. Theoretical calculations further reveal that Na incorporation expands the fluoride lattice framework and lowers the Li + migration barrier from 0.56 to 0.42 eV. This dual‐ion interphase reconstruction strategy offers a practical pathway toward durable Si‐based anodes.