Significantly Improving the Initial Coulombic Efficiency of TiO₂ Anode for Sodium-Ion Batteries

Titanium dioxide (TiO₂) can serve as a candidate anode material for sodium-ion batteries (SIBs) with the merits of their low cost, abundance, and environment friendliness. However, its low initial Coulombic efficiency (ICE) and sluggish sodium-ion diffusion greatly limit its further practical applications. Herein, we report a one-step prepotassiation strategy to modify commercial TiO₂ by a spontaneous chemical reaction using potassium naphthalene (K-Nt). Prepotassiation effectively compensates for the irreversible Na loss and induces a homogeneous, dense, and robust artificial solid electrolyte interphase (SEI) on its surface. The well-distributed artificial SEI suppresses the excessive electrolyte decomposition, contributing to rapid interfacial kinetics and stable Na⁺ insertion/extraction. Therefore, such modified commercial TiO₂ anodes demonstrate significantly improved ICE (72.4%) and outstanding rate performance (176.4 mAh g^-1 at 5 A g^-1). This simple and efficient method for promoting ICEs and interfacial chemistry also demonstrates universality and practical value for other anodes in SIBs.