Constructing a Functional Fast‐Ion Conductor Interface for Vertically Aligned Titanium Boride Nanosheets to Achieve Superior Sodium‐Ion Storage Performances

Abstract Designing excellent anode materials to enhance the sluggish interfacial kinetics of Na + is a key challenge in improving the electrochemical performance of sodium‐ion batteries (SIBs). Herein, an ultra‐thin fast‐ionic conductor NaB 5 C coating TiB 2 nanoflowers with vertically aligned nanosheet arrays to form yolk–shell TiB 2 @NaB 5 C (TBNBC) nanospheres as an anode material for SIBs. The unique structure creates direct and short ion/electron transfer pathways and reserves enough space to prevent the uneven electrochemical reactions from TiB 2 nanosheets aggregation and stacking, thus ensuring the long‐term cycling stability of SIBs. Additionally, the NaB 5 C coating with fast‐ionic conductor functional interphase provides rapid Na + transport channels and effectively reduces the Na + de‐solvation barrier, accelerating Na + reaction kinetics. Furthermore, a homogeneous and robust solid electrolyte interphase (SEI) film including inorganic boron species and fluorine‐rich inner layer is constructed on the TBNBC electrode to delocalize stress and induce a uniform Na + flux, further promoting fast Na + interphase reaction kinetics. Consequently, the optimized composites achieve ultrastable cycling performances of 173 mAh g −1 over 5000 cycles at 10 A g −1 . More importantly, they also exhibit an outstanding capacity of 182.2 mAh g −1 at −20 °C. This work offers opportunities for the energy storage use of transition metal borides under extreme conditions.