V─O─Ti Bridge‐Bond Polarity Boosts Na + Migration in V‐Based Fluorophosphates for Fast Sodium Storage

Abstract

ABSTRACT Vanadium‐based fluorophosphates are promising high‐energy‐density cathodes for next‐generation sodium‐ion batteries (SIBs). However, the pronounced degradation of Na + diffusion at high voltage hinders their fast‐charging capability. Herein, a Ti 4+ ‐doping‐induced bridge‐bond‐polarity‐driven strategy is proposed to reshape the V electronic structure for facilitating V─O electron exchange. Correspondingly, voltage hysteresis, polarization, and structural distortion at high voltage are suppressed, accompanied by enhanced electronic conductivity. Meanwhile, the polar V─O─Ti bridge bonds expand the dominant one‐ and two‐dimensional Na + transport channels by inducing bridging‐O displacement, further boosting Na + migration capability. Therefore, Na 3 V 1.92 Ti 0.08 O(PO 4 ) 2 F 2 with V─O─Ti delivers high capacities of 121.8 and 62.1 mA h g −1 at 0.1C and 50C, respectively, while maintaining excellent cycling stability. Additionally, the 0.92‐Ah Na 3 V 1.92 Ti 0.08 O(PO 4 ) 2 F 2 //HC pouch cell exhibits 80% capacity retention after 1000 cycles at 1C. At the 9 Ah scale, the pouch cell achieves a high energy density of 154 Wh kg −1 . This synergistic reinforcement strategy driven by bridge‐bond polarity paves the way for sustainable high‐power polyanionic SIBs.