NASICON‐NaV0.25Al0.25Nb1.5(PO4)3/C: A High‐Rate and Robust Anode for Fast Charging and Long‐Life Sodium‐Ion Batteries

Abstract Nb‐based NAtrium Super Ionic CONductor (NASICON) frameworks (e.g., Nb 2 (PO 4 ) 3 and Na 1.5 V 0.5 Nb 1.5 (PO 4 ) 3 ) are emerging as the attractive Na‐ion anodes due to their lower intercalation voltage (≈1.4–1.2 V vs Na + /Na 0 ) and higher storage capacities (≈140–160 mAh g −1 ). However, their practical realization is limited by moderate cycle life and rate performances. In this work, a carbon‐coated NASICON‐NaV 0.25 Al 0.25 Nb 1.5 (PO 4 ) 3 (NaVAlNb/C) anode is unveiled for fast charging Na‐ion batteries. The incorporation of Al 3+ increases covalency of NASICON and creates disordered Na‐ion sublattice as observed by X‐ray diffraction and nuclear magnetic resonance spectroscopy measurements. Besides, the carbon‐coating and particle downsizing produces facile electron and ion percolation network. Accordingly, the NaVAlNb/C anode renders extraordinary rate performances (80 mAh g −1 at 20C) with longer cycling stability (95.2% retention after 5000 cycles at 10C). Climbing image nudged elastic band calculations reveal reduced Na‐ion migration barrier (202 meV) for NaVAlNb/C. Most importantly, a full Na‐ion cell based on Na 4 V 2 (PO 4 ) 3 cathode and NaVAlNb/C anode is demonstrated with a high‐power density (6493 W kg −1 ) and long‐cycle life (3000 cycles at 20C), which are far excellent compared to the state‐of‐the‐art NASICON‐based cells. This work demonstrates the significance of carbon coating and chemical tuning to tailor high‐rate NASICON anodes, which can produce fast‐charging Na‐ion batteries.