Sr-Doped NASICON-Structured Cathode with Enhanced Conductivity for Ultrafast and High-Stability Sodium-Ion Storage

NASICON-type phosphates are a promising cathode for sodium-ion batteries (SIBs) because of their suitable operating potential and open structural framework. Unfortunately, the poor rate performance is not satisfactorily limited by the low intrinsic electronic conductivity. Herein, we prepared a Na3V1.95Sr0.05(PO4)3 cathode by introducing Sr2+ into the crystal structure to achieve ultrafast and high-stability sodium-ion storage. The introduction of Sr2+ not only effectively enhances the ionic conductivity and electronic conductivity, leading to a stable crystal structure, but also promotes the generation of cavities and accordingly facilitates sodium-ion diffusion kinetics. As expected, Na3V1.95Sr0.05(PO4)3 demonstrates an excellent rate capacity of 92 mAh g–1 and a high retention of 82.1% since 10 000 cycles at 20C. This Sr2+ doping strategy provides an effective approach to designing SIBs with high power and long-term stability.