Core/Double-Shell Structured Na3V2(PO4)2F3@C Nanocomposite as the High Power and Long Lifespan Cathode for Sodium-Ion Batteries.

NASICON-structured Na3V2(PO4)2F3 is considered as a potentially high-capacity cathode material for Na-ion batteries; however, its poor rate capability and insufficient cyclability remain a challenge for battery applications. To address this issue, we designed and successfully synthesized a core/double-shell structured Na3V2(PO4)2F3@C nanocomposite (Na3V2(PO4)2F3@CD) by in situ carbon coating and embedding the Na3V2(PO4)2F3 nanoparticles in ordered mesoporous carbon framework. Benefiting from the sufficient electrochemically available interfaces and abundant electronic/ionic pathways, this Na3V2(PO4)2F3@CD material demonstrated superior Na+-storage performance with a high reversible capacity of 120 mA h g-1 at a moderate current of 1 C, a strong high-rate capability with 63 mA h g-1 at an extremely high rate of 100 C, and a long-cycle lifespan with 65% capacity retention over 5000 cycles. These superior electrochemical performances remained stable when the Na3V2(PO4)2F3@CD cathode was used in a full cell, suggesting a promising application of the material for high rate and long lifespan sodium-ion batteries. Moreover, the architectural design and synthetic method developed in this work may provide a new avenue to create high performance Na+-host materials for a wide range of electric energy storage applications.