Construction of three-dimensional electronic interconnected Na3V2(PO4)3/C as cathode for sodium ion batteries

Abstract

The NASICON (Sodium super ion conductor)-type of Na3V2(PO4) (NVP) has a great potential for energy storage application due to its high voltage plateau, three-dimensional (3D) ionic diffusion channel, perfect thermal stability, and high structural robustness. Here, Na3V2(PO4)-based composites with 3D porous carbon skeleton structure were synthesized via hydrothermal methods. After a series of hydrolysis and polymerization processes, transparent colloid mainly containing (NH4)4Na2V10O28 phase was formed. The 3D porous hydrogel with the (NH4)4Na2[V10O28]·10H2O phase was produced by adjusting the reaction time. The product has a lamellar structure, and its ion is suitable to grow the nanosheets, and the present PO43- groups may be distributed in the (NH4)4Na2[V10O28]·10H2O phase of the interlayer structure, leading to the enhanced electronic conductivity. The 3D porous Na3V2(PO4)/C (NVP/C) with the size of 100–200 nm particles can be used as cathode for sodium ion batteries. The NVP/C delivers a specific capacity of 62.1 mAh g−1 at 10 C. The excellent stability of NVP/C can be obtained with 98% capacity retention after 140 cycles at 1 C. After 2000 cycles (5 C), the capacity is still 80.4 mAh g−1, with the capacity retention of about 86%. Our encouraging results may boost further studies of SIBs device by smart engineering of the electrode materials.