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

The NASICON (Sodium super ion conductor)-type of Na 3 V 2 (PO 4 ) (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, Na 3 V 2 (PO 4 )-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 (NH 4 ) 4 Na 2 V 10 O 28 phase was formed. The 3D porous hydrogel with the (NH 4 ) 4 Na 2 [V 10 O 28 ]·10H 2 O 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 PO 4 3- groups may be distributed in the (NH 4 ) 4 Na 2 [V 10 O 28 ]·10H 2 O phase of the interlayer structure, leading to the enhanced electronic conductivity . The 3D porous Na 3 V 2 (PO 4 )/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.