Scalable synthesis of Na3V2(PO4)3/C with high safety and ultrahigh-rate performance for sodium-ion batteries

NASICON-type Na3V2(PO4)3 is a promising electrode material for developing advanced sodium-ion batteries. Preparing Na3V2(PO4)3 with good performance by a cost-effective and large-scale method is significant for industrial applications. In this work, a porous Na3V2(PO4)3/C cathode material with excellent electrochemical performance is successfully prepared by an agar-gel combined with freeze-drying method. The Na3V2(PO4)3/C cathode displayed specific capacities of 113.4 mAh·g−1, 107.0 mAh·g−1 and 87.1 mAh·g−1 at 0.1 C, 1 C and 10 C, respectively. For the first time, the 500-mAh soft-packed symmetrical sodium-ion batteries based on Na3V2(PO4)3/C electrodes are successfully fabricated. The 500-mAh symmetrical batteries exhibit outstanding low temperature performance with a capacity retention of 83% at 0 °C owing to the rapid sodium ion migration ability and structural stability of Na3V2(PO4)3/C. Moreover, the thermal runaway features are revealed by accelerating rate calorimetry (ARC) test for the first time. Thermal stability and safety of the symmetrical batteries are demonstrated to be better than lithium-ion batteries and some reported sodium-ion batteries. Our work makes it clear that the soft-packed symmetrical sodium ion batteries based on Na3V2(PO4)3/C have a prospect of practical application in high safety requirement fields.