Na3V2(PO4)3 nanoparticles confined in functional carbon framework towards high-rate and ultralong-life sodium storage

Because of sodium abundance, sodium ion batteries attract a lot of attention for advanced energy storage applications. As the main member of cathodes, NASICON-type structured Na3V2(PO4)3 contributes excellent ion shuttling rate and structure stability. However, the low electrical conductivity (<10−4 S cm−1) of Na3V2(PO4)3 limits its application in high power field. Herein, the Na3V2(PO4)3 nanoparticles anchored in the carbon matrix are successfully prepared through using the V-based metal organic frameworks (MIL-101(V)). As expected, these small Na3V2(PO4)3 grains are uniformly distributed in Na3V2(PO4)3/carbon composite accompanying with the presence of 3D carbon framework. When used as cathode for sodium ion batteries, Na3V2(PO4)3/carbon composite delivers a considerable Na-storage capacity of 136.4 mAh g−1 at the current rate of 1 C and in the voltage range of 2.5–3.8 V. Even at the current rate of 5 C and 10 C, the 84.17% and 84.5% of capacity retentions are surprisingly kept after 1,000 cycles, verifying its ultra-long cycling life. Electrochemical impedance spectroscopy substantiates a decreased charge transfer resistance for Na3V2(PO4)3/carbon composite. Assisting with the detailed kinetic analysis, it is found that the enhanced surface-controlled behaviors mainly lead to the improvement of sodium-storage capability. The ex-situ scanning electron microscope and X-ray powder diffraction analysis demonstrates that unique architecture of as-prepared Na3V2(PO4)3/carbon composite significantly enhances structural stability during the fast cycling. This work provides insights on design of future advanced electrode materials for sodium ion batteries.