Unveiling Zn substitution and carbon nanotubes enwrapping in Na3V2(PO4)3 with high performance for sodium ion batteries: Experimental and theoretical study

NASICON-type Na3V2(PO4)(3) (NVP) is regarded as a prospective cathode material for sodium-ion batteries (SIBs). However, its electrochemical performance is restricted by poor intrinsic conductivity. Herein, we prepare Na3V2(PO4)(3) with Zn2+ ions doping via sol-gel method and enwrap it by carbon nanotubes (CNTs), in which CNTs act as conductive regent. The combined effects of CNTs and Zn2+ ions, especially for Na3.07V1.93Zn0.07(- PO4)(3)@CNTs composite, greatly improving the kinetic performance of pristine NVP. Specifically, Na3.07V1.93Zn0.07(PO4)(3)@CNTs composite possesses an initial capacity of 114.9 mAh g(-1), close to the theoretical value (117.6 mAh g(-1)). Moreover, the composite exhibits a discharge capacity of 86.9 mAh g(-1) at 15 C after 500 cycles with the retention rate of approximately 90.7%, demonstrating its high cyclic stability in long-cycling tests. Our theoretical results demonstrate that both the band gap and migration energy barrier can be reduced by Zn2+ substitution, which explains the improved electrical conductivity and ion diffusion rate. Overall, this design principle provides a promising method for fabricating Na3V2(PO4)(3) material as high-performance sodium-ion batteries.

Automated summary

By doping Zn2+ ions and encapsulating carbon nanotubes, the conductivity and ion diffusion rate of Na3V2(PO4)(3) material have been significantly improved, making it a promising cathode material for sodium-ion batteries.