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

• CNTs-enwrapped Na 3 V 2 (PO4) 3 with Zn 2+ ions doping is successfully synthesized via sol-gel method. • Initial discharge capacity of Zn0.07-NVP@CNTs is 114.9 mAh g −1 . • Retention rate of Zn0.07-NVP@CNTs is approximately 90.7% at 15 C after 500 cycles. • Broadened Na + migration channel is favorable to improving D Na+ . NASICON-type Na 3 V 2 (PO 4 ) 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 Na 3 V 2 (PO 4 ) 3 with Zn 2+ 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 Zn 2+ ions, especially for Na 3.07 V 1.93 Zn 0.07 (PO 4 ) 3 @CNTs composite, greatly improving the kinetic performance of pristine NVP. Specifically, Na 3.07 V 1.93 Zn 0.07 (PO 4 ) 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 Zn 2+ substitution, which explains the improved electrical conductivity and ion diffusion rate. Overall, this design principle provides a promising method for fabricating Na 3 V 2 (PO 4 ) 3 material as high-performance sodium-ion batteries.