Boosting The Rate Capability And Cycle Life Of Zr-Substituted Na3v2(Po4)(3)/C Enwrapped On Carbon Nanotubes For Symmetric Na-Ion Batteries

Na3V2(PO4)(3) (NVP) has been deemed to be an ideal cathode candidate due to the high capacity but suffers from the intrinsic poor conductivity. Herein, we adopt a dual modification route of Zr substitution and carbon nanotubes (CNTs) enwrapping to improve the kinetic characteristics and stabilize the structural framework. The replacement of V3+ by Zr4+ is favorable to expanding the migration channels for Na+ diffusion and supporting the structure. Furthermore, Zr4+ substitution contributes to restraining the particle agglomeration and facilitating the uniform distribution. The evenly intertwined CNTs construct an efficient network and establish the beneficial connections for the adjacent Zr-doped NVP particles to accelerate the electronic conductivity significantly. Distinctively, the modified Na2.9V1.9Zr0.1(PO4)(3)/C@CNTs (Zr0.1-NVP/C@CNTs) exhibits a superior electrochemical performance: it delivers a capacity of 102.1 mAh g(-1) at 20 C with a retention of 86.3% after 10 00 cycles. Notably, it still reveals an outstanding capacity of 74.3 mAh g(-1) and remains 62.2 mAh g(-1) after 2000 cycles at 200 C, indicating a low capacity loss of 0.0081% per cycle. Moreover, the symmetric full cell constituted by Zr0.1-NVP/C@CNTs presents competitive practical applicability. Furthermore, the improved kinetic characteristics are demonstrated by multiple methods, indicating the significant improvement of conductivities resulted from the synergetic utility. (C) 2021 Elsevier Ltd. All rights reserved.