Enhancing the electrochemical performance of Na₄MnV(PO₄)₃ cathode material by Zr substitution

The NASICON - structured Na₄MnV(PO₄)₃ is considered as a promising cathode material for sodium-ion batteries on account of its open three - dimensional framework, high redox potential, and excellent cycling stability. Nonetheless, the material's electrochemical performance is constrained by its inherently low electronic conductivity and the Jahn - Teller effect of Mn³⁺. In this work, a series of Na_4–2xMn_1-xZr_xV(PO₄)₃ (x = 0, 0.1, 0.125, 0.15, 0.175, 0.2, 0.3, 0.4, 0.5) materials were synthesized by substituting Zr at the Mn site to investigate the effects of Zr substitution on the cycling and rate performance of the NMVP material. XRD refinement was employed to ascertain the alterations in the crystal structure. In-situ XRD testing has also demonstrated that the substitution of Zr improves the stability of the material during high-voltage charge and discharge processes. The galvanostatic intermittent titration technique (GITT) test results demonstrate the variations in the diffusion coefficient of sodium-ions. 30 %Zr-NMVP sample exhibits excellent electrochemical performance. At a current density of 0.2 C, the initial discharge specific capacity reaches 89.26 mAh g^-1. After undergoing 100 cycles, the material maintains a capacity retention rate of 94.98 %. At 1 C, the initial discharge specific capacity is 85.32 mAh g^-1, and after 500 cycles, a reversible capacity of 74.30 mAh g^-1 is released, with a capacity retention rate of 86.03 %. In conclusion, Zr substitution can contribute to the improvement of the electrochemical performance of the NMVP material, providing the possibility of developing high - performance sodium-ion cathode materials in the future.