Toward high stability of O3-type NaNi_1/3Fe_1/3Mn_1/3O₂ cathode material with zirconium substitution for advanced sodium-ion batteries

Abstract

We successfully synthesized a series of O3-type NaNi_1/3Fe_1/3Mn_1/3−xZr_xO₂ (x=0, 0.01, 0.02, 0.04) cathode materials by the solid-state reaction method. Energy dispersion spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy results confirmed the successful incorporation of Zr elements into the lattice to substitute Mn. Due to the introduction of Zr⁴⁺, the crystal structure modulation of O3-NaNi_1/3Fe_1/3Mn_1/3O₂ has been realized. By increasing the Zr⁴⁺ content, the width of the sodium diffusion layer expands, thereby facilitating the diffusion of sodium ions. Consequently, the material exhibits a remarkable enhancement in high-rate capability. At the same time, increasing the Zr⁴⁺ content results in a notable decrease in both the average bond length of TM−O and the thickness of the TMO₆ octahedron in the transition metal layer, resulting in a significant improvement in the cycling performance and structural stability of the cathode material. Additionally, the in-situ XRD results demonstrate that the optimized cathode composition of O3-NaNi_1/3Fe_1/3Mn_1/3-0.02Zr_0.02O₂ (NFMZ2) undergoes a reversible phase transition of O3→O3+ P3→P3→ O3 + P3→O3 during the charge-discharge process.

Keywords

crystal structure modulation / O3-NaNi_1/3Mn_1/3Fe_1/3O₂ / phase transition / sodium-ion battery / Zr⁴⁺ substitution

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2024 2024 The Authors. Carbon Neutralization published by Wenzhou University and John Wiley & Sons Australia, Ltd.