Synergistic enhancement of sodium-ion storage performance in Na3V2(PO4)3/C cathode materials via Eu3+ doping and carbon coating

Abstract

In recent years, Na₃V₂(PO₄)₃(NVP) has emerged as a promising cathode material for sodium-ion batteries (SIBs) due to its stable NASICON-type framework, high theoretical capacity (∼117.6 mAhg⁻¹), and suitable operating voltage (∼3.4 V vs. Na⁺/Na). However, the practical application of NVP is hindered by its intrinsically low electronic conductivity, which significantly limits its electrochemical performance. This study systematically investigates the effects of Eu³⁺ doping on the crystal structure, electronic conductivity, and electrochemical properties of NVP. The results findings demonstrate that optimal Eu³⁺ doping effectively expands sodium-ion diffusion pathways while stabilizing the NASICON framework. Structural analyses (XRD, XPS) confirmed successful Eu³⁺ incorporation without altering the host framework. Electrochemically, the optimized 0.03Eu-NVP/C composite delivered a reversible capacity of 109.94 mAhg⁻¹ at 0.1C, outstanding cycling stability (93.69 % retention after 600 cycles at 1C), and remarkable long-term performance (92.15 % retention after 3000 cycles at 20C). Kinetic studies revealed enhanced Na⁺ diffusion coefficients and pseudocapacitive contributions, underscoring the efficacy of this dual-modification approach for high-performance sodium-ion batteries. Furthermore, the introduction of a carbon-coating layer substantially enhances the overall electronic conductivity of the material. The results conclusively demonstrate that Eu³⁺-doped Na₃V₂(PO₄)₃/C represents a highly promising cathode material for high-performance sodium-ion batteries.