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<p>The polyanionic compound Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>O<sub>2</sub>F (NVPOF), featuring a stable three-dimensional framework structure, high theoretical specific capacity, and operating voltage, has been widely studied in recent years. However, its sluggish Na<sup>+</sup> diffusion kinetics and low electronic conductivity restrict the industrialization process of this material. Based on this, this study proposes a dual regulation strategy of carbon coating and heat treatment temperature regulation, revealing the synergistic mechanism of the two on the crystallinity and electrochemical performance of NVPOF. The NVPOF@C-400 and NVPOF@C-600 are successfully synthesized via <i>in-situ</i> dopamine hydrochloride coating coupled with heat treatments at 400 and 600 °C. Results show that carbon coating treatment at 600 °C remarkably enhances the material’s crystallinity and simultaneously increases its electronic conductivity by three orders of magnitude via the carbon layer’s conductive network. More crucially, the ∼4.5 nm carbon coating layer effectively restrains the abnormal growth and secondary crystallization aggregation of NVPOF grains at high temperatures, keeping the particle size uniformly stable at approximately 0.36 µm. This prevents ion transport obstruction due to grain coarsening, shortens the Na<sup>+</sup> diffusion pathway, and thus achieves a comprehensive improvement in the material’s electrochemical performance. NVPOF@C-600 delivers a high discharge capacity of 102.5 mAh g<sup>−1</sup> at 20 C, and retains 96.5% of its capacity even after 10,000 cycles. What is particularly striking is that the NVPOF@C-600//HC full-cell system performs exceptionally well, maintaining an impressive 89.3% capacity retention rate even after 9000 cycles. This study provides critical insights for the practical implementation of high-performance NVPOF cathodes.</p>

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Dual regulation strategy to construct robust and high-conductivity Na3V2(PO4)2O2F for ultra-long-life sodium-ion full cells

  • 期刊论文

  • 发表日期：

    2026年1月4日

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  • Yutian Chen,
  • Jingrui Sun,
  • Siyang Meng,
  • Hao Zhao,
  • Qi Wang,
  • Mai Li,
  • Huiyu He,
  • Huifang Li,
  • Xiaojun Wang,
  • Jianwei Li,
  • Zhiming Liu

摘要

The polyanionic compound Na3V2(PO4)2O2F (NVPOF), featuring a stable three-dimensional framework structure, high theoretical specific capacity, and operating voltage, has been widely studied in recent years. However, its sluggish Na+ diffusion kinetics and low electronic conductivity restrict the industrialization process of this material. Based on this, this study proposes a dual regulation strategy of carbon coating and heat treatment temperature regulation, revealing the synergistic mechanism of the two on the crystallinity and electrochemical performance of NVPOF. The NVPOF@C-400 and NVPOF@C-600 are successfully synthesized via in-situ dopamine hydrochloride coating coupled with heat treatments at 400 and 600 °C. Results show that carbon coating treatment at 600 °C remarkably enhances the material’s crystallinity and simultaneously increases its electronic conductivity by three orders of magnitude via the carbon layer’s conductive network. More crucially, the ∼4.5 nm carbon coating layer effectively restrains the abnormal growth and secondary crystallization aggregation of NVPOF grains at high temperatures, keeping the particle size uniformly stable at approximately 0.36 µm. This prevents ion transport obstruction due to grain coarsening, shortens the Na+ diffusion pathway, and thus achieves a comprehensive improvement in the material’s electrochemical performance. NVPOF@C-600 delivers a high discharge capacity of 102.5 mAh g−1 at 20 C, and retains 96.5% of its capacity even after 10,000 cycles. What is particularly striking is that the NVPOF@C-600//HC full-cell system performs exceptionally well, maintaining an impressive 89.3% capacity retention rate even after 9000 cycles. This study provides critical insights for the practical implementation of high-performance NVPOF cathodes.