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<p>Sodium-ion batteries (SIBs), as an emerging energy storage technology, have been recognized as one of the most promising alternatives to lithium-ion batteries (LIBs). Among various cathode materials, the NASICON-type Na<sub>4</sub>VMn(PO<sub>4</sub>)<sub>3</sub>(NVMP) composite material has garnered considerable attention owing to its distinctive 3D framework structure, high redox potential, stable crystal structure, and rapid Na<sup>+</sup> diffusion rate. Nevertheless, the practical application of NVMP cathodes is constrained by several inherent limitations, including inherently low electronic conductivity, Mn<sup>3+</sup> Jahn–Teller distortion, and structural degradation mechanisms, which collectively contribute to compromised rate capability and limited cycling durability. To tackle this challenge, an N-doped dual nano-carbon coating was applied to the NVMP material to enhance the conductivity of the composite. Building upon this foundation, a series of Na<sub>4</sub>VMn<sub>1-<i>x</i></sub>Cr<sub><i>x</i></sub>(PO<sub>4</sub>)<sub>3</sub>/NC@CNTs cathode materials (where <i>x</i> = 0, 0.25, 0.5, 0.75, and 1) were successfully prepared using the sol–gel method, enabling targeted regulation of Mn/Cr ratios for enhanced electrochemical performance. The N-doped dual nano-carbon coating is capable of forming carbon layer defects and active sites, as well as constructing a 3D conductive network structure, which can enhance the diffusion rate of Na<sup>+</sup> ions and shorten their transport path. The results indicate that the Na<sub>4</sub>VMn<sub>0.5</sub>Cr<sub>0.5</sub>(PO<sub>4</sub>)<sub>3</sub>/NC@CNTs cathode material demonstrates the highest discharge capacity, achieving 132.1 mAh·g<sup>−1</sup> when <i>x</i> = 0.5. Notably, the capacity decreases rapidly at high rates, potentially attributed to the collapse of the crystal structure and excessive polarization, resulting in a deterioration of the material’s electrochemical performance. The optimized Na<sub>4</sub>VCr(PO<sub>4</sub>)<sub>3</sub>/NC@CNTs (when <i>x</i> = 1) demonstrates exceptional rate performance with 91.2% capacity retention at 1C, accompanied by significantly reduced charge transfer resistance (Rct = 331.9 Ω). This study establishes a design paradigm for NASICON-type cathode materials through dual-transition metal synergistic doping and demonstrates the efficacy of Cr/Mn co-substitution in balancing ionic/electronic conductivity for next-generation high-power sodium-ion batteries.</p>

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Study on the synthesis and electrochemical performance of nitrogen-doped double carbon-coated Na4VMn1-xCrx(PO4)3/NC@CNTs

  • 期刊论文

  • 发表日期：

    2025年8月14日

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  • Cheng Xu,
  • Ke Liu,
  • Yong Lu,
  • Qi Xu

摘要

Sodium-ion batteries (SIBs), as an emerging energy storage technology, have been recognized as one of the most promising alternatives to lithium-ion batteries (LIBs). Among various cathode materials, the NASICON-type Na4VMn(PO4)3(NVMP) composite material has garnered considerable attention owing to its distinctive 3D framework structure, high redox potential, stable crystal structure, and rapid Na+ diffusion rate. Nevertheless, the practical application of NVMP cathodes is constrained by several inherent limitations, including inherently low electronic conductivity, Mn3+ Jahn–Teller distortion, and structural degradation mechanisms, which collectively contribute to compromised rate capability and limited cycling durability. To tackle this challenge, an N-doped dual nano-carbon coating was applied to the NVMP material to enhance the conductivity of the composite. Building upon this foundation, a series of Na4VMn1-xCrx(PO4)3/NC@CNTs cathode materials (where x = 0, 0.25, 0.5, 0.75, and 1) were successfully prepared using the sol–gel method, enabling targeted regulation of Mn/Cr ratios for enhanced electrochemical performance. The N-doped dual nano-carbon coating is capable of forming carbon layer defects and active sites, as well as constructing a 3D conductive network structure, which can enhance the diffusion rate of Na+ ions and shorten their transport path. The results indicate that the Na4VMn0.5Cr0.5(PO4)3/NC@CNTs cathode material demonstrates the highest discharge capacity, achieving 132.1 mAh·g−1 when x = 0.5. Notably, the capacity decreases rapidly at high rates, potentially attributed to the collapse of the crystal structure and excessive polarization, resulting in a deterioration of the material’s electrochemical performance. The optimized Na4VCr(PO4)3/NC@CNTs (when x = 1) demonstrates exceptional rate performance with 91.2% capacity retention at 1C, accompanied by significantly reduced charge transfer resistance (Rct = 331.9 Ω). This study establishes a design paradigm for NASICON-type cathode materials through dual-transition metal synergistic doping and demonstrates the efficacy of Cr/Mn co-substitution in balancing ionic/electronic conductivity for next-generation high-power sodium-ion batteries.