Tm³⁺-Doped Na₃V₂(PO₄)₃ Cathode: Accelerating Charge Transfer and Enhancing Lattice Stability for High-Performance...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Sodium vanadium phosphate (Na3V2(PO4)3) is a promising cathode material for sodium-ion batteries due to its high voltage and stability.
• Low electronic conductivity limits the practical application and high-rate performance of Na3V2(PO4)3.
• Developing strategies to enhance electronic conductivity is crucial for next-generation sodium-ion battery cathodes.

Purpose of the Study:

• To improve the electrochemical performance of Na3V2(PO4)3 by addressing its low electronic conductivity.
• To investigate the effect of Thulium (Tm3+) doping on the structural and electrochemical properties of Na3V2(PO4)3.
• To evaluate the high-rate capability and long-term cyclability of the doped material for sodium-ion batteries.

Main Methods:

• Synthesis of Thulium-doped Sodium Vanadium Phosphate coated with Carbon (Tm0.05-NVP@C) via a doping strategy.
• Electrochemical characterization including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.
• Theoretical calculations (e.g., density functional theory) and in situ X-ray diffraction analysis to understand doping effects and phase transformations.

Main Results:

• Tm3+ doping effectively narrows the electronic bandgap and reduces Na+ migration energy barriers in Na3V2(PO4)3.
• The Tm0.05-NVP@C cathode achieved a high reversible capacity of 88.65 mAh g-1 at 40 C.
• Exceptional capacity retention of 79.64% was maintained after 2500 cycles at 10 C, demonstrating enhanced long-term cyclability.
• In situ XRD confirmed reversible biphasic transformation during cycling, indicating structural integrity.

Conclusions:

• Thulium (Tm3+) doping is an effective strategy to enhance the electronic conductivity and electrochemical performance of NASICON-type cathodes.
• The Tm0.05-NVP@C material exhibits superior rate capability and cycle life, making it a viable candidate for advanced sodium-ion batteries.
• This study provides valuable insights for designing next-generation Na3V2(PO4)3-based cathodes with improved performance characteristics.