Eu ³⁺ Doping in Sodium Vanadium Phosphate: Synergistically Unlocking Fast Sodium Storage Kinetics and Stable Cycles

Sodium vanadium phosphate [Na 3 V 2 (PO 4 ) 3 ] stands out as an appealing cathode material for next-generation sodium-ion batteries owing to beneficial properties, such as high operating voltage, fast ion diffusion, and robust structural integrity. Nonetheless, its commercialization is challenged by an inherently poor electronic conductivity. Herein, a europium 3+ (Eu 3+ ) doping strategy was employed to synthesize a Na 3 V 1.95 Eu 0.05 (PO 4 ) 3 @C composite (Eu0.05-NVP@C), aiming to enhance its high-rate capability and cycling durability. Based on electrochemical kinetic studies and theoretical computations, the introduction of Eu 3+ into Eu0.05-NVP@C effectively reduces the band gap and activation energy for Na + migration, which synergistically promotes faster charge transfers. Moreover, the smaller integrated crystal orbital Hamilton population values for the V–O and Eu–O bonds indicate enhanced lattice cohesion. Consequently, the fabricated Eu0.05-NVP@C cathode exhibits a high reversible capacity of 97.63 mAh g –1 at 10C and achieves 93.60% capacity retention after 2000 cycles at 5C. In situ X-ray diffraction analysis further reveals the highly reversible biphasic transition reaction during cycling. This work not only validates Eu 3+ doping as an effective approach for optimizing NASICON-type cathodes but also offers strategic guidance for the development of next-generation Na 3 V 2 (PO 4 ) 3 -based electrodes with a superior rate performance and extended cycle life.