Enhancement of Electrochemical Performance for Sodium-Ion Batteries by Eu-doped Na12(NbO)3(PO4)7 Anode Material

The cycling stability and rate performance of niobium-based anode materials remain constrained by slow sodium ion diffusion coefficient ( D _Na ⁺ ) and poor electronic conductivity, which limits their practical application in sodium-ion batteries (SIBs). Crystal structure modulation can significantly enhance D _Na ⁺ by expanding three-dimensional (3D) ion transport channels and optimizing Na ⁺ migration pathways. Herein, a series of Eu-doped phosphate materials, Na ₁₂ (NbO) _{3− x} Eu _x (PO ₄ ) ₇ with different doping amount of Eu, were synthesized for fabricating the anode of SIBs via a facile high-temperature solid-state method. Among them, the Na ₁₂ (NbO) _2.94 Eu _0.06 (PO ₄ ) ₇ ( Eu-0.06 ) anode material exhibits a D( _Na ⁺ ) of 10 ^− 10 -10 ^− 8 cm ² s ^− 1 and an impedance of 118.9 Ω. At a current density of 500 mA g ^− 1 , Eu-0.06 electrode demonstrates a high reversible specific capacity of 189.5 mA h g ^− 1 after 500 cycles with excellent capacity retention rate of 92.6%. In addition, the charge-discharge mechanism was proved by ex-situ XRD and ex-situ XPS analysis. The kinetic information obtained from cyclic voltammetry (CV) reveals that pseudocapacitive effects play a significant role in the specific capacity. As the results, we successfully developed Na ₁₂ (NbO) _2.94 Eu _0.06 (PO ₄ ) ₇ as an efficient anode material for high-performance SIBs which provided potential designing strategy based on the charge-discharge mechanism.