Two-Step Carbon Coating and Zn/Si Codoping Engineering in Na ₃ V ₂ (PO ₄ ) ₃ : Constructing a Porous-Structured Cathode for High-Rate and Long-Life Sodium-Ion Batteries

High Resolution Image Download MS PowerPoint Slide The practical application of Na 3 V 2 (PO 4 ) 3 (NVP) is impeded by its inherent limitations of low intrinsic electronic conductivity and structural instability. To address these challenges, this study develops a porous cathode material featuring two-step carbon coating and Zn/Si-codoped NVP (NZnVPSi/TC). Electrochemical characterization reveals that Zn/Si codoping effectively enhances the specific capacity at low current rates, whereas the two-step carbon coating significantly improves high current rate performance. Notably, the three-dimensional conductive network and porous architecture synergistically boost the electrochemical performance of NZnVPSi/TC by facilitating enhanced electronic/ionic conductivity and accelerating the reaction kinetics. Consequently, the NZnVPSi/TC cathode delivers a remarkable specific capacity of 97.39 mAh g –1 at 10.0 C, with a capacity retention of 90.3% after 2000 cycles. Furthermore, even at a high rate of 20.0 C, the NZnVPSi/TC cathode maintains a specific capacity of 92.2 mAh g –1, accompanied by an excellent capacity retention of 91.2% after 2300 cycles. Finally, the full cell exhibits impressive stability (over 1400 cycles at 2.0 C), which underscores its significant potential for sodium-ion battery applications.