In-Situ Constructing N,S-Codoped Carbon Heterointerface for High-Rate Cathode of Sodium-Ion Batteries

Na₃V₂(PO₄)₃ (NVP) is considered one of the promising choices for cathodes of sodium-ion batteries, but the poor conductivity resulted inferior rate performance limited the practical development of NVP cathodes. In this study, we successfully synthesized N/S dual-atom doped carbon coatings in situ through a simple one-step solid-state sintering method. The uniformly coated carbon layer can inhibit the agglomeration and growth of active materials during the sintering process, shorten the Na⁺ migration path, and increase the contact area with the electrolyte, thus facilitating rapid Na⁺ migration. Notably, the doping of N elements can alter the electron distribution of carbon coating, enhancing electron conductivity. Furthermore, the introduction of S elements in the carbon layer can induce the formation of stable C-S-C bonds in the molecular layer, expanding the interlayer spacing, which is beneficial for Na⁺ transport and storage. Therefore, the modified NVP@NSC composite provides a high specific capacity of 90.3 mAh g^-1 at a rate of 20 C, with a capacity retention rate of 94.4% after 8000 cycles, demonstrating excellent stability at high current densities. Moreover, the full cell exhibits remarkable electrochemical performance at 5 C. This research contributes to the practical development of NVP cathodes.