Unraveling the Function\nMechanism of N‑Doped\nCarbon-Encapsulated Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> Cathode toward High-Performance Sodium-Ion Battery with Ultrahigh\nCycling Stab

The NASICON-type Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> (NVP) is recognized as a potential cathode material\nfor Na-ion\nbatteries (SIBs). Nevertheless, its inherent small electronic conductivity\ninduces limited cycling stability and rate performance. Carbon coating,\nparticularly N-doped carbon, has been identified as an effective strategy\nto address these challenges. Hence, N-doped carbon-coated NVP was\nsuccessfully produced by a straightforward high-temperature solid-phase\nmethod, and the mechanism of N-doped carbon coating in regulating\nthe electrochemical kinetics of NVP was unraveled. The N-doped carbon\nlayer establishes a robust conductive network that interconnects the\nactive particles, facilitating electron transfer within the electrode.\nSEM images after cycling show that the uniform carbon coating mitigated\nNVP agglomeration, thereby reducing undesired side reactions between\nelectrode and electrolyte. The discharge capacities of NVP/N–C2\nelectrodes at 0.1, 0.2, 0.5, 1, 2, 5, and 10<i>C</i> reach\n116.0, 114.6, 112.6, 111, 108.7, 104.2, and 99.4 mAh g<sup>–1</sup>, respectively. Even at 20<i>C</i>, the discharge capacity\nremains up to 92.2 mAh g<sup>–1</sup>, which is approximately\n80% of the discharge capacity at 0.1<i>C</i>. When the rate\nreturns to 0.1<i>C</i>, the NVP/N–C2 cathode still\nexhibits a discharge capacity of 115.9 mAh g<sup>–1</sup>,\nshowing excellent electrochemical reversibility. This study presents\na viable approach for fabricating NVP with a N-doped carbon coating,\nshowcasing enhanced sodium storage properties.