N-Doped Carbon Layer Modified Na3v2(Po4)3 as a High- Performance Cathode Material for Sodium Ion Batteries

Sodium super ion conductor (NASICON)-type Na3V2(PO4)3 (NVP) has been seen as an extremely potential cathode materials in sodium ion batteries (SIBs) for it owns many prominent merits like open 3D channel, high voltage platform, structural stability etc. Nevertheless, NVP is difficult to obtain excellent electrochemical performance at high rates with the defect of low electronic conductivity, which leads to the restriction of practical application. In this work, we used a simple sol-gel method synthesized a N-doped carbon layer modified Na3V2(PO4)3 composite material (NVP/NC) with urea as nitrogen source. And the further test proved that NVP/NC has better rate performance compared with NVP/C which has no N doping. The initial reversible capacity of NVP/NC can reached 109.18 mAh g-1 at 1 C, and the discharge specific capacity can still be 88.3 mAh g-1 even when the ultra-high current density is 50 C. In addition, NVP/NC also has excellent long cycle stability (the capacity retention rate still reach to 72.89% at 50 C after 8000 cycles, and the capacity reduction rate per revolution is only about 0.0034%). Because the N-doped carbon layer provides a surface channel for NVP electron transmission, the electronic conductivity is greatly enhanced, making the NVP/NC a better composite material for SBIs with higher rate performance. Hence, this work offers a practical process for solving the poor electronic conductivity issue of NVP.