Synergetic optimization of p-type Ba2+ substitution and carbon nanotubes enwrapping in Na3V2(PO4)3: A superior cathode with high electrochemical and safety performance for half and full cells

Abstract

Na3V2(PO4)3 (NVP) has been deemed as a promising cathode because of high capacity and good stability. Nevertheless, poor intrinsic conductivity seriously limits its further application. Herein, partial Ba2+ substitution on V3+ site is introduced to modify NVP in terms of increasing cell volume due to larger ionic radius of Ba2+ and generating beneficial hole carriers derived from p-type doping. The expanded crystal channels efficiently facilitate the Na + migration and the hole carriers are beneficial for transfer charge to improve electronic conductivity. Ba2+ doping further enhances the structural stability due to the pillar effect, which has been proved by DSC measurement. The increase of exothermic peak temperature and decrease of heat release rate demonstrates the excellent thermal stability of NVBa0.07P@CNTs. Moreover, disordered carbon layer and enwrapped CNTs construct an effective network to provide abundant routes for electronic transportation. Notably, the optimized NVBa0.07P@CNTs delivers superior electrochemical performance in both half and full cells. It releases a capacity of 117.23 mA h g−1 at 0.1C and submits a capacity of 101.99 mA h g−1 with retention of 80% at 15 C over 2000 cycles. Even at 50 C, it still delivers a high value of 78.33 mA h g−1.