Reinforce effect with carbon interphase for high performance multi-phase V-based anode on sodium ion batteries

The vanadate materials have abundant valence, multiple [VO] n coordination polyhedron units and open frameworks structures, which are applied to anode materials . In order to investigate the phase stability of vanadate materials for anode electrode of sodium ion batteries (SIBs) at cycling, which lead specific capacity decay at a small current density, an orthorhombic calcium vanadium oxide (CaV 3 O 7 , CVO) is designed and synthesized by one step hydrothermal. The ex situ monitoring evidence that the Na + can be reciprocal inserted/extracted into the NaCa x V y O z multi-phase (SCVO, includes NaVO 3 ·1.9H 2 O and CaV 3 O 7 ), which is formed by activation at first several cycles. In addition, although the composition of the V-based anode material has been changed, the main structure of layers maintain stability at cycling. The carbon interphase of CVO@C could improve specific capacity and extend cycle life, obviously. The Na|NaCF 3 SO 3 |CVO@C exhibits a high specific capacity of 289.4 mAh g −1 and a cycling life up to 500 cycles at 0.2 A g −1 . Hence, this paper may offer a new prospective idea for anode protection and the multi-phase V-based materials designs in SIBs.