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

Abstract

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 (CaV3O7, CVO) is designed and synthesized by one step hydrothermal. The ex situ monitoring evidence that the Na+ can be reciprocal inserted/extracted into the NaCaxVyOz multi-phase (SCVO, includes NaVO3·1.9H2O and CaV3O7), 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|NaCF3SO3|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.