Optimizing the electrolyte salt of aqueous zinc-ion batteries based on a high-performance calcium vanadate hydrate cathode material

Abstract

It is urgent to develop high-performance cathode materials for the emerging aqueous zinc-ion batteries with a facile strategy and optimize the related components. Herein, a Ca0.23V2O5·0.95H2O nanobelt cathode material with a rather large interlayer spacing of 13.0 Å is prepared via a one-step hydrothermal approach. The battery with this cathode material and 3 M Zn(CF3SO3)2 electrolyte displays high specific capacity (355.2 mAh g−1 at 0.2 A g−1), great rate capability (240.8 mAh g−1 at 5 A g−1), and excellent cyclability (97.7% capacity retention over 2000 cycles). Such superior performances are ascribed to fast electrochemical kinetics, outstanding electrode/electrolyte interface stability, and nearly dendrite-free characteristic. Instead, when ZnSO4 or Zn(ClO4)2 is used to replace Zn(CF3SO3)2, the electrochemical performances become much inferior, due to the slow electrochemical kinetics, inhomogeneous Zn stripping/plating process, and the formation of large dendrites and byproducts. This work not only discloses a high-performance cathode material for aqueous zinc-ion batteries but also offers a reference for the choice of electrolyte salt.