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

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 Ca0.23V2O5·0.95 H2O nanobelt cathode material with a rather large interlayer spacing of 13.0 A 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.

Molten salt synthesis of α-MnO_(2)/Mn_(2)O_(3) nanocomposite as a high-performance cathode material for aqueous zinc-ion batteries

Thanks to low cost,high safety,and large energy density,aqueous zinc-ion batteries have attracted tremendous interest worldwide.However,it remains a challenge to develop high-performance cathode materials with an appropriate method that is easy to realize massive production.Herein,we use a molten salt method to synthesize nanostructured manganese oxides.The crystalline phases of the manganese oxides can be tuned by changing the amount of reduced graphene oxide added to the reactant mixture.It is found that the α-MnO_(2)/Mn_(2)O_(3) nanocomposite with the largest mass ratio of Mn_(2)O_(3) delivers the best electrochemical performances among all the products.And its rate capability and cyclability can be significantly improved by modifying the Zn anode with carbon black coating and nanocellulose binder.In this situation,the nanocomposite can deliver high discharging capacities of 322.1 and 213.6 mAh g^(-1) at 0.2 and 3 Ag^(-1),respectively.After 1000 cycles,it can retain 86.2% of the capacity at the 2 nd cycle.Thus,this nanocomposite holds great promise for practical applications.