Synthesis and electrochemical properties of V2O5•nH2O compound with reduced graphene oxide/polyvinyl alcohol film as the free-standing cathode for coin-typed aqueous Zn-ion batteries

Recently aqueous zinc-ion batteries (AZIBs) have been widely studied on the aspects of electrode materials and electrolytes, but it is still far from practical application. The limitation of AZIBs is that it is difficult to have both high specific capacity and good cycle stability. Herein, a free-standing cathode V(2)O(5)(center dot)nH(2)O/reduced graphene oxide-polyvinyl alcohol (denoted as V(2)O(5)(center dot)nH(2)O/rGO-PVA) film was synthesized by one-step hydrothermal method and vacuum filtration. As the cathode for the coin-typed AZIBs, the V(2)O(5)(center dot)nH(2)O/rGO-PVA film cathode delivers the ultrahigh capacity of 553 mA h g(-1) at the current density of 0.1 A g(-1). And the capacity is 194 mA h g(-1) at 0.5 A g(-1), after 300 cycles, it still remains 152 mA h g(-1). At the power density of 183 W.kg(-1), the high energy density is calculated as 354 Wh.kg(-1) based on the mass of the cathode. The energy storage mechanism was studied by some ex-situ characterizations as well. This work not only proposes a strategy for the synthesis of V(2)O(5)(center dot)nH(2)O/rGO-PVA film, but also demonstrates that the as-obtained free-standing cathode is beneficial to the assembly of coin-typed AZIBs and exhibits excellent electrochemical performance.