Conductive network enhanced self-assembled diphasic Prussian blue analogs for aqueous zinc-ion batteries†

Abstract

Zinc hexacyanoate (ZnHCF), one of the Prussian blue analogs (PBAs), is a promising cathode material for rechargeable aqueous batteries due to its easy synthesis and open framework. However, the low-capacity problem limits its further development. In this work, a low-cost and simple hydrothermal method is used to grow a diphasic Prussian blue composite material (ZnVHCF) on reduced graphene oxide (rGO), aiming to improve the specific capacity and conductivity of the electrode material by introducing vanadium-based Prussian blue and rGO conductive networks. Meanwhile, the electrolyte additive is utilized as a strategy to suppress the vanadium dissolution of cathode materials. Based on the synergistic effect of multiple strategies, the reduced graphene oxide modified vanadium–zinc diphasic Prussian blue (ZnVHCF@rGO) composite material exhibits excellent zinc storage performance. It shows a higher specific capacity of 152.3 mA h g⁻¹ at a current density of 0.1 A g⁻¹. In addition, the VO²⁺ sol–gel electrolyte additive provides additional capacity due to the electrochemical activity of V and delays material dissolution based on the principle of solvation equilibrium. The capacity reaches 84.1 mA h g⁻¹ at a current of 5 A g⁻¹, which is an improvement of 26.1%. And the cycling stability is improved by 25.2% after 300 cycles. This work provides new ideas for the design of high-performance PBA cathodes for AZIBs.