Aqueous Electrolytes without a Zinc Salt Strategy Boosting the Cycling Stability of Prussian Blue Analogs in Aqueous Zinc-Based Batteries

Prussian blue analogues (PBAs) are considered as a promising cathode material for aqueous zinc-based batteries (AZBBs) due to their high discharge platform, moderate theoretical specific capacity, rigid three-dimensional skeleton structure, and low cost. However, the crystal structure of PBAs has strong electrostatic interaction with high-charge-density Zn2+ in the frequently used aqueous electrolytes for AZBBs, resulting in slow insertion kinetics of Zn2+ and poor cycle stability. Here, we reported the Zn/PBA batteries with Na2SO4 aqueous electrolytes in the absence of zinc salts, where the PBA cathode presented highly reversible embedding/removal of Na+ as well as the Zn anode showed reversible deposition/dissolution behavior of Zn2+. Significantly, our designed AZBBs without zinc salt in aqueous electrolytes delivered a higher specific capacity of 78 mAh g–1 at 0.1 A g–1 with a 99% Coulombic efficiency and a superior cycle stability of more than 1000 cycles at 1 A g–1 with 85.3% capacity retention. This work provided aqueous electrolytes without a zinc salt strategy to solve strong electrostatic interaction between the PBA cathode and zinc ions in AZBBs.