Common ion effect enhanced Prussian blue analogues for aqueous ammonium ion storage

Abstract

In order to meet the growing demand of energy storage for the power grid, aqueous NH4+ batteries are attracting increasing attention as a promising alternative due to their environmental significance, abundant resources, and fast diffusion ability. In this work, FeFe(CN)6 (FeHCF) is synthesized as a cathode material for aqueous NH4+ batteries and Fe2(SO4)3 is utilized as a kind of functional additive in the electrolyte based on the "common ion effect"to enhance its electrochemical performance. The results indicate that the initial capacity of FeHCF is about 80 mA h g-1 with a coulombic efficiency of 97.8%. The retention rate can attain 96.3% within nearly 1000 cycles. Multivariate analysis methods are carried out to characterize the mechanism of FeHCF in aqueous NH4+ batteries. From the practical standpoint, FeHCF has outstanding cycling stability and rate capability, making it feasible to be applied in the power grid.