Effect of surfactants on the electrochemical performance of iron hexacyanoferrate prepared by co-precipitation route for aqueous potassium-ion storage

As a promising electrode material for electrochemical energy storage, iron hexacyanoferrate (FeHCF) possesses diverse structures and properties that strongly relate to synthetic conditions. In this work, we synthesized FeHCFs by co-precipitation route and studied the influence of two surfactants (sodium citrate and potassium bitartrate) on the material characteristics and K⁺ storage properties of the resulting FeHCFs. Electrochemical measurements revealed that the FeHCF synthesized in the absence of surfactants exhibited superior performance to those synthesized in the presence of either surfactant due to reduced electrical resistivity and improved diffusion kinetics. The assembled all-solid-state symmetric device delivered an areal capacitance of 3.24 mF cm⁻², a wide potential window (1.4 V), an energy density of 3.17 μWh cm⁻², and a power density of 315.7 μW cm⁻² at a current density of 0.5 mA cm⁻¹, indicating its potential application for energy storage.