Bi-Cu Electrolytes with Aminocarboxylate Chelators for Reversible Metal Electrodeposition at High pH for Dynamic Windows

Abstract

Dynamic windows, which possess electronically tunable light transmission, increase both the energy efficiency and aesthetics of spaces such as buildings and automobiles. Although reversible metal electrodeposition affords a promising approach to constructing high-performing dynamic windows, the acidic nature of the aqueous electrolytes frequently used in these windows has prevented their commercialization due to tin-doped indium oxide (ITO) etching. In this manuscript, we design neutral and alkaline electrolytes that support the reversible electrodeposition of Bi and Cu at rates comparable to existing acidic electrolytes. In these electrolytes, Bi3+ and Cu2+ are solubilized by using aminocarboxylate chelating ligands. By evaluating a series of ligands with varying denticities, we demonstrate that N-(2-hydroxyethyl)ethylenedianmine-N,N’,N’-triacetic acid (ED3A-OH) provides the optimal metal ion binding strength that enhances solubility while simultaneously supporting rapid metal electrodeposition. These results allow us to design alkaline ED3A-OH electrolytes that are compatible with ITO even after four weeks of immersion at 85 °C. This manuscript thus demonstrates that chelating ligands can be utilized to design alkaline reversible metal electrodeposition electrolytes that support dynamic windows with robust shelf lives.