Increased Cycleability for Reversible Zinc Electrodeposition for Dynamic Windows

The energy crisis is a grand challenge facing our world. In the U.S., buildings are responsible for ~40% of total energy consumption. Dynamic windows, which switch between dark and clear states upon application of a voltage, can result in an average of 10% energy savings in buildings. In previous research, it has been demonstrated that Zn-containing aqueous electrolytes used on transparent conducting glass electrodes facilitate fast, reversible, and color-neutral Zn electrodeposition over thousands of cycles in dynamic windows.^1,2 However, for commercialization applications, some important challenges still need to be overcome. Common challenges for reversible Zn electrodeposition on dynamic windows are dendritic growth, parasitic H₂ evolution, irreversible Zn-ion loses, and low cyclability.<br/>In this work, we improve the durability of 25 cm²Zn dynamic windows to 10,000 cycles and overcome all the above-mentioned challenges by using a unique electrolyte system. To achieve these results, we studied a series of electrolytes in different solvents and found relationships between the electrolyte and solvent compositions and the switching speed and cycleability of the devices. Proper control of the electrode-electrolyte interface results in the suppression of dendrite growth and enhances the reversibility of the Zn electrodeposition and stripping processes. The optimized electrolytes possess high Coulombic efficiency (&gt; 99%) and promote the formation of smooth and compact electrodeposit morphologies that efficiently block light. This study also allows us to design prototype two-electrode 100 cm² Zn dynamic windows that switch uniformly to &lt;2% within 30 s. Our results indicate that Zn is a promising metal for future practical dynamic windows based on reversible metal electrodeposition.<br/><br/><br/>References:<br/>1. Madu, D. C.; Lilo, M. V.; Thompson, A. A.; Pan, H.; Mcgehee, M. D.; Barile, C. J. Investigating Formate, Sulfate, and Halide Anions in Reversible Zinc Electrodeposition Dynamic Windows. <i>ACS Applied Materials & Interfaces </i><b>2022</b>. DOI: 10.1021/acsami.2c14893<br/>2. Islam, S. M.; Barile, C. J. Dynamic Windows Using Reversible Zinc Electrodeposition in Neutral Electrolytes with High Opacity and Excellent Resting Stability. <i>Advanced Energy Materials </i><b>2021</b>, <i>11</i> (22), 2100417, https://doi.org/10.1002/aenm.202100417.