Regulating Dielectric Desaturation Design for the Electric Double Layer of Zinc Anodes

For the rational design of the electric double layer (EDL) for stable Zn anodes in aqueous zinc-ion batteries, an effective and accurate descriptor is important and yet absent. In this work, we proposed a multiscale descriptor─dielectric desaturation (DDS) coefficient, considering molecular polarizability, excluded volume, adsorption coverage, and dielectric constant, which decouples the key parameters of interfacial concentration and potential difference in the Butler-Volmer equation. The DDS coefficient correlates with both the structural properties of the EDL and the dynamic process of Zn deposition and thus effectively guiding the electrolyte design of stable Zn anodes. A design-of-experiments screening from a library of aprotic solvents identified the optimal candidate with the highest DDS coefficient. Differential capacitance measurements and density functional theory calculations verified the ideal EDL structures, while in situ Raman, molecular dynamics simulations, and finite element analysis elucidated the uniform Zn deposition process, collectively demonstrating the effectiveness of the DDS coefficient. The constructed symmetric cells cycled for over 4000 h, and Zn||I2 full cells exhibited outstanding electrochemical performance with a high reversible capacity of 157.5 mAh g-1 at 10 A g-1 after 12000 cycles. These results demonstrate the relationship between the molecular-level coefficient and both the EDL structure and the Zn deposition process.