Unveiling the correlation between the thickness and uniformity of the hydroxyethyl cellulose film and its protective effect on the zinc electrode

The application of artificial solid-electrolyte interfacial (ASEI) layers on the surface of zinc (Zn) metal electrodes has been found to be beneficial for the cycling stability of aqueous zinc-ion batteries (AZIBs). In this work, we demonstrate that hydroxyethyl cellulose (HEC) films can act as effective ASEIs for Zn. Experimental and calculation results suggest that HEC interacts with hydrated Zn2+via hydroxyl and ether groups, which therefore avoids hydrogen evolution reactions and the formation of Zn hydroxide sulfate dendrites by limiting the access of water to the surface of the Zn metal electrode. The symmetric cell with the HEC-coated Zn electrodes (similar to 6 mu m thick) exhibited optimal cycling stability for 2700 hours at 5 mA cm-2 and 5 mA h cm-2, revealing the impact of the thickness and uniformity of the HEC films on the stability of the HEC protected Zn electrodes. Hydroxyethyl cellulose (HEC) films can act as effective artificial solid-electrolyte interfacial layers for Zn, and the thickness and uniformity of the HEC films play a decisive role in their protective performance.