Trace Small Molecular/Nano‐Colloidal Multiscale Electrolyte Additives Enable Ultra‐Long Lifespan of Zinc Metal Anodes

Abstract

AbstractElectrolyte additives are efficient to improve the performance of aqueous zinc‐ion batteries (AZIBs), yet the current electrolyte additives are limited to fully water‐soluble additives (FWAs) and water‐insoluble additives (WIAs). Herein, trace slightly water‐soluble additives (SWAs) of zinc acetylacetonate (ZAA) were introduced to aqueous ZnSO4 electrolytes. The SWA system of ZAA is composed of a FWA part and a WIA part in a dynamic manner of dissolution equilibrium. The FWA part exists as soluble small molecules, which efficiently regulate Zn2+ ion solvation structure, while the WIA part exists as insoluble nano‐colloids, which in‐situ form a thick and robust solid electrolyte interface film on zinc metal anodes (ZMAs). Such small molecular/nano‐colloidal multiscale electrolyte additives of ZAA are capable to not only improve ionic conductivity and transference number but also inhibit corrosion, hydrogen evolution, and Zn dendrite on ZMAs. The SWA‐based Zn∥Zn half battery delivers a superb cumulative plating capacity of 15 Ah cm−2 under 1 mAh cm−2 and 20 mA cm−2, and the SWA‐based NH4V4O10∥Zn pouch cell obtains a capacity retention of 67.8% within 4000 cycles under 4 A g−1. The study provides innovative insights for rational design of electrolyte additives, which may pave the way for the practicality of AZIBs.