Localized Eutectic Electrolytes for Stable Aqueous Zinc-Ion Batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) have been regarded as promising candidates for large-scale energy storage. However, the poor reversibility of Zn electrodeposition at low current densities still remains a great challenge in developing practical AZIBs. In this work, a localized eutectic electrolyte (LEE) is proposed by introducing trioxane to a baseline eutectic electrolyte, 2.0 M Zn(OTf)2 in water/sulfolane (50:50 vol %), for reversible Zn anodes under challenging conditions (low N/P ratios and low current densities). Trioxane serves to disperse the aqueous eutectic domain and construct a solvation-sheath-repelled inner Helmholtz plane, thus regulating charge transfer kinetics to enable further suppression of electrolyte corrosion and improved Zn morphology. Zn||Zn0.25V2O5·nH2O full cells with a low N/P ratio (≤4) and a low current density of 100 mA cathode-1 (corresponding to a 0.33 C rate) exhibit enhanced cycling stability and a prolonged lifespan (nearly 3 months) in the LEE.