A low-transition-temperature electrolyte based on ethylene glycol for rechargeable zinc-ion batteries

• A LTT electrolyte for zinc-ion batteries is prepared by simply mixing and heating ethylene glycol (EG) with Zn(TFSI)₂. • Deep characterization of the LLT electrolyte using a combination of electrochemical and physicochemical methods is provided. • When tested in a Zn/KVO (K 0.5 V 2 O 5 ) cell the LLT electrolyte shows notable improvements in the cycling stability and an outstanding suppression of the dendrite growth. Zinc-ion batteries (ZIBs) offer promising energy storage solutions due to their high capacity, abundance and low cost of raw materials, and stability in air of zinc. Despite these advantages, ZIBs with aqueous electrolytes struggle with issues like dendrite formation, hydrogen evolution, and zinc corrosion. This study explores the use of low-transition-temperature (LTT) mixtures as electrolytes to address these critical issues of ZIBs. Novel LTT electrolytes at different molar ratios of Zn(TFSI)₂ and ethylene glycol (EG), chosen for their cost-effectiveness, were prepared. The LTT electrolytes were characterized, through spectroscopic and electrochemical methods, and the most promising one (Zn:EG 1:7) was further evaluated in a full cell by coupling Zn metal with a K⁺-doped vanadium oxide (K₀.₅V₂O₅, KVO) cathode. The full cell shows an excellent stability upon cycling and notable suppression of the dendritic growth, but limited capacities. Our electrolyte system holds significant potential for advancing ZIB technology if further developed.