Physicochemical and Electrochemical Properties of ZnCl ₂ /Propan-1,3-diol Deep Eutectic Solvent for Zinc-Ion Battery Electrolytes

As an environmentally benign solvent system, deep eutectic solvents (DESs) are of great significance in the field of sustainable development. This work pioneers a novel application of ZnCl2/propan-1,3-diol (1,3-PDO) DES as an environmentally friendly, low-cost, and safe electrolyte for zinc-ion batteries. The viscosity (η), conductivity (κ), and surface tension (γ) of DESs, and their correlations with ZnCl2 concentration, temperature, and hydrogen bonding strength are investigated. Furthermore, DES with a proper ZnCl2:1,3-PDO ratio exhibits a broadened operating temperature range and enhanced cycle life, owing to its well-balanced η, κ, and γ, as well as excellent thermal and chemical stability. The Zn||Zn symmetric cell with the ZnCl2/1,3-PDO (1:10) electrolyte achieves a cycle life of over 5000 h, demonstrating outstanding practical potential. This study provides important theoretical and data support for the application of ZnCl2/1,3-PDO DES as an electrolyte in zinc-ion batteries.