A binary eutectic electrolyte design for high-temperature interface-compatible Zn-ion batteries

Abstract

The deterioration of aqueous zinc-ion batteries (AZIBs) is confronted with challenges such as unregulated Zn²⁺ diffusion, dendrite growth and severe decay in battery performance under harsh environments. Here, a design concept of eutectic electrolyte is presented by mixing long chain polymer molecules, polyethylene glycol dimethyl ether (PEGDME), with H₂O based on zinc trifluoromethyl sulfonate (Zn(OTf)₂), to reconstruct the Zn²⁺ solvated structure and in situ modified the adsorption layer on Zn electrode surface. Molecular dynamics simulations (MD), density functional theory (DFT) calculations were combined with experiment to prove that the long-chain polymer-PEGDME could effectively reduce side reactions, change the solvation structure of the electrolyte and priority absorbed on Zn(002), achieving a stable dendrite-free Zn anode. Due to the comprehensive regulation of solvation structure and zinc deposition by PEGDME, it can stably cycle for over 3200 h at room temperature at 0.5 mA/cm² and 0.5 mAh/cm². Even at high-temperature environments of 60 °C, it can steadily work for more than 800 cycles (1600 h). Improved cyclic stability and rate performance of aqueous Zn||VO₂ batteries in modified electrolyte were also achieved at both room and high temperatures. Beyond that, the demonstration of stable and high-capacity Zn||VO₂ pouch cells also implies its practical application.