Low Volume Fraction Co-Solvent Electrolyte Regulates the Solvation Structure for Highly Stable Zinc-Ion Batteries

Abstract

The development of zinc-ion batteries is impeded by parasitic reactions and dendrite formation on Zn anode. In this work, we address these problems using a low volume fraction 2-ethoxyethanol (ECS) co-solvent electrolyte. ECS molecules regulate the solvation structure of Zn2+, promote the generation of a solid electrolyte interface on the surface of the Zn anode, and play a crucial role in inhibiting parasitic reactions and Zn dendrites. Therefore, the Zn symmetric battery remains stable for 1700 h at 7 mA cm−2 and 7 mA h cm−2. In addition, the Zn||Cu asymmetric battery exhibits stability over 800 cycles at 1 mA cm−2 and 1 mA h cm−2, with an average Coulombic efficiency of 99.54%. Furthermore, the ECS co-solvent electrolyte can significantly enhance the performance of the full cell which achieves higher specific capacity and more stable cycling performance than the one with the aqueous electrolyte.

Keywords: Zn anode, Solvation structure, Co-solvent electrolyte, Solid electrolyte interface