In‐Situ Construction of Solid Electrolyte Interphases with Gradient Zincophilicity for Wide Temperature Zinc Ion Batteries

A new hydrated eutectic electrolyte for zinc ion battery is designed to achieve ultra-long cycling under wide temperature conditions. Due to the dissociation-reduction of the eutectic molecules and SnI4, an organic–inorganic hybridized solid electrolyte interphase (SEI) layer is formed at zinc surface with the zincophile gradient, this special SEI can effectively suppress side reactions, regulate uniform Zn²⁺ deposition, and prolong the cell cycle life.

Abstract

Dendrite growth and parasitic side reactions on zinc (Zn) metal anode are major challenges limiting the practical application of aqueous zinc ion batteries (AZIBs), particularly under wide temperatures conditions. This study proposes a novel hydrated deep eutectic solvent based electrolyte by using ethylene glycol (EG) and SnI₄, enabling AZIBs to achieve excellent cycling life from −30 to 60 °C. Spectroscopic characterizations reveal H₂O molecules are effectively confined within the eutectic network due to the dual effects of Zn²⁺ coordination and EG hydrogen bonding, thereby weakening the free water activity and broadening the electrochemical window. Furthermore, resulting from the dissociation-reduction of the eutectic molecules and SnI₄, an organic-inorganic hybridized solid electrolyte interphase (SEI) layer is formed on Zn surface with the zincophile gradient, this gradient SEI layer effectively inhibits the hydrogen evolution reactions and regulates the oriented Zn deposition. The Zn//Zn  symmetric cell utilizing this electrolyte achieves remarkable cycling stability of over 7800 h at room temperature, over 6000 h at −30 °C, and 2500 h at 60 °C. This work provides insights into the new approach and formation mechanism of zincophile gradient SEI layer on Zn anode, which demonstrates significant potential for developing AZIBs with high stability under wide temperatures conditions.