A “Polymer-in-Salt” Solid Electrolyte Enabled by Fast Phase Transition Route for Stable Zn Batteries

Solid polymer electrolyte-based batteries show great promise because of their safe operating properties, wide voltage window and suitable flexibility. However, low ionic conductivity, low cation transfer number, weak oxidation/reduction resistance and low mechanical strength limit their implementation in Zn ion batteries. Here, w e developed a “polymer-in-salt” Zn²⁺-conductive solid electrolyte (denoted as 70% salt-SPE) constructed by a simple and fast phase transition method. The room-temperature ionic conductivity and the transfer number of the 70% salt-SPE reaches 1.6 mS cm⁻¹ and 0.78, respectively. Meanwhile, the ZnF2-rich inorganic/organic hybrid solid electrolyte interface is formed, and the stable voltage window reaches 9.35 V. In consequence, the Zn||Zn symmetric cell continuously cycles over 700 hours at current density of 2 mA cm⁻² and the Zn||Cu symmetric battery runs with Coulombic efficiency of >99%. The Zn||MnPBA full battery delivers a discharge specific capacity of 109 mAh g⁻¹ at room temperature and 190 mAh g⁻¹ at 60 °C. Meanwhile, impressive cyclic stability of 6000 cycles with capacity retention of 80% is achieved, which originates from the effectively optimized ion transport action and dendrite-free Zn plating/stripping.