Ethanol Vapor-Induced Synthesis of Robust, High-Efficiency Zinc Ion Gel Electrolytes for Flexible Zn-Ion Batteries

Abstract

The evolution of flexible Zn-ion batteries (FZIBs) significantly hinges on the development of gel electrolytes, characterized by their mechanical properties, ionic conductivity, and environmentally friendly production processes. The prevailing challenge in this domain has been devising a gel electrolyte that encapsulates all these critical attributes effectively for practical application. This study presents a novel zinc ion gel (Zn-gel) electrolyte developed for FZIBs, synthesized via ethanol vapor-induced assembly of cellulose molecules. This innovative process fosters significant hydrogen bonding and ion-complexation with Zn2+ ions, resulting in a gel with exceptional mechanical strength (0.88 MPa), high ion transference (over 0.7), and impressive ionic conductivity (8.39 mS cm−1). The Zn-gel enables a FZIB to achieve a reversible capacity of 207.3 mAh g−1 and over 93% Coulombic efficiency after 500 cycles, devoid of liquid electrolyte. Highlighting a promising route for high-performance, eco-friendly gel electrolytes, this research advances flexible electronics and portable device applications, demonstrating the profound potential of bio-based polymers in enhancing energy storage technology.