Ionic-Association-Assisted Viscoelastic Nylon Electrolytes Enable Synchronously Coupled Interface for Solid Batteries

Abstract

Electrolyte/electrode heterointerfaces activated by unhindered charge transfer play an important role in solid-state and flexible batteries. However, continuous electrochemical cycling and mechanical deformations cause structural dislocation and unwanted reactions. An important challenge is to ensure enduring accurate contact between the battery components. The customization of a highly viscoelastic polyamide (PA, nylon)-based solid electrolyte to address this key issue is presented. The approach involves the use of concentrated aqueous solutions of bis(trifluoromethane)sulfonimide lithium (LiTFSI) to structurally “unzip” and relink pristine hydrogen-bonded PA chains by bridged cation–anion association. This elaborately tailored crosslinking technique confers upon the resultant electrolyte a combination of the preferred mechanical characteristics including high viscoelasticity and reversible stretchability, together with outstanding electrochemical performance represented by high ion conductivity (2.7 × 10−4 S cm−1) and high anodic stability (>3 V vs Zn/Zn2+). Flexible batteries with a well-integrated configuration in which synchronous electrolyte/electrode movement guarantees intimate and compatible interfaces even during extreme deformations and electrochemical stimulations, are further demonstrated. These results reveal a promising opportunity to overcome the bottleneck caused by interfacial defects for next-generation solid batteries by reconstituting the structure of classical polymers and developing functional electrolytes.