Single‐Ion‐Conducting Hydrogel Electrolytes Based on Slide‐Ring Pseudo‐Polyrotaxane for Ultralong‐Cycling Flexible Zinc‐Ion Batteries

• Published in: Advanced materials (Weinheim) 2023-09, Vol.35 (36), p.e2301996-n/a
• Main Authors: Xia, Huan, Xu, Gang, Cao, Xin, Miao, Chunyang, Zhang, Hanning, Chen, Pengyu, Zhou, Yang, Zhang, Wei, Sun, ZhengMing
• Format: Article
• Language: English
• Subjects: Electrochemical analysis; Electrolytes; Electrolytic cells; Hydrogels; Ion currents; Materials science; Mechanical properties; Polyacrylamide; Room temperature; Saline solutions; single‐ion‐conducting hydrogel electrolytes; slide‐ring structures; Strain; wearable electronics; Zinc; zinc dendrites; zinc‐ion batteries
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202301996

Flexible zinc‐ion batteries (ZIBs) with high capacity and long cycle stability are essential for wearable electronic devices. Hydrogel electrolytes have been developed to provide ion‐transfer channels while maintaining the integrity of ZIBs under mechanical strain. However, hydrogel matrices are typically swollen with aqueous salt solutions to increase ionic conductivity, which can hinder intimate contact with electrodes and reduce mechanical properties. To address this, a single‐Zn‐ion‐conducting hydrogel electrolyte (SIHE) is developed by integrating polyacrylamide network and pseudo‐polyrotaxane structure. The SIHE exhibits a high Zn2+ transference number of 0.923 and a high ionic conductivity of 22.4 mS cm−1 at room temperature. Symmetric batteries with SIHE demonstrate stable Zn plating/stripping performance for over 160 h, with a homogenous and smooth Zn deposition layer. Full cells with La‐V2O5 cathodes exhibit a high capacity of 439 mA h g−1 at 0.1 A g−1 and excellent capacity retention of 90.2% after 3500 cycles at 5 A g−1. Moreover, the flexible ZIBs display stable electrochemical performance under harsh conditions, such as bending, cutting, puncturing, and soaking. This work provides a simple design strategy for single‐ion‐conducting hydrogel electrolytes, which could pave the way for long‐life aqueous batteries. A single‐Zn2+‐conducting hydrogel electrolyte is developed by confining the anions between two ring‐shaped cyclodextrins to allow Zn2+ transfer along the outside of the rings. It delivers a large Zn2+ transference number of 0.923 and exhibits an excellent capacity retention of 90.2% after 3500 cycles in flexible zinc‐ion batteries at 5 A g−1.