Anti-fatigue hydrogel electrolyte for all-flexible Zn-ion batteries

Abstract

Hydrogel electrolytes have been widely explored in Zn metal batteries for application in wearable electronics. While extensive studies have been conducted in optimizing the chemical structure and boosting the tensile elasticity, the mechanical stability of the hydrogel under repeated deformation is largely overlooked, leading to unsatisfactory performance at large cycling capacity. We systematically analyze the compressive fatigue-resistance properties of the hydrogel electrolyte, revealing the critical roles of the salts and copolymer matrix on crack initiation and propagation. We show that, on the premise of homogeneous Zn deposition, an improved anti-fatigue property is essential to achieve high-capacity Zn metal anodes. The optimal Zn(ClO4)2-polyacrylamide/chitosan hydrogel electrolyte (C-PAMCS) exhibits an unprecedented lifespan of 1500 h for Zn//Zn cells at a current density of 10 mA cm−2 and a high areal capacity of 10 mAh cm−2. We exemplify the potential application of C-PAMCS in all-flexible Zn-ion batteries enabled by a flexible current collector based on Ag nanowires embedded elastomer. This work provides the rationale under hydrogel electrolyte engineering for developing high-performance Zn anodes and derived energy storage devices.