Glycerol-Modified Methylcellulose Polyacrylamide Antifreezing Hydrogel Electrolyte for Flexible and Efficient Electrochromic Zinc Ion Battery

Abstract This work addresses critical challenges in the practical application of rechargeable, flexible electrochromic zinc-ion batteries. Conventional systems often suffer from hydrogen evolution at the zinc anode and the formation of dendrites and various side products due to excessive water molecules, leading to performance degradation, particularly under low-temperature conditions. To overcome these limitations, an antifreezing hydrogel electrolyte, designated as the MC-PAM-Gly hydrogel, was developed using glycerol as a cryoprotectant. Subsequently, the MC-PAM-Gly gel electrolyte was combined with a Prussian blue cathode material and a zinc anode to fabricate an electrochromic zinc-ion battery. The device demonstrated stable operation even at −20 °C, exhibiting outstanding freezing resistance, electrochromic performance, and energy storage capabilities. At room temperature, the device achieved an optical transmittance modulation of 55.8% and a high coloration efficiency of 173.3 cm2/C, alongside excellent cycling stability. After 1000 cycles, it retained 75.3% of its optical performance and maintained an area capacity of 60%. Notably, the areal capacity showed only minimal degradation under mechanical deformation, such as bending and twisting, indicating superior mechanical robustness. This study provides an effective material strategy and design concept for developing high-performance zinc-ion batteries with enhanced environmental adaptability.