A Hydrogel Electrolyte with High Adaptability over a Wide Temperature Range and Mechanical Stress for Long‐Life Flexible Zinc‐Ion Batteries

Abstract

Flexible zinc-ion batteries have garnered significant attention in the realm of wearable technology. However, the instability of hydrogel electrolytes in a wide-temperature range and uncontrollable side reactions of the Zn electrode have become the main problems for practical applications. Herein, N,N-dimethylformamide (DMF) to design a binary solvent (H₂O-DMF) is introduced and combined it with polyacrylamide (PAM) and ZnSO₄ to synthesize a hydrogel electrolyte (denoted as PZD). The synergistic effect of DMF and PAM not only guides Zn²⁺ deposition on Zn(002) crystal plane and isolates H₂O from the Zn anode, but also breaks the hydrogen bonding network between water to improve the wide-temperature range stability of hydrogel electrolytes. Consequently, the symmetric cell utilizing PZD can stably cycle over 5600 h at 0.5 mA cm^- ²@0.5 mAh cm^-2. Furthermore, the Zn//PZD//MnO₂ full cell exhibits favorable wide-temperature range adaptability (for 16000 cycles at 3 A g^-1 under 25 °C, 750 cycles with 98 mAh g^-1 at 0.1 A g^-1 under -20 °C) and outstanding mechanical properties (for lighting up the LEDs under conditions of pressure, bending, cutting, and puncture). This work proposes a useful modification for designing a high-performance hydrogel electrolyte, which provides a reference for investigating the practical flexible aqueous batteries.