Tough Adhesive and Anti-Freezing Hydrogel Polymer Electrolyte with Ultra-Durable Electrochemistry for Extreme Deformations and Subzero Temperatures

Hydrogel polymer electrolytes (HGEs) are attracting significant attention due to their potential in the development of flexible and safe supercapacitors (SCs). However, the development of flexible supercapacitors based on HGE still faces numerous challenges, including issues such as interfacial delamination between the HGE/electrode under extreme deformations, and drastic performance deterioration at low temperatures. Herein, a tough adhesive polyacrylamide/H 3 PO 4 (PAM/H 3 PO 4 ) HGE was facilely prepared, exhibiting excellent flexibility, adhesion, ionic conductivity, and freeze resistance, which ensured close contact between the HGE and the polyaniline (PANI)-modified carbon cloth (C/PANI) electrode, thereby achieving a sandwich-type flexible supercapacitor with extremely low interface connection resistance and ultradurable electrochemistry under extreme deformations and subzero temperatures. Specifically, the interfacial adhesion energy between the HGE/electrode could reach up to 364 J/m 2 at 25 °C and maintain 269 J/m 2 even after exposure to −40 °C. The SC exhibited the capacitance retention rates of 98.42% and 96.78% after bending and twisting at 180° for 100,000 cycles, respectively. More impressively, the SC retains the capacitance value of 94.88% after 5000 cycles of 180° bending at −40 °C. This study proposed a simple and potentially commercialized HGE without any complex synthesis for constructing a highly flexible SC with excellent electrochemical stability under extreme mechanical and environmental conditions, while emphasizing the critical role of the HGE/electrode interface in enhancing the SC’s durability.