Fabrication of Antifreezing, Conductive, Polypyrrole-Based Hydrogels for Flexible All-in-One Supercapacitors

All-in-one hydrogel supercapacitors are promising flexible energy storage devices due to their good flexibility and interfacial stability. However, conventional all-in-one hydrogel supercapacitors (SCs) face fundamental limitations, including complex preparation methods and susceptibility to freezing or drying. Herein, we developed a safe and readily processable approach for fabricating a series of polyacrylamide/sodium carboxymethyl cellulose/polypyrrole (PAM/CMC/PPy) hydrogels tailored for flexible all-in-one SCs. The PAM/CMC/PPy hydrogels demonstrate favorable mechanical elasticity, with a fracture stress of 101 kPa at a strain of 1071%, an exceptional antifreezing point as low as −40.5 °C, and antidrying capability, with 95% water retention after 10 days in open air. Specifically, the optimized PAM/CMC/PPy2.0 SC achieves a high specific capacitance of 583.3 mF/cm2 and a superior energy density of 62.4 μWh/cm2 at a power density of 3600 μW/cm2. Notably, it retains its structural integrity and electrochemical performance under various deformations. More importantly, its excellent water-retention and antifreezing properties endow the device with remarkable stability across a broad temperature range of −40 to 50 °C, effectively mitigating freezing and drying issues. Furthermore, the SC device boasts an impressive cycle life, with 79% capacitance retention after 3000 cycles at room temperature and 73% retention following 3000 cycles at −20 °C. This study provides a feasible approach for realizing robust, flexible energy storage in harsh operational environments.