All-in-One flexible supercapacitor based on hydrogen bonds cross-linked organic gel electrolyte with anti-freezing and anti-pressure properties

Abstract

Hydrogel electrolytes have gained significant attention in the field of flexible supercapacitors (SCs) for their intrinsic safety, high flexibility, and superior ionic conductivity. However, the water-rich structures of traditional hydrogel electrolytes inevitably cause them to freeze at subfreezing temperatures, which limits the application of flexible supercapacitors at extremely cold temperatures. Here, a compressible and low-temperature resistant supercapacitor is fabricated containing multiple hydrogen bonds cross-linked N-(2-Hydroxyethyl) acrylamide (NHEA), acrylic acid (AA), ethylene glycol/water (EG/H2O), and H2SO4 organic gel electrolyte (OGE). The fabricated OGE exhibits high compressive stress (200 kPa), excellent shape recovery property, and high proton conductivity (62 mS/cm) even at −40 °C. Meanwhile, a reasonable assembly method of All-in-One SCs greatly reduces the contact resistance between the electrode and the gel electrolyte, progressing great capacitance (114 F/g) and flexibility. Remarkably, the device retains high capacitance retention under strong compressive stress (nearly 100%) and long-term circle (90.73% capacitance retention rate after 10,000 cycles). Furthermore, it retains near 76% capacitance at −40 °C, demonstrating the potential for applications in cold climates and high-altitude regions.