Robust double-network polyvinyl alcohol-polypyrrole hydrogels as high-performance electrodes for flexible supercapacitors.

The growing demands of flexible and wearable electronic devices boost the rapid development of flexible supercapacitors (FSCs). Conductive hydrogels are considered to be one type of promising electrode materials for FSCs due to their good processability and electrochemical properties. However, the poor mechanical properties of conductive hydrogels hinder their practical applications. Building robust cross-linked network structures is a feasible way to enhance their mechanical properties. Herein, the double-network polyvinyl alcohol (PVA)-polypyrrole (PPy) conductive hydrogels are synthesized by the freeze-thaw and in-situ polymerization method. The double-network structure not only enhances mechanical properties of the hydrogels, but also promotes their electrolyte ion transport. The maximum elongation at break of the optimized PVA-PPy hydrogels can reach 156.4%, and the specific capacitance is 1718.7 mF cm at 0.5 mA cm. Furthermore, the energy densities of the symmetrical PVA-PPy FSCs are 46.7 and 13.3 μWh cm at power densities of 200.0 and 2000.0 μW cm. Such excellent electrochemical performances and mechanical properties make the synthesized PVA-PPy hydrogels a promising candidate for FSCs.