Enhancing the Properties of Conductive Polymer Hydrogels by Freeze-Thaw Cycles for High-Performance Flexible Supercapacitors

We report that a postsynthesis physical process (freeze thaw cycles) can reform the microstructure of conductive polymer hydrogels from: clustered nanoparticles to interconnected nanosheets, leading to enhanced mechanical and electrochemical properties. The polyaniline poly(vinyl alcohol) hydrogel after five freeze thaw cycles (PPH-5) showed remarkable tensile strength (16.3 MPa), large elongation at break (407%), and high electrochemical capacitance (1053 F.g(-1)). The flexible supercapacitor based on PPH-5 provided a large capacitance (420 mF.cm(-2) and 210 F.g(-1)) and high energy density (18.7 W.h.kg(-1)), whose robustness was demonstrated by its 100% capacitance retention after 1000 galvanostatic charge discharge cycles or after 1000 mechanical folding cycles. The outstanding performance enables PPH-5 based supercapacitor as a promising power device for flexible electronics, which also demonstrates the merit of freeze thaw cycles for enhancing the performance of functional hydrogels.