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.