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.