3D printable conductive polymer hydrogels with ultra-high conductivity and superior stretchability for free-standing elastic all-gel supercapacitors

Conductive polymer hydrogels (CPHs), especially poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) hydrogels, have become research hotspot because they demonstrate tremendous application potential in cutting-edge technologies such as flexible electrochemical energy storage, bioelectronics, and wearable electronics due to their unique electrical, electrochemical and mechanical properties. However, the existing gelation strategies generally fail to achieve excellent electrical and mechanical properties simultaneously in PEDOT:PSS hydrogels and limit their broad applications. Herein, an effective gelation strategy is developed to achieve a kind of free-standing PEDOT:PSS hydrogels by double-additive induced physical cross-linking. Through the interconnection and entanglement between conductive PEDOT nanofibril chains in the physical cross-linking network, the electrical, mechanical and electrochemical properties can be synergistically optimized. The resulting PEDOT:PSS hydrogels simultaneously show ultra-high electrical conductivity, excellent mechanical stretchability, high resilience, low Young’s moduli, superior swelling behavior, and extrusion 3D printability, demonstrating extensive applicability. As proof of concept applications, substrate-free, highly elastic all-gel supercapacitors (SCs) have been fabricated using the resulting PEDOT:PSS hydrogels as electrodes. The SCs exhibit simple structure, facile assembly process, high specific capacitance, excellent energy storage capacity, superior cyclic stability, and arbitrary deformability, holding great promise for wearable electronics.