Mechanically robust double-crosslinked network functionalized graphene/polyaniline stiff hydrogels for superior performance supercapacitors†
To extend the applications of supercapacitors, it is important and challenging to develop structural/stiff supercapacitors with excellent mechanical and electrochemical performance. In this work, high performance double-crosslinked network functionalized graphene/polyaniline stiff hydrogels (DN-PGH/PANIPA) have been successfully synthesized by polymerization of aniline in a confined functionalized graphene (PGH) hydrogel framework. A unique polyaniline (PANI) morphology with a combination of nanodot protrusions and nanofibers is obtained, where nanodot protrusions are tightly anchored to graphene walls and nanofiber crosslinked graphene sheets. The as-prepared DN-PGH/PANIPA hydrogel, consisting of a continuous conductive closely combined double-crosslinked network and PANI nanofibers, together with a high crystallization degree of the PANI structure, is both stiff and mechanically robust with a high tensile strength of 1.39 MPa at a small ruptured elongation of 0.42%. Meanwhile, the DN-PGH/PANIPA stiff hydrogels are assembled into symmetric supercapacitors and achieve a superior areal specific capacitance of 3488.3 mF cm−2 and a volumetric specific capacitance of 872 F cm−3, remarkable rate capability, and excellent cycling stability, resulting in a notable energy density of 155 μW h cm−2 at 200 μW cm−2 and an outstanding power density of 20 015 μW cm−2 at 67.5 μW h cm−2. This novel double-crosslinked network design strategy establishes a promising approach towards the development of other stiff electrode materials as high performance structural supercapacitors.