Fe3+ Cross-Linked Polyaniline/Cellulose Nanofibril Hydrogels for High-Performance Flexible Solid-State Supercapacitors

Cellulose contains abundant oxygen-containing functional groups and can be used to fabricate hydrogel matrixes for supercapacitors (SCs). However, conventional bacterial cellulose-based SCs need a large amount of carbon materials with high electrical conductivity and mechanical strength to construct a three-dimensional network. Therefore, it is challenging to use cellulose as an electrode material with high electrochemical performance. Herein, Fe3+ is used to prepare cross-linked polyaniline/cellulose nanofibril hydrogels. The Fe3+ has two functions: it forms cross-links between cellulose nanofibril and polyaniline (PANI) through carboxylate anions and initiates aniline polymerization. The cross-links between the PANI and cellulose nanofibrils via Fe3+ form a porous and mechanically robust three-dimensional conductive hydrogel. The as-prepared PANI/cellulose nanofibril hydrogel as an SC electrode has a high areal capacitance of 3060 mF cm–2 and an energy density of 106 μW h cm–2 at 0.5 mA cm–2. Moreover, the convened flexible solid-state supercapacitor delivers a satisfactory areal capacitance of 185 mF cm–2 at 0.2 mA cm–2 and excellent flexibility. This green method extends the application of cellulose to SCs.