Cellulose Nanofibers/Reduced Graphene Oxide/Polypyrrole Aerogel Electrodes for High-Capacitance Flexible All-Solid-State Supercapacitors

Flexible supercapacitors with considerable energy storage performance from green/sustainable materials have attracted significant attention in many fields, such as portable and wearable electronics. In this work, flexible cellulose nanofibers/reduced graphene oxide/polypyrrole (CNFs/rGO/PPy) aerogel electrodes with well-defined three-dimensional porous structures are prepared using citric acid-Fe3+ (CA-Fe3+) complexes as oxidant precursors to command the deposition of PPy. The in situ gradual release of Fe3+ leads to the formation of thin and uniform polypyrrole in the composites. A flexible all-solid-state supercapacitor is then prepared by the CNFs/rGO/PPy aerogel film electrode and poly(vinyl alcohol) (PVA)/H2SO4 gel electrolyte and separator. Due to the porous structure, high electrical conductivity, and remarkable wettability of the electrodes, the assembled supercapacitors show excellent electrochemical properties with maximum areal capacitance of 720 mF cm–2 (405 F g–1 for single electrode) at 0.25 mA cm–2 and good cycle stability (95% retention after 2000 cycles). The device with maximum energy density of 60.4 μW h cm–2 also exhibits nearly constant capacitance under different bending conditions, suggesting their great potential for applications in flexible electronics.