Flexible Freestanding Conductive Nanopaper Based on PPy:PSS Nanocellulose Composite for Supercapacitors with High Performance

A freestanding, binder-free flexible polypyrrole: polystyrene sulfonate/cellulose nanopaper (PPy:PSS/CNP) electrode is successfully fabricated by a low-cost, simple, and fast vacuum filtration method for the first time. The hierarchical structure of CNP with high surface area and good mechanical strength not only provides a high electroactive region and shortens the diffusion distance of electrolyte ions, but also mitigates the volumetric expansion/shrinkage of the PPy during the charging/discharging process. The optimized PPy:PSS/CNP exhibits a high areal specific capacitance of 3.8 F cm −2 (corresponding to 475 F cm −3 and 240 F g −1 ) at 10 mV s −1 and good cycling stability (80.9% capacitance retention after 5000 cycles). The cyclic voltammetry curves of PPy:PSS/CNP at different bending angles indicate prominent flexibility and electrochemical stability of the electrode. Moreover, a symmetric supercapacitor device is assembled and delivers a high areal energy density of 122 µ cm −2 (15 W h cm −3 ) at a power density of 4.4 mW cm −2 (550 mW cm −3 ), which is superior to other cellulose-based materials. The combination of high supercapacitive performance, flexibility, easy fabrication, and cheapness of the PPy: PSS/CNP electrodes offers great potential for developing the next generation of green and economical portable and wearable consumer electronics.