Freestanding conductive film based on polypyrrole/bacterial cellulose/graphene paper for flexible supercapacitor: large areal mass exhibits excellent areal capacitance

The development of polypyrrole (PPY) flexible supercapacitors has been recognized as one of the most effective strategies for preparing advanced flexible energy storage devices. However, they are still limited by low mass loading and poor areal capacitance during charge-discharge process. Here, freestanding conductive film is designed and prepared by PPY/bacterial cellulose (BC) nanofibers in combination with graphene (RGO) through a simple in situ polymerization and filtering method. The porous and flexible BC nanofiber is used as a substrate and template for successive polymerization of PPY, which is responsible for such a large areal mass of 13.5 mg cm⁻². Thus, the high areal capacitance of 3.66 F cm⁻² at 1 mA cm⁻² and 2.59 F cm⁻² at 50 mA cm⁻² are achieved. The assembled symmetric supercapacitor by coupling of two freestanding electrodes delivers high areal capacitance of 1.67 F cm⁻², high areal energy density of 0.23 mWh cm⁻² and a maximum power density of 23.5 mW cm⁻². Therefore, it is believed that this strategy holds great promise for design of freestanding conductive polymer electrodes on high performance flexible supercapacitors.