Freestanding bacterial cellulose–polypyrrole nanofibres paper electrodes for advanced energy storage devices

Advanced binder-free electrode materials with high mass-loading (~10 mg cm−2) have proved to be extremely important in determining the performance of pseudo-capacitors. In this work, freestanding and highly conductive paper electrodes with high mass loading in the range of 7–12 mg cm−2 are prepared using bacterial cellulose–polypyrrole nanofibres in combination with multi-walled carbon nanotubes via a simple vacuum-filtering method to realize highly stable and efficient pseudo-capacitors. A high capacitance of 2.43 F cm−2 at a mass of 11.23 mg cm−2 is achieved under standard reporting condition with these hybrid electrodes. By direct coupling of two membrane electrodes, symmetric supercapacitors can be easily fabricated without using any binders, conductive additives, and additional current collectors. The devices are able to offer large capacitance (590 mF cm−2) and excellent cycling stability (94.5% retention after 5000 cycles). Particularly, the electrode materials can be prepared in a large yield, which may open up new opportunities for development of low-cost and environmentally friendly paper-based energy-storage devices.