Hierarchical core-sheath polypyrrole@carbon nanotube/bacterial cellulose macrofibers with high electrochemical performance for all-solid-state supercapacitors

Fiber-based hybrid electrodes composed of carbon nanotube (CNT) and pseudocapacitance materials have gained great attention for wearable energy storage devices. However, it is still a challenge to obtain high capacitance fiber-based supercapacitor (FSC) with structurally optimized hybrid electrode. Herein, a flexible FSC with hierarchical core-sheath and porous structure is elaborately designed by self-assembly of multiple nanoscale polypyrrole@CNT/bacterial cellulose electrodes. The bacterial cellulose (BC) in the FSC not only efficiently prevent the aggregation of CNTs and significantly improve the wettability of supercapacitor, but also act as electrolyte nano-reservoirs, which can accelerate the diffusion of electrolyte ions and improve the electrochemical performance. The inner hierarchical core-sheath and porous structures significantly increase the specific surface area of the electrode and facilitate the ion transport resulting in considerably enhanced electrochemical properties. The assembled all-solid-state FSC exhibits high energy density of 6.8 mWh/cm³ (8.3 Wh/kg) at power density of 38.6 mW/cm³ (47.3 W/kg), power density of 391.7 mW/cm³ (454.5 W/kg) at energy density of 3.6 mWh/cm³ (4.2 Wh/kg), excellent cycling retention ability and bending ability. This high-performance FSC with well-designed structure fabricated by industrially viable wet-spinning technology, possessing great potential as the energy and power in various portable, miniaturized, and wearable electronic devices.