Highly flexible polypyrrole electrode with acanthosphere-like structures for energy storage and actuator applications

Polypyrrole (PPy) is a promising electrode material for energy storage devices and soft ionic actuators owing to its high theoretical capacitance, excellent electrolyte tolerance, and easy low-cost synthesis. However, large-scale production of flexible and self-standing pristine PPy electrodes with hierarchical structures and high capacitance for practical applications remains challenging. Herein, we report a large-scale flexible PPy membrane (15 cm in diameter) with acanthosphere-like vesicle structures (PPy-V) formed via nonionic surfactant–assisted interfacial polymerization. The unique structure could offer the PPy-V electrode more electrochemical active sites for high electrolyte loading and enable fast ion/electron transfer, resulting in improved electrochemical performance. The PPy-V electrode showed a high specific capacitance of 1434.21 mF cm−2 at a current density of 1 mA cm−2, with a capacitance retention rate of 87.2 % after 5000 cycles. The symmetrical supercapacitor assembled using the PPy-V electrode exhibited an energy density of 35.34 μW h cm−2 at a power density of 0.12 μW cm−2, and the curved actuator showed a reversible deformation with a low power consumption per unit strain of 7.45 mW cm−2 %−1. These superior properties of the PPy-V electrode with the bioinspired hierarchical structure make it a promising candidate for flexible supercapacitors and soft ionic actuators.