2D Hierarchical Black Phosphorus‐Mn 2 O 3 Heterostructured Composites for High‐Performance Flexible Supercapacitors

ABSTRACT Flexible supercapacitors (FSCs) have shown great promise in next‐generation portable and wearable electronics. Still, their practical applications face challenges due to the narrow working potential window and low specific capacity of supercapacitors. In this regard, high‐performance flexible energy storage devices require the development of electrodes possessing improved conductivity, mechanical stability, and robust structural integrity. Here, an ex situ sonochemically assembled 2D hierarchical black phosphorus‐Mn 2 O 3 heterostructure (BPM) is engineered to synergistically improve charge storage capacity and device flexibility. The incorporation of black phosphorus (BP) into Mn 2 O 3 significantly facilitates charge transport, ion accessibility, and structural stability, and reinforces cycling stability. The optimized BPM‐37.5% electrode achieves a specific capacitance of 466 F g −1 at 3 A g −1 , retains 84% capacity after 8000 cycles, and reaches an energy density of 16.2 Wh kg −1 at 750 W kg −1 . The obtained electrochemical data indicate a hybrid charge‐storage mechanism, with a balance between surface redox reactions and ion intercalation within a capacitive‐diffusive framework. Moreover, an FSC device made from BPM material demonstrated an excellent energy density of 1.614 µWh cm −2 at a power density of 375 µW cm −2 and successfully powered LEDs and a scientific calculator under bending conditions.