Freestanding MoS2@Mn-NiO@rGO network composite electrode for high-energy flexible asymmetric supercapacitor applications

Two-dimensional molybdenum disulfide (2D MoS 2 ) has emerged as a promising electrode material for flexible supercapacitors (FSCs) due to its layered structure, excellent mechanical flexibility, large surface-to-volume ratio, and superior electrochemical performance. However, its low electrical conductivity and tendency toward layer restacking significantly limit its rate capability and long-term cyclability. Herein, we developed a three-dimensional (3D) heterostructure, MoS 2 @Mn-NiO@rGO, by uniformly growing MoS 2 mesospheres and Mn-NiO nanoparticles directly on the surface of reduced graphene oxide (rGO) sheets via a facile hydrothermal method. The MoS 2 @Mn-NiO@rGO electrode exhibited excellent mechanical flexibility and superior electrochemical properties compared with two control electrodes (MoS₂ and MoS 2 @rGO), obtaining a specific capacitance of ∼1094 F·g −1 at a current density of 1 A·g −1 . The superior performance of the 3D composite electrode is attributed to the synergistic effect of the distinctive interconnected network with abundant reaction sites and large enhancement of charge transport. A high mass loading (∼12.5 mg·cm −2 ) asymmetric supercapacitor (ASC) in the MoS 2 @Mn-NiO@rGO//AC configuration demonstrated a specific capacitance of ∼166.23 F·g −1 at 1 A·g −1 and excellent capacitance retention of ∼95.5% after 10,000 cycles at 3 A·g −1 . Moreover, the ASC device showed a high energy density of ∼51.94 Wh·kg −1 at a power density of ∼751 W·kg −1 . Besides, two ASC cells in series could power four LEDs (3 mm, 1.5 V each), thereby confirming the energy storage capability. The flexible ASC retained its initial specific capacitance at different bending angles, verifying their suitability as a high-performance power source for wearable applications.