Fe2(MoO4)3@Polyindole Nanocomposites for High-Performance All-Solid-State Symmetric Supercapacitors

Abstract

Synergistic architectures based on binary oxides and conducting polymers address the inherent limitations of individual components, thereby providing enhanced redox kinetics and structural stability for high-performance electrodes. Here, we explore the energy storage performance of Fe2(MoO4)3@polyindole (FMO@PIN) nanocomposites synthesized via in situ oxidative polymerization. The PFM2 (indole:FMO = 2:1 weight ratio) nanocomposite features a unique 3D criss-cross FMO framework with uniformly dispersed PIN globules. This optimized structure, along with multiple oxidation states of FMO, provides efficient conducting pathways and rich redox kinetics, enhancing the overall electrochemical performance. It achieves a high specific capacitance (Cs) of 567.6 F/g (at 5 mV/s) and outstanding stability, with 93.3% retention over 15,000 cycles at 5 A/g—performance metrics that significantly surpass those of its pristine constituents. Further, a symmetric device is assembled using PFM2 as both the counter and working electrodes with a PVA/H2SO4 gel electrolyte. The resulting symmetric device exhibits a Cs value of 288 F/g and a discharge time of 1296 s at 0.1 A/g. It delivers an impressive energy density of 32.23 Wh/kg at 90 W/kg. Three identical devices connected in series successfully powered a red light-emitting diode (LED) for up to 7 min, validating their potential as a compact, efficient energy storage solution.