Hybrid Supercapacitor Based on Functionalized Ni-MOF Composite: Achieving Superior Power Density in Asymmetric Energy Storage Device

Abstract Hybrid energy storage systems have gained significant attention for addressing rising global energy demands by combining the complementary strengths of batteries and supercapacitors. Their practical implementation, however, requires simultaneous achievement of high energy and power densities, long-term cycling stability, and robust capacitance retention, criteria often limited by the inadequate functionality and structural instability of conventional electrode materials. In this work, a bromine-functionalized nickel-based MOF (Ni-HBTM) containing free carboxylic acid groups was synthesized to overcome these limitations. The Ni-HBTM metal–organic framework (MOF) delivered a specific capacitance of 620.22 F/g at 1 A/g in an alkaline electrolyte. When integrated with reduced graphene oxide (Ni-HBTM@rGO_20), the composite achieved an impressive specific capacitance of 1237.3 F/g at 1 A/g. An asymmetric supercapacitor (ASC) assembled using Ni-HBTM@rGO_20 as the positive electrode exhibited a specific capacitance of 174.04 F/g, energy density of 54.39 Wh/kg at 1 A/g, and a power density of 11,250 W/kg at 15 A/g current densities with 94% capacitance retention after 10,000 cycles, which is a significantly high specific capacitance and power density for Ni-MOF-based composites in comparable conditions. The ASC successfully powered light-emitting diodes (LEDs), demonstrating the potential of functionalized MOF-based materials to bridge the performance gap between batteries and supercapacitors and offering an approach toward next-generation all-solid-state energy storage devices.