Bimetallic Manganese-Nickel Metal-Organic Framework Anchored Hexyl-Aminated Carbon Nanotube Hybrid as an Anodic Material for Solid-State Asymmetric Supercapacitors

With the increasing demand for advanced energy storage devices, supercapacitors (SCs) with high energy densities have been the focus of extensive research over the past few years. Improving the material properties of the electrodes in supercapacitors is crucial for enhancing their power and energy densities. This work proposes a hybrid framework for improving supercapacitor performance using synergetic interactions between heteromaterials. The as-synthesized hybrid electrode consists of hexyl-aminated carbon nanotubes (HA-CNTs) with high electrical conductivity and surface functionalities and a porous Mn-Ni(3-hydroxypyridine-2-carboxylic acid) metal-organic framework (Mn-Ni(3-HPCA) MOF) for fast ion diffusion. The Mn-Ni(3-HPCA) MOF/HA-CNT hybrid exhibited a remarkably high specific capacitance of 673.3 F/g at 0.25 A/g with a 72.3% capacitance retention at 10 A/g. This multicomponent electrode stores energy through both fast capacitive and faradic processes. The hybrid electrode delivers superior capacitive performance in the KOH electrolyte compared to that in the Na2SO4 electrolyte while revealing inferior cyclic durability in the alkaline electrolyte compared to that in the neutral electrolyte. The Mn-Ni(3-HPCA) MOF/HA-CNT hybrid and exfoliated graphene (XGnP) were investigated as the anode and cathode for fabricating a durable solid-state asymmetric supercapacitor using a KOH-loaded poly(acrylonitrile-co-1-vinylimidazole) gel electrolyte. The Mn-Ni(3-HPCA) MOF/HA-CNT//XGnP supercapacitor demonstrated an impressive energy density of 67.9 Wh kg(-1) at a power density of 300 W kg(-1) and possessed high cycling stability. This study could lead to the development of long-lasting hybrid materials for supercapacitors.