NiFeCo Layered Double Hydroxide Derived from Co-MOF for Enhanced Energy Storage of Yarn-Shaped Supercapacitors

With the rapid development of flexible portable wearable gadgets, flexible energy storage units characterized by power output and mechanical compliance are highly demanded. This study proposes a strategy for preparing yarn-shaped supercapacitor (YSC) electrode materials based on cobalt-based metal-organic framework (Co-MOF) derived NiFeCo layered double hydroxide (NiFeCo-LDH). By in situ growth of Co-MOF as a self-sacrificial template and cobalt source on the surface of carbon nanotubes coated polyester yarn (CPY), hierarchical structured MOF-derived NiFeCo-LDH@CPY composite materials were prepared through a one-step hydrothermal method. Comprehensive analytical studies have shown that the NiFeCo-LDH@CPY composite, derived from Co-MOF precursors with a Ni²⁺/Fe³⁺ molar proportion of 2:1, reveals a multilayered sheet morphology accompanied by a specific surface area of 134.879 m² g^-1. The electrochemical assessment verifies that this electrode displays an areal capacitance of 5589.8 mF cm^-2 at a 1 mA cm^-2 current density, as well as a rate capability of 85.69%, outperforming the conventionally synthesized NiFeCo-LDH@CPY (3708.2 mF cm^-2, 36.15%). The fabricated symmetric yarn supercapacitor in quasi-solid-state configuration, incorporating this electrode material, functions across an operational voltage window spanning 0 to 1.6 V. It delivers the energy density of 17.35 μWh cm^-2 under a power density of 127.39 μW cm^-2, while preserving 80.05% of its pristine capacitance after enduring 10,000 charge-discharge cycles, and demonstrating mechanical pliability and structural robustness. This energy storage system additionally proves capable of illuminating LED matrices and energizing compact electronic apparatuses, thereby underscoring its considerable potential for deployment within wearable power applications.