Composition-optimized NiGa-LDH on MOF-derived and cobalt-nanoparticles-embedded carbon flakes for enhanced potassium-ion storage

Layered double hydroxides (LDHs), renowned for their distinct nanostructures, efficient ion channels, and high specific capacitance, are promising electrode materials for supercapacitors (SCs). However, commercial applications remain limited due to constraints in the rate capabilities and cycling. The synergistic effects of the composites can be leveraged by pairing LDHs with carbon materials to enhance the conductivity for better SC characteristics. Herein, flaky Zeolitic Imidazolate Framework(ZIF)-67 is deposited on carbon cloth and calcined to produce the MOF-derived composite of carbon nanosheet-embedded nano-cobalt particles (CPEC) on the surface of the carbon cloth. Afterward, NiGa-LDH with a controllable Ni to Ga ratio is synthesized on the CPEC to form a flower-like hierarchical nanostructure NiGa-LDH/CPEC@CC. Co nanoparticles act as nucleation sites for cohesive formation within the carbon cloth framework. Ni₂Ga₁-LDH/CPEC@CC has the best properties, such as a specific capacitance of 729.6F g⁻¹ at 1 mA cm⁻² and 97.3 % capacitance retention at 2 mA cm⁻². The asymmetric supercapacitor (ASC) consisting of Ni₂Ga₁-LDH/CPEC@CC//AC has an excellent energy density of 83.96 Wh kg⁻¹ with a power density of 80 W kg⁻¹. Density-functional theory (DFT) calculations of Ni₂Ga₁-LDH/CPEC@CC affirm a potassium ion adsorption energy of −2.127 eV and density of state (DOS) near the Fermi level. The study imparts theoretical and technical knowledge about the design of complex nanostructures from MOF precursors.

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