Ag NPs-modified NiCoMn Layered Double Hydroxides Electrodes for High-Performance Asymmetric Supercapacitors

Abstract

The development of supercapacitor technology has been hindered by limitations in achieving both high power density and long cycle stability. Layered double hydroxides (LDHs) have emerged as promising candidates to address these challenges. In this study, we synthesized three distinct electrodes: NiCoMn LDH (LDH), Ag-citrate nanoparticles (Ag NPs), and a composite of Ag-citrate/NiCoMn LDH (Ag NPs/LDH), to explore their electrochemical performance. The structural and morphological characteristics of the synthesized materials were confirmed using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Among the materials, the Ag NPs/LDH composite exhibited superior electrochemical properties, with distinct anodic and cathodic peaks of higher current intensity and an expanded integrated area in the current-voltage curve. Additionally, impedance analysis revealed the lowest charge transfer resistance, indicating efficient charging and discharging processes. In addition, the Ag-NPs/NiCoMn composite exhibited a remarkable aerial-specific capacitance of 2764 mF.cm⁻² at 5 mA cm^-2 in a three-electrode configuration. Furthermore, in an Asymmetric supercapacitor (ASC) device configuration of AgNPs/LDH as a working electrode and Activated carbon as a working electrode (shorthand form AgNPs/LDH ||AC ASC), a specific capacitance of 1850 mF.cm^-2 at 5 mA.cm^-2 was achieved. Encouragingly, the AgNPs/LDH||AC ASC device exhibited an energy density of 0.593 mWhcm^-2 at a power density of 10 mW.cm^-2, maintaining a 0.175 mWhcm^-2 at a high-power density of 90 mWcm^-2, while retaining 102% of its capacitance after 4000 charging and discharging cycles. Overall, the AgNPs/LDH electrode material demonstrates significant potential for advancement in supercapacitor technology.