Abstract
A high-performance aqueous Li-ion hybrid capacitor (LHC) using sonochemically prepared copper
hexacyanoferrate (Cu-HCF) and sodium alginate-derived graphitic carbon (GC) nanoparticles are capable
of serving as positive and negative electrodes, respectively, is described in this report. The electrode
materials were prepared in a cost-effective manner and characterized using X-ray diffraction (XRD) and
Fourier transform-infrared spectroscopy (FT-IR). High-resolution transmission electron microscopy (HRTEM)
and surface area measurements revealed the formation of 30- to 60-nm Cu-HCF and 40- to 60-nm
GC particles with specific surface areas of 48 and 802 m2ge1, respectively. Electrochemical studies
including cyclic voltammetry (CV), galvanostatic charge-discharge (CD) analysis and electrochemical
impedance spectroscopy (EIS) using a three-electrode configuration confirmed the presence of intercalative
capacitance in the Cu-HCF electrode and double-layer capacitance in the GC electrode.
Furthermore, the constructed Cu-HCFkGC aqueous LHC system operates over a wide voltage window
(2.2 V) and delivers a high capacitance (63.64 F g1) and high energy density (42.78 Wh kg1) with a
good rate capability. These key features make the LHC system an ideal candidate for next-generation
electrochemical energy storage devices.
