Facile synthesis of mesoporous NiFe2O4/CNTs nanocomposite cathode material for high performance asymmetric pseudocapacitors

Highlights: • Mesoporous NiFe₂O₄ nanoparticles with high BET surface area have been synthesized. • Content of MWCNTs has been optimized to obtain best NiFe₂O₄/CNT nanocomposites. • Electrochemical properties have been investigated in 2 M KOH aqueous electrolyte. • Best NiFe₂O₄/CNT nanocomposite shows specific capacitance of 1291 F g⁻¹ at 1 A g⁻¹. • An asymmetric supercapacitor has been designed using NiFe₂O₄/CNT nanocomposite. Morphology and synergistic effect of constituents are the two very important factors that greatly influence the physical, chemical and electrochemical properties of a composite material. In the present work, we report the enhanced electrochemical performance of mesoporous NiFe₂O₄ and multiwall carbon nanotubes (MWCNTs) nanocomposites synthesized via hexamethylene tetramine (HMT) assisted one-pot hydrothermal approach. The synthesized cubic phase spinel NiFe₂O₄ nanomaterial possesses high specific surface area (148 m²g⁻¹) with narrow mesopore size distribution. The effect of MWCNTs addition on the electrochemical performance of nanocomposite has been probed thoroughly in a normal three electrode configuration using 2 M KOH electrolyte at room temperature. Experimental results show that the addition of mere 5 mg MWCNTs into fixed NiFe₂O₄ precursors amount enhances the specific capacitance up to 1291 F g⁻¹ at 1 A g⁻¹, which is the highest reported value for NiFe₂O₄ nanocomposites so far. NiFe₂O₄/CNT nanocomposite exhibits small relaxation time constant (1.5 ms), good rate capability and capacitance retention of 81% over 500 charge-discharge cycles. This excellent performance can be assigned to high surface area, mesoporous structure of NiFe₂O₄ and conducting network formed by MWCNTs in the composite. Further, to evaluate the device performance of the composite, an asymmetric pseudocapacitor has been designed using NiFe₂O₄/CNT nanocomposite as a positive and N-doped graphene as a negative electrode material, respectively. Our designed asymmetric pseudocapacitor gives maximum energy density of 23 W h kg⁻¹ at power density of 872 W kg⁻¹. These promising results assert the potential of synthesized nanocomposite in the development of efficient practical high-capacitive energy storage devices.