Facile synthesis of mesoporous NiFe₂ O₄/CNTs nanocomposite cathode material for high performance asymmetric pseudocapacitors

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 NiFe ₂ O ₄ and multiwall carbon nanotubes (MWCNTs) nanocomposites synthesized via hexamethylene tetramine (HMT) assisted one-pot hydrothermal approach. The synthesized cubic phase spinel NiFe ₂ O ₄ nanomaterial possesses high specific surface area (148 m ² g ⁻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 NiFe ₂ O ₄ precursors amount enhances the specific capacitance up to 1291 F g ⁻¹ at 1 A g ⁻¹ , which is the highest reported value for NiFe ₂ O ₄ nanocomposites so far. NiFe ₂ O ₄ /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 NiFe ₂ O ₄ 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 NiFe ₂ O ₄ /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.