Synthesis of 3D nanoflower-like mesoporous NiCo₂O₄ N-doped CNTs nanocomposite for solid-state hybrid supercapacitor; efficient material for the positive electrode

In this research work, we report a novel method for developing ternary NiCo₂O₄ compounds using deep eutectic solvents (DESs) and a strategy for improving their pseudocapacitive performance. NiCo₂O₄ composites with N-doped carbon nanotubes (NCNTs) were fabricated on Ni foam using a hydrothermal method. The electrochemical performance of the NiCo₂O₄ was altered with the change in the reaction temperature. The composite of NiCo₂O₄ and NCNTs demonstrated a maximum value of specific capacity of 303 mAh g⁻¹ at a scan rate of 5 mV s⁻¹. The specific capacity for the composite compound was 1.3-fold greater than that of the pristine NiCo₂O₄ sample. For practical applications, we constructed a flexible solid-state hybrid supercapacitor comprised of NiCo₂O₄/NCNTs//activated carbon (AC) cells with an excellent energy density of 12.31 Wh kg⁻¹, outstanding power density of 8.96 kW kg⁻¹, and tremendous electrode stability. The three-dimensional mesoporous nanoflowers and nanotubes-like nanostructures of NiCo₂O₄ are well-suited for use in hybrid devices as well as convenient for flexible electronic devices.