Facile synthesis of a Ni-based NiCo₂O₄-PANI composite for ultrahigh specific capacitance

Composites of transition metal oxide and conductive polymer have shown great potential in optimizing the electrochemical performance of supercapacitors. Specifically, NiCo₂O₄/polyaniline (PANI) composites are especially promising, due to the synergetic effect of the two components. Here, we demonstrate the synthesis of a nickel foam-based NiCo₂O₄-PANI composite, where the PANI is polymerized in situ in aqueous acid, achieving co-doping of Ni²⁺ and Co²⁺ in the polymer. The synthesized composite was characterized using X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. Electrochemical studies indicate that the composite exhibits an ultrahigh specific capacitance of 15.5 F·cm⁻² (3108 F·g⁻¹) at a current density of 1 mA·cm⁻². In addition, the capacitance retention rate is 96.1% after 1000 charge-discharge cycles at 20 mA·cm⁻². Besides, such substrate-dependent design eliminates the electrode adhesion step in assembly compared to the substrate-free nanocomposite. A dual-electrode device made of NiCo₂O₄-PANI and activated charcoal exhibits a maximum energy density of 77.57 Wh·kg⁻¹ at 800 W·kg⁻¹. All these properties suggest that the materials and the synthesis route used for this NiCo₂O₄-PANI composite represent a promising strategy to make supercapacitor electrodes.