Sonochemically synthesized novel CNTs-PANI/CoNi(PO ₄ ) ₂ nanocomposites with enhanced electrochemical energy storage performance for asymmetric supercapacitor applications

Abstract

Carbon nanotubes (CNTs) were polymerized with polyaniline (PANI) via an in-situ polymerization approach. These functionalized CNTs (PANI-CNTs) were added in various concentrations to the sono-chemically synthesized Co-Ni binary transition metals phosphate (CoNi(PO 4 ) 2 ) to ultimately have their nanocomposites. Electron microscopy (SEM & HRTEM) was employed to reveal the morphology and microscopic features. The structural evaluation of metal phosphate and PANI/CNTs was done by X-ray diffractometer analysis, whereas chemical grafting of cobalt nickel phosphate (CoNi(PO 4 ) 2 ) was done by Fourier transformed infrared spectroscopy and Raman spectroscopy. The hierarchical structured CoNi(PO 4 ) 2 with 40 mg PANI/CNTs mass (CNP40) presented enhanced specific capacity of 1268 Cg −1 (2136 F g −1 at 1.5 F g −1 ) with excellent diffusive behavior (b = 0.5). A resulted hybrid supercapacitor device consisting of CNP40 as +ve electrode and activated carbon AC) as −ve electrode, presented excellent energy density of ∼87 Whkg −1 with good power density of 680 W kg −1 maintained to 32.9 W kg −1 (@ 20,400 W kg −1 ) with 37% rate performance, and excellent cyclic performance (∼100%) after 5000 charge-discharge cycles. Furthermore, capacitive-diffusive analysis revealed that the device showed 55% diffusive and 45% capacitive behaviour. This improved electrochemical performance might be attributed mainly to the uniform and hierarchical chemical grafted morphology of the novel combination of binary phosphates and PANI functionalized CNTs in the nanocomposite obtained via a rather different sonochemical approach.