Hydrothermally synthesized nickel doped MnO2 nanocrystals for high-performance supercapacitor electrodes

Achieving superior electrochemical performance toward high energy storage in MnO 2 based supercapacitor is a crucial research objective. However, the limited electrical conductivity of MnO 2 results in poor charge - discharge kinetics and high internal resistance, consequently restricting the overall device performance, particularly at high rates. Herein present study, pristine and Ni-doped MnO 2 nanocrystals were synthesized using facile triethanolamine (TEA)-ethoxylate-assisted hydrothermal synthesis. The structural and morphological characteristics of Ni-doped MnO 2 were analyzed using various physicochemical characterization techniques viz. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared spectroscopy (FTIR), Brunauer Emmett Teller-Barrett Joyner Halenda (BET-BJH) surface analysis, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Using a 1 mol/L Na 2 SO 4 aqueous electrolyte, an electrochemical analysis of the fabricated electrodes made from pristine and Ni-doped MnO 2 was performed out using cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results revealed that, among the studied electrodes, the electrodes fabricated from 4 % Ni-doped MnO 2 exhibited a high specific capacitance of 432. 5 Fg(-1) at a scan rate of 5 mVs(-1) and excellent cyclic stability of 96.56 % over 2000 cycles at a high current density of 30 mAcm(-2). The 4 % Ni-doped MnO 2 showed high specific capacitance and energy density compared to pristine and other (2 % and 6 %) Ni-doped MnO 2 which can be attributed to the proper doping and high electrical conductivity. Furthermore, the as-fabricated asymmetric supercapacitor device using a 4 % Ni-doped MnO 2 sample as the positive electrode and activated charcoal (AC) as the negative electrode shows a maximum specific capacitance of 136.6 Fg(-1) at a current density of 2 mAcm(-2). The present study highlights the significance of the surfactant-assisted hydrothermal synthesis method and promising potential of the Ni-doped MnO 2 as a high-energy - density electrode material.