Abstract
Nickel-doped manganese dioxide (Ni-MnO2) synthesized by sol-gel method has been used as an electrode material for supercapacitors. The structure and electrochemical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectrometry (EIS). Results showed that the nickel-doped manganese dioxide sample exhibited irregular particles with the diameter of about 500 nm. The crystallographic structure of MnO2 was the poorly crystallized γ-MnO2. The doping ratio had a great influence on the electrochemical properties of the materials. When the molar ratio of Ni/Mn was 3/100, the specific capacitance of Ni-MnO2 achieved to 252.61 F/g. After 2000 charge/discharge cycles, the specific capacitance of Ni-MnO2 was still maintained at 74.36%, which was attributed to its excellent cycling stability.
Highlights
Supercapacitor is a new type of energy storage device that combines the advantages of both batteries and conventional capacitors
In order to increase the specific capacitance of the MnO2 electrode materials, MnO2 is usually compounded with other materials such as carbon materials or conductive polymers.[11-13]
Doping the transition metal element in the MnO2 lattice is an effective method to improve the electrochemical performance of the electrode materials.[8,14]
Summary
Supercapacitor is a new type of energy storage device that combines the advantages of both batteries and conventional capacitors. As an energy storage device, supercapacitor exhibits many advantages such as high power density, long cycle life, excellent reversibility and environmental friendliness.[1,2] It has been well developed in the field of electric vehicles with clean energy as the main energy source. The most widely used electrode materials include carbon materials[3,4], conductive polymers[5,6], transition metal oxides[7,8]. Transition metal oxides are considered to be preeminent electrode materials due to their large specific capacitance and fast redox kinetics. Doping the transition metal element in the MnO2 lattice is an effective method to improve the electrochemical performance of the electrode materials.[8,14]. The structures and electrochemical performances of obtained Ni-MnO2 were characterized by SEM, XRD, CV, GCD and EIS, respectively
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