The Synthesis and Characterization of Bioactive Carbon Material Supercapacitor Loaded with Nickel Hydroxide
Supercapacitor is an environmentally friendly energy storage device, which fills the gap between traditional capacitors and batteries, and its energy density and power density are higher than the battery [1]. Moreover, the supercapacitor has the characteristics of high charging and discharging efficiency and long cycle life. This makes it used in the electric vehicles, high powered weapons, standby power in electronic equipment, flash of industrial equipment and ignition device [2]. So it has great significance for the basic research, the development of electronic industry and the electric vehicle to carry out the supercapacitor electrode materials [3]. Here, we firstly prepared the activated carbon materials by carbonizing, activating the biological material, then prepared the nickel hydroxide/activated carbon composites by direct precipitation method, and studied the electrochemical properties of composite materials with different nickel hydroxide (Ni(OH)2) contents (the mass fraction). The results of cyclic voltammetry and constant current charge-discharge are that a small amount of Ni(OH)2 are mixed in the carbon surface and pores, the composite material has a good specific capacitance, stability, charging and discharging performance compared with the activated carbon. When the mass fraction of Ni(OH)2 is 12%, the supercapacitor exhibits the excellent electrochemical properties, its capacitance is up to 400.78F/g which improved 75.21% compared with the activated carbon’s capacitance (228.74F/g). 6mol/L potassium hydroxide (KOH) is used as an electrolyte, the capacitance is only reduced to 94.42% after conducting 1000 times cycle life tests. This means that the supercapacitor shows a good stability.
Preparation and Performance of Polypyrrole/Nitric Acid Activated Carbon Aerogel Nanocomposite Materials for Supercapacitors
: Polypyrrole (PPY)/nitric acid (HNO 3 ) activated carbon aerogel (HCA) composites are prepared through chemical oxidative polymerization with different PPY/HCA mass ratios. Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscope (SEM) were employed to investigate the components and morphology of the samples. The results demonstrate that the synthesized materials maintain the three-dimensional nanoporous structure of the carbon aerogel (CA); the activation by nitric acid and composition with PPY do not destroy the porous structure of the carbon aerogel and the complex still has the original three-dimensional nanoporous structure. Composites with different mass ratios (3 : 1, 2 : 1, 1 : 1, 1 : 2, 1 : 3) of PPY/ HCA were prepared and the electrochemical properties were measured by cyclic voltammetry, galvanostatic charge-discharge test, and electrochemical impedance spectroscopy. The results confirm that the PPY/HCA composite with a ratio of 1 : 1 exhibits the best electrochemical performances; it has a high specific capacitance of 336 F ∙ g － 1 , which is more than two times higher than that of CA (103 F ∙ g － 1 ); it also exhibits outstanding conductivity and cycling stability, retaining 91% of its initial capacitance after 2000 cycles. Therefore, this and deionized water as solvent. The mass percentage of reactions in solution was 30%, the molar ratio of R to C was held at a constant value of 500.
Dual functions of activated carbon in a positive electrode for MnO 2-based hybrid supercapacitor
Abstract Utilizing the dual functions of activated carbon (AC) both as a conductive agent and an active substance of a positive electrode, a hybrid supercapacitor (AC-MnO 2 &AC) with a composite of manganese dioxide (MnO 2 ) and activated carbon as the positive electrode (MnO 2 &AC) and AC as the negative electrode is fabricated, which integrates approximate symmetric and asymmetric behaviors in the distinct parts of 2 V operating windows. MnO 2 in the positive electrode and AC in the negative electrode together form a pure asymmetric structure, which extends the operating voltage to 2 V due to the compensatory effect of opposite over-potentials. In the range of 0–1.1 V, both AC in the positive and negative electrode assemble as a symmetric structure via a parallel connection which offers more capacitance and less internal resistance. The optimal mass proportions of electrodes are calculated though a mathematical process. In a stable operating window of 2 V, the capacitance of AC-MnO 2 &AC can reach 33.2 F g −1 . After 2500 cycles, maximum energy density is 18.2 Wh kg −1 with a 4% loss compared to the initial cycle. The power density is 10.1 kW kg −1 with an 8% loss.