Papers by Keyword: Hybrid Capacitor

Abstract: To improve the specific capacitance, power and energy of electrical energy storage devices, in particular hybrid capacitors, various methods of cathode material modification are used. One of the methods of modifying nanostructured materials without applying high temperatures, pressures and long reaction times is ultrasonic treatment. Although the interaction of ultrasound with the structure and surface of electrode materials is well enough studied, there are few works that investigate the optimal duration of ultrasonic treatment and its relationship with the capacitive characteristics of these materials. Therefore, we investigated the efficiency of ultrasonic dispersion of nanocrystalline nickel molybdate hydrate for 15, 60 and 90 minutes. The appearance of two cathodic peaks on cyclic voltammetry patterns was analyzed and the charge / discharge mechanism of the electrode based on nanocrystalline NiMoO₄ hydrate was presented. Based on the results of potentiodynamic and galvanostatic studies the specific capacitances of the initial NiMoO₄ and the material modified by ultrasound for 15, 60 and 90 minutes were calculated. The proton diffusion coefficients of nickel molybdate hydrate were determined on the basis of the Randles–Sevcik equation. NiMoO₄ subjected to ultrasonic dispersion for 60 min as a cathode material in a hybrid electrochemical system was tested.

Abstract: Composite electrode materials of amorphous FeOOH-based particles and carbon powder were prepared by heat treatment of composite powder obtained by hydrolyzing of mixed aqueous solutions of FeCl3 and Ti(SO4)2 into which electron conducting carbon powder was dispersed. They exhibited high capacities over 150 mAh g-1 and good cycle performance at large charge-discharge current density of 5 mA cm-2 (ca. 1 A g-1). In this case, the heat treatment was effective process to improve the cycle performance.

Abstract: Anatase-type TiO2-based oxide gel /carbon composites were treated chemically with LiOH aqueous solution at 60 °C. The crystalline phase of treated powder was examined by powder x-ray diffraction using CuKα radiation. The main diffraction peaks may be detected as belonging to cubic LiTiO2. High-rate lithium intercalation properties of the samples were estimated in nonaqueous electrolyte including lithium ions. The composite electrodes exhibited high coulombic efficiency over 90% at first cycle and high capacities over 200 mAh g-1 after 200 cycle at large charge-discharge current density of 5.0 mA cm-2 (3.7 A g-1). The composite materials are one of the promising candidates as electrode materials for energy storage devices, such as hybrid capacitor, that require high-power operations.

Abstract: In this study, mixed active material electrodes, composed of an activated carbon (MSP20) and LiCoO2, were prepared as cathodes for a high-capacitive hybrid capacitor. The electrochemical properties of (MSP20+LiCoO2)/Li cells were examined in terms of the weight composition and the particle size of LiCoO2 powder in the electrodes. As adding more LiCoO2 powders in the electrode, the volumetric capacity (mAh/ml) of the electrode became higher. In order to examine the size effect on the electrochemical performance, the LiCoO2 powders were modified by ball milling. The (MSP20+LiCoO2)/Li cells using 10 and 20 wt.% of 30h-milled LiCoO2 powder exhibited the lower internal resistivities and the better capacity retentions after 100 charge-discharge cycles than those using 10 or 20 wt.% of raw LiCoO2 powders.