Chemical Capacitors Research Articles

Retraction Note: Graphene-Based Important Carbon Structures and Nanomaterials for Energy Storage Applications as Chemical Capacitors and Supercapacitor Electrodes: a Review

Retraction Note: Graphene-Based Important Carbon Structures and Nanomaterials for Energy Storage Applications as Chemical Capacitors and Supercapacitor Electrodes: a Review

RETRACTED ARTICLE: Graphene-Based Important Carbon Structures and Nanomaterials for Energy Storage Applications as Chemical Capacitors and Supercapacitor Electrodes: a Review

RETRACTED ARTICLE: Graphene-Based Important Carbon Structures and Nanomaterials for Energy Storage Applications as Chemical Capacitors and Supercapacitor Electrodes: a Review

(Digital Presentation) Vanadium Intercalated Cobalt Trimesic MOF Composite for Enhanced Solid-State Asymmetric Supercapacitor Storage

Metal organic framework (MOF) is a supramolecular coordination material composed of metal ions coordination, nodes, and organic ligands. MOFs were used as active materials for chemical capacitors to realize the high electrochemical performance, providing adequate redox sites and accelerating ion diffusion rate. Using MOF as a template to fabricate a novel platform can deliver large specific surface areas and abundant oxidation-active sites to augment electrical conductivity. The electrode material based on a MOF has a unique morphology that can significantly shorten charge transport paths to alleviate the electron transport and diffusion, thus strengthening the catalytic performance of the electrode materials. Also, the incorporation of vanadium in the intermediate leads to a broad impact on the morphology and the electrochemical energy storage of Cobalt-Trimesic matrix worked as a base for fabricating the composite. The DMF is a solvent to prepare the vanadium cobalt oxide composite derived using the MOF matrix. Trimesic acid is used as an initial organic linker precursor to initiate the formation of MOF of cobalt in DMF solvent. Then the vanadium ion is integrated into the same material matrix. In this study, the impact of organic system precursors and the integration of annealing play a pivotal role in alleviating the enhanced electrochemical storage response. After analyzing through XRD, the corresponding MOF crystal peaks are prominently affirmed. The high intensified peaks in the obtained patterns symbolize the oxide phase of cobalt vanadium and confirm the formation derived from MOF. The FTIR spectroscopy investigation depicted the proper presence of cobalt, vanadium, carbon, and nitrogen. The observed FESEM morphology illustrated the dissimilar structure and involved in the charge storage likewise. The morphology significantly impacts surface-dependent charge storage with having porosity introduced. High-temperature annealing also consists of the crystal orientation of the bi-metallic MOF matrix and creates porosity on the effective surface area.The Co-MOF-V oxide composite is thoroughly investigated individually in three-electrode arrangements for analyzing the electrochemical charge storage in 2MKOH represented in Fig.1 (c-d). Firstly, the oxide is scrutinized as working positive electrodes and measured in the potential window of -0.2 to 0.6 V w.r.t the saturated calomel reference electrode. The accomplished specific capacitance value from the cyclic voltammetry plot is 549 F/g at 2mV/s scan rate. Furthermore, the charge-discharge analysis of the composite delineated an admirable discharge time at 3mA/cm2 current density. It portrayed 349 F/g specific capacitance, leading to higher specific energy and specific power of 31.02Wh/kg and 159.53W/kg at the value of the same current density. The Nyquist plot corroborates that the electrode resistance, electrode-electrolyte interfacing resistance, and the value of diffuse layer resistance are significantly less. This study can bestow a greater pathway of ion transportation from the electrolyte to active electrode material that abetted to conversate superior storage using complete morphology. The transition metal possesses a variational oxidation state that directly contributes to this MOF composite's pseudocapacitive charge storage process. Alternatively, comparable analysis is directed over anode material that is lignocellulose derived activated porous carbon. It is depicted in Fig.1(e-f) in the potential window of -1 to 0v w.r.t the Ag/AgCl electrode in 2M KOH. The gained specific capacitance from the cyclic voltammetry analysis is 426 F/g at a 2mV/s scan rate. Besides, the charge-discharge study of the same carbon depicted admirable discharge time at 0.5A/g current density and portrayed 565 F/g specific capacitance. The specific energy and power of 78.47Wh/kg and 282W/kg at the same current density. Also, the integrated porous system with the high active surface area, which significantly comes from the MOF matrix, provides an added phase to strengthen the amount of storage like EDLC formation.Furthermore, combining both of those active materials, the asymmetric supercapacitor storage is made up [Fig.1 (g-h)]. That system works upon 0 to 1.4V windows. The attained areal capacitance is 0.54 F/cm2, and volumetric capacitance is 0.68 F/cm3 in the current density of 4mA/cm2. The Ragone plot shows its perfect positioning in the region of asymmetric storage. This ASC system delineated coulombic efficiency 79% of capacitive retention 75% after the 10,000 long cycle stability study. From the electrochemical impedance spectroscopy analysis, the obtained interfacing and electrode resistance diffuse layer resistance is found significantly lesser and upwards. Figure 1

Molecular dynamics investigation of charging process in polyelectrolyte-based supercapacitors

Supercapacitors are one of the technologically impressive types of energy storage devices that are supposed to fill the gap between chemical batteries and dielectric capacitors in terms of power and energy density. Many kinds of materials have been investigated to be used as supercapacitors’ electrolytes to overcome the known limitations of them. The properties of polymer-based electrolytes show a promising way to defeat some of these limitations. In this paper, a simplified model of polymer-based electrolytes between two electrodes is numerically investigated using the Molecular Dynamics simulation. The simulations are conducted for three different Bjerrum lengths and a typical range of applied voltages. The results showed a higher differential capacitance compared to the cases using ionic-liquid electrolytes. Our investigations indicate a rich domain in molecular behaviors of polymer-based electrolytes that should be considered in future supercapacitors.

Electrochemical Circuit Elements.

The vast majority of electrochemical processes can be modelled by resistors and capacitors. These will then be, in addition to usual circuit elements, electrochemical and chemical resistors or chemical capacitors. The paper shows the significance of understanding these parameters and their connections in given systems for a variety of timely scientific examples. This rationale mirrors one of the intellectual facets, if not the most important one, of Janko Jamnik's scientific work.

Chemical Capacitors and Quaternary Ammonium Salts

A capacitor is an electrical device that can store energy in an electric field between a pair of closely spaced conductors. Its application as an energy storage device —an alternative to rechargeable batteries— has been receiving considerable attention. There are chemical capacitors using liquid electrolytes such as aluminum electrolytic capacitors and double-layer capacitors, and they utilize quaternary ammonium salts in their nonaqueous electrolytes. After a brief explanation of the working principles of these chemical capacitors and their requirements for electrolytes, the practical applications of quaternary ammonium salts for aluminum electrolytic capacitors and double-layer capacitors are reviewed from the historical and technological viewpoints based on research conducted in our laboratory.

新ゲートパターンアクティブ補助共振スナバソフトスイッチングインバータの検討

This paper presents a new topology of the voltage source type bridge soft switching inverter circuit which proposes a novel active edge resonant snubber circuits using the auxiliary power switches. This advanced inverter is more suitable and acceptable for an uninterruptible power supply, such as PFC power converter, utility-interactive bi-directional power converter and new energy related distributed power supplies. The soft switching operation principle and design procedure of the active auxiliary edge resonant snubber circuit are described and discussed for the high power applications. Both the main active power switches and the auxiliary power switches achieve ZVS or ZCS for sinewave PWM inverter. This inverter does not need any sensor interfaced circuit to detect the voltage or the current and does not also required for the electrolytic chemical capacitors to make the neutral point of the DC power supply voltage side. This paper proposes a new gate timing pattern of switches in this soft switching inverter circuit, too. This method can limit the current of the active edge resonant snubber circuits lower than a level of the load current. As a result, the total efficiency characteristics of the converter system is improved high in all load range.

Impedance spectroscopy of mixed conductors with semi-blocking boundaries

Using generalised circuits consisting of three basic elements (electrochemical resistors, electrical and chemical capacitors), the small signal response of mixed conductors is considered. Simple approximate circuits for polycrystals with grain boundaries that act as obstacles for ions, electrons or both are derived. It is shown that Warburg-type impedance can be induced also by grain boundaries, not only by electrodes. As shown exemplarily, such models are appropriate also for analysis of impedance spectra obtained in studies of mixed conductive cathodes in Li-batteries.

Novel poly(vinyl alcohol)–KOH–H 2O alkaline polymer electrolyte

A series of alkaline thin-film solid electrolytes, based on poly(vinyl alcohol) (PVA), potassium hydroxide (KOH) and water (PVA–KOH–H 2O) were prepared. Their conductivity was studied using complex impedance method. The most conducting foils were composed of ca. 40 wt.% of PVA, 25–30 wt.% of KOH, and 30–35 wt.% of water. Typical conductivity of such foils reached the level of nearly 10 −3 Ω −1 cm −1 at room temperature. Temperature dependence of the conductivity was found to be in agreement with the Arrhenius expression with the activation energy of the order of 28–22 kJ mol −1, depending on the electrolytes composition. The electrochemical stability window at the metal/electrolyte interface is of 1.5 V for stainless steel and nickel, and of 1.7 and 2.75 V for platinum and gold, respectively. Such alkaline electrolytes are interesting from the point of view of their potential application in all-solid rechargeable alkaline batteries as well as in small electrochemical devices, such as chemical capacitors, electrochromic or photogalvanic devices.

Electrokinetic phenomena in fine-porous diaphragms at open chemical circuits

Classical electrokinetic phenomena are considered a coupling between electrical and hydraulic circuits where the diaphragm plays the role of an electromotive or a volumomotive force. Particular electrokinetic phenomena correspond to limiting conditions in those two circuits. Similarly, for fine porous diaphragms, equivalent chemical circuits are introduced to account for concentrational polarization. Classical electrokinetic phenomena turn out to be a particular mode occurring at closed chemical circuits. A new class of electrokinetic phenomena occurring at open chemical circuits is introduced. The examples of filtration potential and electro-osmotic pressure at charged chemical capacitors are considered in detail. The experimental conditions of observing the new phenomena and their advantages in terms of unambiguous interpretation of experimental data are then discussed.

Effect of nuclear radiation on the electrical properties of chemical double layer capacitors

The effects of nuclear radiation on the electrical properties of chemical double-layer capacitors are determined. The capacitors were irradiated in a 2-MW nuclear reactor to different fluence levels. The exposure rate was 2.2*10/sup 10/ n/cm/sup 2/-s for thermal neutrons, 9.52*10/sup 8/ n/cm/sup 2/-s for fast neutrons (>3 MeV), and 1.47*10/sup 6/ rad/h for gamma radiation. The properties measured during and after irradiation included the capacitance, equivalent series resistance, and open-circuit voltage. The postirradiation effect on the leakage current was also determined. It was found that, while the capacitance increased during irradiation, the equivalent series resistance and the open-circuit voltage decreased slightly during irradiation. Changes in these properties, however, were not permanent, as was evident from postirradiation measurements. The leakage current did not show any significant change with radiation. The results indicate that chemical double-layer capacitors can be suitably used as a backup power source in electronic equipment operating in a radiation environment with total fluences up to 4.05*10/sup 14/ n/cm/sup 2/. >