Performance Of Ultracapacitors Research Articles

Effect of electrolytes on the performance of graphene oxide anode material for ultracapacitor, Li-ion capacitor, and Li-ion battery: three-in-one approach

Graphene-based 2D nanomaterials are gaining much interest in energy storage systems, specifically in ultracapacitors. Various electrolytes increase the performance of ultracapacitor (UC), Li-Ion capacitor (LIC), and Li-Ion battery (LIB). In the present work, we have successfully designed a "three-in-one" artificial method to engineer anode from a single precursor for high-performance UC, LIC, and LIB. In the present investigation, graphene oxide (GO) slurry was developed using the modified Hummers’ method. The effect of KOH, H2SO4, and KCl electrolytes on electrochemical performance of UC was demonstrated. The LiPF6 organic electrolyte solution on electrochemical performance of LIC and LIB is demonstrated. The GO deposited on stainless steel electrode achieved its highest specific capacitance of 422 F/g, energy density of 45.50 kWh/kg, and power density of 10,000 W/kg in 3.0 M in KCl, whereas GO as an anode material delivered a first discharge capacity of 456 mAh/g at 0.05 A/g current density with the efficiency of 100%.

Preparation and characterization of activated carbon derived from the bovine bone doped urea as an electrode material

Activated carbon was prepared as an electrode by utilizing available bovine bone waste. This material is an alternative to graphene, which still has a high price value. The aims of this study were to characterize and analyze the effect of urea on the manufacture of activated carbon as an electrode, and to analyze the performance of ultracapacitors from modified electrodes combined with several electrolytes. Urea is formulated because it has a nitrogen group in the activated carbon synthesis process. Treatment of bovine bone carbon started from size reduction and carbonization, activation with KOH. While the carbon modification process added urea (1:1, 1:2, 1:3) and continued with washing and neutralization. Activated carbon powder has hydroxyapatite, CaO, and CaOH, which maintains its macroscopic structure during combustion. On the carbon surface there are active groups such as hydroxyl, amine derivatives, phosphates. Carbon with a large surface area has nanometer-sized porosity and pore volume so that it can be used to provide space for energy storage. The results showed that the carbon added with urea (1:2) had the best characterization. The performance of the ultracapacitor was measured by its capacitance of 292 F/g and 0.1 A/g in the organic electrolyte liquid TEABF4.

Process-Based Statistical Modeling for Ball Mill Machine to Improve Performance of Nylon Ultracapacitor

The generation of electrical energy from renewable energy sources is rapidly increasing across the world due to its many advantages. Renewable energy source is also known as clean energy source. The energy storage devices are playing an important role in both renewable generation and distribution of power. The energy storing devices also helps to improve stability of electrical power grid. The electrode, electrolyte and separators are the main components of ultracapacitors. The performance of ultracapacitors mainly depends on the properties of electrode material, the type of separator used, properties of electrolyte used and its concentration level. Nylon as a separator material for ultracapacitors is investigated. Various parameters of nylon-based ultracapacitors are compared with conventional polyethylene-based ultracapacitors. Very less research work has been done on the processing of electrode material. Ball milling is the most commonly used material processing method in energy storage devices such as ultracapacitors, battery and fuel cells. The effect of ball milling parameters on the performance of ultracapacitors needs to be investigated. Most significant factors of ball milling parameters of electrode material for ultracapacitor are identified. Modeling of ball milling process on electrode material is done by using the statistical method- design of the experiment. The novel ball mill machine with some unique features is also presented. Pulse current density is taken as new output parameters which is more important than an internal resistance and specific capacitance. Most significant ball mill machine parameters are taken as input parameters and specific capacitance, internal resistance along with pulse current density are taken as output parameters for the modeling of nylon-based ultracapacitors.

Research on dynamic optimal control strategy of distributed super capacitor energy storage system based on convolution neural network

SummaryCompared with other modes of transport, urban rail transit has significant advantages such as large capacity, punctual safety, energy saving, and environmental protection. For pure electric buses, the problem of slow start, large battery energy loss, short battery life, and insufficient recovery of braking energy is caused by the use of single energy only. The power battery and super capacitor are combined to form a compound power supply to solve the problem. In order to improve the feature extraction ability of convolution neural networks, a deep convolution neural network model based on continuous convolution is designed. The model uses small scale convolution kernel to extract local features more carefully, and increases the nonlinear expression ability of the model by means of two continuous coiling layers. Dropout technology is used to reduce the interdependence between neurons, and the model is optimized by suppressing network overfitting. If the battery and the supercapacitor are combined to form a dual energy source system, it can not only meet the instantaneous high power demand of the electric vehicle but also prolong the life of the battery. Increasing the mileage of electric vehicles has become the development direction of pure electric vehicles. Due to its fast charging and discharging speed, long cycle life, and friendly environment, supercapacitor has unique advantages and development prospects in solving the problem of urban rail transit regeneration failure, performance analysis, modeling, and parameter identification of ultracapacitor. The performance of ultracapacitor is analyzed, and an improved dynamic equivalent circuit model of ultracapacitor is established. Therefore, this paper studies the control strategy of dual energy source storage system and the driving range of the dual energy source pure electric vehicle, which has a broad application prospect and practical significance.

Enhanced performance of ultracapacitors using redox additive-based electrolytes

Different concentrations of potassium iodide (KI) as redox additive had been added to 1 M sulfuric acid (H2SO4) electrolyte with an aim of enhancing the capacitance and energy density of ultracapacitors via redox reactions at the interfaces of electrode–electrolyte. Ultracapacitors were fabricated using chemically treated activated carbon as electrode with H2SO4 and H2SO4–KI as an electrolyte. The electrochemical performances of fabricated supercapacitors were investigated by impedance spectroscopy, cyclic voltammetry and charge–discharge techniques. The maximum capacitance ‘C’ was observed with redox additives-based electrolyte system comprising 1 M H2SO4–0.3 M KI (1072 F g− 1), which is very much higher than conventional 1 M H2SO4 (61.3 F g− 1) aqueous electrolyte-based ultracapacitors. It corresponds to an energy density of 20.49 Wh kg− 1 at 2.1 A g− 1 for redox additive-based electrolyte, which is six times higher as compared to that of pristine electrolyte (1 M H2SO4) having energy density of only 3.36 Wh kg− 1. The temperature dependence behavior of fabricated cell was also analyzed, which shows increasing pattern in its capacitance values in a temperature range of 5–70 °C. Under cyclic stability test, redox electrolyte-based system shows almost 100% capacitance retention up to 5000 cycles and even more. For comparison, ultracapacitors based on polymer gel electrolyte polyvinyl alcohol (PVA) (10 wt%)—{H2SO4 (1 M)–KI (0.3 M)} (90 wt%) have been fabricated and characterized with the same electrode materials.

Scalable holey graphene synthesis and dense electrode fabrication toward high-performance ultracapacitors.

Graphene has attracted a lot of attention for ultracapacitor electrodes because of its high electrical conductivity, high surface area, and superb chemical stability. However, poor volumetric capacitive performance of typical graphene-based electrodes has hindered their practical applications because of the extremely low density. Herein we report a scalable synthesis method of holey graphene (h-Graphene) in a single step without using any catalysts or special chemicals. The film made of the as-synthesized h-Graphene exhibited relatively strong mechanical strength, 2D hole morphology, high density, and facile processability. This scalable one-step synthesis method for h-Graphene is time-efficient, cost-efficient, environmentally friendly, and generally applicable to other two-dimensional materials. The ultracapacitor electrodes based on the h-Graphene show a remarkably improved volumetric capacitance with about 700% increase compared to that of regular graphene electrodes. Modeling on individual h-Graphene was carried out to understand the excellent processability and improved ultracapacitor performance.

Combustion synthesis of graphene and ultracapacitor performance

Graphene sheets are synthesized by a simple method starting from graphitic oxide as a precursor. Reaction of graphitic oxide at 250 °C with a combustion mixture of urea and ammonium nitrate results in the formation of thin graphene sheets. Graphene formation is characterized by XRD, TGA, XPS and TEM. Graphene materials synthesized by this method are investigated as an ultracapacitor material. Specific capacitance values of about 70 F/g are obtained at a current density of 100 mA/g by using KOH as an electrolyte.

Design of a soft switching bidirectional DC-DC power converter for ultracapacitor-battery interfaces

One solution to the low specific power of hybrid electric vehicular batteries is a hybrid energy storage system (HESS) that takes advantage of the high specific power performance of ultra-capacitors. The design of a type of zero current transition (ZCT) soft switching bidirectional direct current-direct current (DC-DC) power converter that can be used as an ultra-capacitor-battery interface in an active parallel schema of a HESS is described. The circuit operation of the ZCT DC-DC power converter is depicted in detail. The HESS controller is designed as a two-layered hierarchical control structure: the first layer is responsible for working mode control of the HESS, and the second layer is responsible for DC-DC power converter control in which a fuzzy logic PID algorithmis employed. Simulation results indicate that this design is a potential solution to the problem of the low specific power of batteries, especially for regenerative braking and electric motor assist. The proposed active parallel schema with ZCT exhibits a significant advantage in power and energy decoupling. HESS with ZCT achieves better efficiency compared to the battery only operation. The experimental results validates the idea that the ultra-capacitor cooperates with the battery in acceleration mode.

Graphene oxide based conductive glue as a binder for ultracapacitor electrodes

An adhesive and conductive glue was created by synergistic assembly of graphene oxide (GO), single walled carbon nanotubes (SWCNTs) and conjugate polymer PEDOT:PSS in aqueous solution. The GO–SWCNTs–PEDOT:PSS glue can be used as a binder to fabricate metal oxide nanoparticle based ultracapacitors. Since the functional nanoparticles are immersed in this conductive gel, uniform electrical and mechanical interconnect can be achieved, leading to enhanced performance of ultracapacitors.

Ultracapacitor Performance of Reduced Graphene Oxide - Silica Composite

Graphene's unique properties show great promise for ultracapacitor applications. However, increasing the surface area available to electrolyte to increase the specific capacitance remains a challenge. In this paper we report on a method to synthesize a reduced graphene oxide-silica nanoparticle composite followed by etching with hydrofluoric acid. The composite and the etched samples were characterized using scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Nitrogen adsorption and capacitance measurements indicated an increase in the specific surface area and the specific capacitance in the post-etched samples suggesting that the silica nanoparticles act as a sacrificial jamming agent.

Design and Simulation of FC Plug-in Hybrid Bus with Ultracapacitors

The plug-in hybrid vehicle has been taken as one of the main streams of electric vehicles world wide with the development of battery technology and the remaining obstacles by the fuel cell to be broken through. Fuel cell plug-in vehicle will follow the engine plug-in vehicle because of the more and more strict control of green house gas emission. At this moment, lithium battery is still expensive and safety problem remains. The performance of ultra capacitor has been significantly improved and the price goes down rapidly because of being used on harbor vehicle and mechanical facilities such like container/cargo cranes in-small-batch. It has become a popular ESS for energy regeneration such like the transit buses. The paper will present the advantage and the performance of a FC plug-in hybrid transit bus with ultracapacitors and NiMH batteries. The design and simulation will be covered in the paper.