Characterization Of Supercapacitors Research Articles

A Simple and Complete Supercapacitor Characterization System Using a Programmable Sourcemeter

The development of new materials and systems capable of storing energy efficiently with a fast power delivering has been the subject of several studies. Many techniques and instruments are used for the characterization of these systems. Some involve the use of electrochemical techniques, such as cyclic voltammetry and electrochemical impedance spectroscopy, while others use instruments specially developed for this purpose. In this study, we provide a simple and functional supercapacitor characterization system using a programmable sourcemeter with an embedded scripting language. For the validation of the system, commercial capacitors and supercapacitors devices based on activated carbon and manganese dioxide were used. In a few steps, the system is capable of efficiently determine the main parameters used in the characterization of supercapacitors, for instance, specific capacitance, specific energy density, specific power density and equivalent series resistance. From the data collected, the system can also determine the stability and performance of supercapacitors, which are fundamental parameters used in the development of new electrodes for energy storage devices. DOI: http://dx.doi.org/10.17807/orbital.v11i2.1374

Supercapacitors Characterization and Modeling Using Combined Electro-Thermal Stress Approach Batteries

This paper presents the supercapacitors (SC) behavior characterization using the temperature combined to the frequency of the dc-current ripples called here electro-thermal stress. To characterize the evolution of the resistance and the capacitance of the SC, the authors have evaluated the impact of the state of charge (SoC), the number of cycles, the temperature, and the temperature combined to the frequency of the dc-current ripples. This approach enables to show the variations of the SCs resistance and capacitance according to the real constraints imposed by application. The main contribution of this paper is focused on the SCs aging characterization and modeling, using the electro-thermal stress. The experimental tests of the SC characterization and modeling are based on the charge/discharge operations, using the fluctuating and no-fluctuating dc-current waveforms. The proposed model takes into account the variations of the resistance and capacitance of the SC according to the temperature, the frequency of dc-current ripples and the SoC. The terminal voltage of the SC obtained from the proposed model is close to the experimental result, with an error about 1%. So, the proposed model is satisfactory to predict the SCs behavior during the charge/discharge operations using a fluctuating dc-current combined to a variable temperature and SoC.

On The Inverse Relaxation Approach To Supercapacitors Characterization

A novel inverse relaxation technique for supercapacitor characterization is developed, modeled numerically, and experimentally tested on a number of commercial supercapacitors. It consists in shorting a supercapacitor for a short time τ, then switching to the open circuit regime and measuring an initial rebound and long–time relaxation. The results obtained are: the ratio of “easy” and “hard” to access capacitance and the dependence C(τ), that determines what the capacitance the system responds at time–scale τ; it can be viewed as an alternative to used by some manufacturers approach to characterize a supercapacitor by fixed capacitance and time–scale dependent internal resistance. Among the advantages of proposed technique is that it does not require a source of fixed current, what simplifies the setup and allows a high discharge current regime. The approach can be used as a replacement of low–frequency impedance measurements and the ones of IEC 62391 type, it can be effectively applied to characterization of supercapacitors and other relaxation type systems with porous internal structure. The technique can be completely automated by a microcontroller to measure, analyze, and output the results.

On the Impact of Mobility on Battery-Less RF Energy Harvesting System Performance.

The future of Internet of Things (IoT) envisions billions of sensors integrated with the physical environment. At the same time, recharging and replacing batteries on this infrastructure could result not only in high maintenance costs, but also large amounts of toxic waste due to the need to dispose of old batteries. Recently, battery-free sensor platforms have been developed that use supercapacitors as energy storage, promising maintenance-free and perpetual sensor operation. While prior work focused on supercapacitor characterization, modelling and supercapacitor-aware scheduling, the impact of mobility on capacitor charging and overall sensor application performance has been largely ignored. We show that supercapacitor size is critical for mobile system performance and that selecting an optimal value is not trivial: small capacitors charge quickly and enable the node to operate in low energy environments, but cannot support intensive tasks such as communication or reprogramming; increasing the capacitor size, on the other hand, enables the support for energy-intensive tasks, but may prevent the node from booting at all if the node navigates in a low energy area. The paper investigates this problem and proposes a hybrid storage solution that uses an adaptive learning algorithm to predict the amount of available ambient energy and dynamically switch between two capacitors depending on the environment. The evaluation based on extensive simulations and prototype measurements showed up to 40% and 80% improvement compared to a fixed-capacitor approach in terms of the amount of harvested energy and sensor coverage.

Solid-state supercapacitor application for pressure sensing

The aim of this work is to study pressure sensing effect of the developed flexible solid-state supercapacitor which uses conductive carbon black/polyisoprene composite electrode and PVA/H3PO4 electrolyte. Electrochemical characterization of supercapacitor has been performed to evaluate the performance of the supercapacitor as energy storage device and the gravimetric capacitance has been calculated to be 4.09 F g−1 (4.4 mA g−1). Further the pressure sensing effect has been investigated at various pressure values and during cyclic compression. Capacitance increase is found to be 818 ± 29 µF at pressure of 1 MPa. The increase is caused by higher interface area between electrode and electrolyte surface under uniaxial pressure. The results show that deformation of flexible solid-state supercapacitor can contribute to its performance and this type of device could be considered for use in energy harvesting systems.

Fabrication and electrochemical characterization of super-capacitor based on three-dimensional composite structure of graphene and a vertical array of carbon nanotubes

We have demonstrated a three-dimensional composite structure of graphene and carbon nanotubes as electrodes for super-capacitors. The goal of this study is to fabricate and test the vertically grown carbon nanotubes on the graphene layer acting as a spacer to avoid self-aggregation of the graphene layers while realizing high active surface area for high energy density, specific capacitance, and power density. A vertical array of carbon nanotubes on silicon substrates was grown by a low-pressure chemical vapor deposition process using anodized aluminum oxide nanoporous template fabricated on silicon substrates. Subsequently, a graphene layer was grown by another low-pressure chemical vapor deposition process on top of a vertical array of carbon nanotubes. The Raman spectra confirmed the successful growth of carbon nanotubes followed by the growth of high-quality graphene. The average measured capacitance of the three-dimensional composite structure of graphene-carbon nanotube was 780 µFcm−2 at 100 mVs−1.

Design and characterization of asymmetric supercapacitor useful in hybrid energy storage systems for electric vehicles

Energy storage systems (ESSs) of electric vehicles (EVs) require high energy density and high power density concurrently. The ESSs with only supercapacitors (SCs) or high performance batteries (hpBs) have egregious limitations, and are unable to meet up the demands for specific power and energy concurrently. This study reports on the design and characterization of asymmetric supercapacitor based on activated carbon (ACC) and MoS2 that suitable for use in hybrid energy storage systems in electric vehicles. The contribution of the double storage mechanism processes obtained from the faradaic storage sulfide material (MoS2) combined with the excellent electric double layer storage from the activated carbon led to the overall realization of an specific energy of ~ 27.82 Wh kg-1 with a related specific power of 1000 W kg-1 at a 0.5 A g-1 gravimetric current density. In addition, the device also exhibited a 100% coulombic efficiency even after cycling for 10,000 continuous charge-discharge cycles serving as the highest reported presently on this device type. This shows the unique potential of adopting such ACC/MoS2 materials as exceptional candidates to act as SC cells in the hybrid system for energy storage in electric vehicles.

Low temperature and cost-effective growth of vertically aligned carbon nanofibers using spin-coated polymer-stabilized palladium nanocatalysts

We describe a fast and cost-effective process for the growth of carbon nanofibers (CNFs) at a temperature compatible with complementary metal oxide semiconductor technology, using highly stable polymer–Pd nanohybrid colloidal solutions of palladium catalyst nanoparticles (NPs). Two polymer–Pd nanohybrids, namely poly(lauryl methacrylate)-block-poly((2-acetoacetoxy)ethyl methacrylate)/Pd (LauMAx-b-AEMAy/Pd) and polyvinylpyrrolidone/Pd were prepared in organic solvents and spin-coated onto silicon substrates. Subsequently, vertically aligned CNFs were grown on these NPs by plasma enhanced chemical vapor deposition at different temperatures. The electrical properties of the grown CNFs were evaluated using an electrochemical method, commonly used for the characterization of supercapacitors. The results show that the polymer–Pd nanohybrid solutions offer the optimum size range of palladium catalyst NPs enabling the growth of CNFs at temperatures as low as 350 °C. Furthermore, the CNFs grown at such a low temperature are vertically aligned similar to the CNFs grown at 550 °C. Finally the capacitive behavior of these CNFs was similar to that of the CNFs grown at high temperature assuring the same electrical properties thus enabling their usage in different applications such as on-chip capacitors, interconnects, thermal heat sink and energy storage solutions.

Interfacial Redox Phenomena for Enhanced Aqueous Supercapacitors

The paper reports on electrochemical characterization of several supercapacitors operating in aqueous electrolytes and discusses a strategy for enhancing their performance. Various electrolytes such as alkaline (6 mol L−1 KOH), acidic (1 mol L−1 H2SO4) and neutral (1 mol L−1 KI and 1 mol L−1 Na2S2O3) were investigated in terms of electrochemical stability and redox activity. A new concept of capacitor with two electrodes operating in different electrolytes is demonstrated. The positive electrode worked in KI solution whereas KOH solution served as an electrolytic medium for the negative electrode. As a result, improved capacitance values and energy density for a capacitor with a combined electrolyte have been obtained because of the beneficial redox phenomena on both electrodes.

Fabrication and characterization of solution-processed carbon nanotube supercapacitors

ABSTRACTWe report the fabrication and characterization of supercapacitors prepared on a flexible substrate using a printable, high-viscosity carbon nanotube (CNT) ink. The CNT-hemicellulose composite ink was prepared using ultrasonication and applied on the substrate with a doctor blade. Aqueous sodium chloride was used as electrolyte. The capacitance of the supercapacitors was 16 mF for a device size of 2 cm2. The measurements were carried out in accordance to an international standard for electric double layer capacitors.

Review of characterization methods for supercapacitor modelling

To manage an electrical network in a stationary application or in an embedded application such as hybrid or electrical vehicles, it is necessary to understand and to model the electrical behaviour of the sources on board. This paper deals with the characterization of supercapacitors as electrical power sources, in order to model them. Three equivalent electrical circuit models of supercapacitor are proposed, corresponding to different levels of modelling. The identification of these model parameters is carried out with adapted characterization tests, such as charge and discharge test at constant current and Electrochemical Impedance Spectroscopy in environmental constraints. The experimental results are compared and analysed, for many characterizations in different test conditions in terms of voltage (from 0.5 to 2.7 V), temperature (from −20 to 55 °C), frequency (from 50 mHz to 20 kHz) and on many supercapacitor cells of several capacitances (650 F, 1200 F and 3000 F) and from two suppliers (Maxwell and Batscap).

Electrochemical characterization of supercapacitors based on carbons derived from Sorona activated by ZnCl2

Carbons derived by the pyrolysis of Sorona activated by <TEX>$ZnCl_2$</TEX> in the ratio of 1:20 and non-porogen Sorona carbons are used as the electrode materials in asymmetric electrochemical supercapacitors and electrochemical behavior is investigated. Scanning electron microscopy (SEM) reveals the porogen free carbons show a flake-like structure and the <TEX>$ZnCl_2$</TEX>-treated Sorona carbons have a loose, disjoint structure without any particular shape. Cyclic voltammetric (CV) studies show specific prolate rectangular shape and gives good capacitive properties.

Characterization of commercial supercapacitors for low temperature applications

Electrochemical characterizations at low temperature and floating tests have been performed on 600F commercial supercapacitor (SC) for acetonitrile (AN)-based and AN + methyl acetate (MA) mixed electrolytes. From −40 to +20 °C, AN electrolyte showed slightly higher capacitance than those of AN + MA mixed electrolytes (25 and 33 vol.% of MA). At −55 °C, however, AN electrolyte did not cycle at all, while MA mixed electrolyte normally cycled with a slight decrease in their capacitance. From electrochemical impedance spectroscopy measurements, the whole resistance for AN-based cells at −55 °C was found to be about 10,000 times higher than that of +20 °C, while a 40-fold increase in the cell resistance was obtained for the MA mixture between 20 and −55 °C. From the results of floating tests at 2.7 V and 60 °C for 1 month, the 25 vol.% MA mixture showed no change and slight decreased but stable capacitance.

Nanoscale Characterization of CDC Supercapacitors by In Situ Scanning Probe Microscopy Methods

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Preparation and Electrochemical Characterization of Li-Ion Supercapacitor

A new type of Li-ion supercapacitor was fabracatied with activated carbon as cathode and graphite pre-intercalated Li ion as anode. The electrochemical characterization was also conducted with cyclic voltammetry and AC impedance methods. By this unique cell design , the capacitance of Li-ion supercapacitor keep the same level to double elecric layer supercapacitor ,But the voltage window of supercapacitor can be enhanced from 2.5V to 4.2V.So the energy density of Li-ion supercapacitor can be enhanced 4 times of common carbon-based supacapacitor. There is above 99% capacitance retention for Li ion supercapacitor after 200 cycles at 200mA discharge current. A pure capacitance behavior can be found at the frequency below the knee in its AC impedance spectroscopy.

Supercapacitor Characterization and Thermal Modelling With Reversible and Irreversible Heat Effect

This paper investigates double layer capacitor (or supercapacitor) thermal modelling. The originality of this work resides in the fact that 4 type K thermocouples are inserted inside a 350 F supercapacitor modified cell. These thermocouples allow supercapacitor internal temperature measurement. Experimental results have shown that the electrical storage device temperature increases in the phase of charge and decreases during the discharge. The developed model takes into account the effect which is due to the reversible heat generation in the supercapacitor. The model is based on heat equation solution and allows temperature distribution determination inside and outside the supercapacitor as a function of the position and of the time. The model is developed for double layer capacitor based on activated carbon and organic electrolyte technology.

Self-discharge analysis and characterization of supercapacitors for environmentally powered wireless sensor network applications

A new approach is presented to characterize the variable leakage resistance, a parameter in the variable leakage resistance model we developed to model supercapacitors used in environmentally powered wireless sensor network applications. Based on an analysis of the supercapacitor terminal behavior during the self-discharge, the variable leakage resistance is modeled as a function of the supercapacitor terminal voltage instead of the self-discharge time, which is more practical for an environmentally powered wireless sensor node. The new characterization approach is implemented and validated using MATLAB Simulink with a 10F supercapacitor as an example. In addition, effects of initial voltages and temperatures on the supercapacitor self-discharge rate and the variable leakage resistance value are explored.

Characterization of Non-Aqueous Supercapacitors Based on Titanium Carbide Derived Carbon Electrodes and Novel Doubly Charged Cation Based Salts

The electrochemical characteristics for the supercapacitors based on the titanium carbide derived carbon (CDC-TiC) electrodes in 0.4 M N,N-dimethyl-1,4-diazabicyclo[2,2,2]octanediium tetrafluoroborate (DMDABCO(BF4)2), 0.2 M DMDABCO(BF4)2 + 0.2 M triethylmethylammonium tetrafluoroborate (TEMABF4), and 0.4 M TEMABF4 in g-butyrolactone (g-BL) have been studied using cyclic voltammetry, constant current charging/discharging and electrochemical impedance spectroscopy. The ideal supercapacitor behaviour was observed in a wide region of cell voltages (U < 3.0 V) in 0.4 M DMDABCO(BF4)2 in g-BL. The geometry of solvation shell around DMDABCO2+ has been optimized with molecular dynamics calculations and the coordination number equal to 15, have been proposed and compared with electrochemical and gas sorption data for CDC-TiC. The gravimetric capacitance 129 F g-1, energy 40.6 W h kg-1 and power 93 kW kg-1 were established for the CDC-TiC electrodes in 0.4 M DMDABCO(BF4)2 g-BL solution.

Modeling and characterization of supercapacitors for wireless sensor network applications

A simple circuit model is developed to describe supercapacitor behavior, which uses two resistor–capacitor branches with different time constants to characterize the charging and redistribution processes, and a variable leakage resistance to characterize the self-discharge process. The parameter values of a supercapacitor can be determined by a charging-redistribution experiment and a self-discharge experiment. The modeling and characterization procedures are illustrated using a 22F supercapacitor. The accuracy of the model is compared with that of other models often used in power electronics applications. The results show that the proposed model has better accuracy in characterizing the self-discharge process while maintaining similar performance as other models during charging and redistribution processes. Additionally, the proposed model is evaluated in a simplified energy storage system for self-powered wireless sensors. The model performance is compared with that of a commonly used energy recursive equation (ERE) model. The results demonstrate that the proposed model can predict the evolution profile of voltage across the supercapacitor more accurately than the ERE model, and therefore provides a better alternative for supporting research on storage system design and power management for wireless sensor networks.

Characterization of graphene-based supercapacitors fabricated on Al foils using Au or Pd thin films as interlayers

We demonstrate that an Au or Pd interlayer between graphene and an Al-foil current collector plays an important role in enhancing supercapacitor performance. Graphene was prepared by scalable chemical exfoliation and mild thermal reduction (∼150 °C) processes. Working electrodes were prepared by coating the graphene on Au/Al or Pd/Al by drop-dry method. The graphene deposited on the noble metals Au and Pd demonstrated excellent supercapacitor performance. Estimated specific energy and specific power of supercapacitors were ∼40 Wh/kg and ∼40 kW/kg at the current density of ∼33 A/g, when operated in organic solution. Altogether, we demonstrate that employing noble metals in the fabrication of graphene-based supercapacitors can lead to excellent performance, and this could be a critical basis for further development of graphene-based supercapacitors.