Equivalent Series Resistance Value Research Articles

Challenges in Measurement of Low-Value ESL and ESR of High-Performance PFN Capacitors for Klystron Modulator

In the high voltage line type pulse modulators, Pulse Forming Network (PFN) capacitors are one of the important components. These capacitors operate at peak kilo ampere current range and at repetition rate in the range of a few hundred hertz. The performance of these capacitors is critical w.r.t. overall system performance, and they are required to operate at high power density and low losses with high reliability. The Equivalent Series Inductance (ESL) and Equivalent Series Resistance (ESR) are two critical parameters that affect the performance of these capacitors. PFN modulator demands a capacitor of very low ESL and ESR for reliable operation and generation of high-voltage pulses. Higher ESR value adversely affects the performance of the capacitor by raising its temperature and thus deteriorating its life. ESL value does not directly affect life, but it affects the quality of high voltage pulse. In RRCAT, the PFN capacitors purchased from Indian manufacturers were showing high-temperature rise and failures. Therefore, new capacitors were designed to have lower ESL and ESR values. Measurement of ESL and ESR is important to evaluate the performance of the capacitors. The low value of these parameters makes their measurement a challenging task and requires special techniques. For low values of ESL and ESR (less than 100 mΩ) measurement, a differential measurement technique was used in which modification and different layouts were explored to improve the repetitive accuracy of the measurements. The differential ESR and ESL measurement techniques with more emphasis on the low-value ESR measurement will be discussed in the paper.

Intriguing and Facile Preparation Approach of CdO Nanorod-Based Abundant Chitosan for Symmetric Supercapacitors.

Abundant chitosan was rationally used for the green fabrication of cadmium oxide nanorods (CdO nanorods) owing to its environmentally benign characteristics, bioavailability, low cost, etc. However, the primary unsubstituted amino group of chitosan interacts with the surface of Cd salt at higher temperatures, resulting in CdO nanorod formation. A one-step hydrothermal technique was adopted in the presence of chitosan. Optical, structural, and morphology techniques characterized CdO nanorods. According to X-ray diffraction crystallography, CdO is well crystallized in the face-centered cubic lattice with an Fm-3m (225) space group. The AC@CdO nanoelectrode demonstrated an outstanding gravimetric capacitance of 320 F g-1 at a current density of 0.5 A g-1, nearly three-fold that of ordinary AC electrodes. The AC electrode and the AC@CdO nanoelectrode retain 90 and 93% of their initial specific capacitance after 10,000 galvanostatic charge discharge cycles. The AC@CdO nanoelectrode has a lower equivalent series resistance value than the AC electrode. Moreover, AC@CdO symmetric supercapacitor devices achieve excellent results in terms of specific energy, specific power, and capacitance retention.

Capacitor Condition Monitoring Method for Low-Capacitance StatComs: An Online Approach Using the Inherent Second-Harmonic Oscillations

The cascaded H-bridge low-capacitance static compensator (LC-StatCom) deliberately reduces the capacitor size while allowing large oscillations in capacitor voltages. When a capacitor deteriorates, its capacitance decreases or/and its equivalent series resistance (ESR) increases, compromising StatCom performance and safety. For this reason, the condition monitoring of the capacitors is important to schedule maintenance before failure. This letter introduces a cost-effective and nonintrusive method to monitor the condition of capacitors online. The proposed method offers real-time monitoring without requiring additional hardware or signal injection. The method uses averaged low-frequency signals instead of instantaneous high-frequency signals that can be corrupted by undesired high-frequency noise. Specifically, the method takes advantage of the inherent twice-fundamental-frequency oscillations on the capacitor voltage and current to identify the ESR and capacitance values. The method takes into account the influence of antialiasing filters required for sampling process. The letter shows experimental results that validate the fast and accurate performance of the proposed capacitor condition monitoring.

In-situ fabricated copper-holmium co-doped cobalt ferrite nanocomposite with cross-linked graphene as novel electrode material for supercapacitor application

Recently, hybrid electrode materials based on cross-linked carbon analogues have gained significant consideration for their excellent cyclic stability and high specific capacities. This work presents the fabrication of copper and holmium co-doped cobalt ferrite with cross-linked graphene (denoted as CH-CoF/CLG) through one-step hydrothermal route, as novel electrode material for supercapacitor study. The electrochemical performance of CH-CoF/CLG along with its counterparts i.e., CoF, CH-CoF was evaluated through CV, GCD, and EIS analysis using three electrode system. The specific capacitance (Csp) of CoF, CH-CoF, and CH-CoF/CLG nanocomposite at a sweep rate of 5 mV/s is 458 F/g, 762 F/g, and 1258 F/g, respectively, within a potential range of 0.0 to 0.6 V. For CH-CoF/CLG, the calculated slope value (b = 0.84) using power law showed that the energy storage mechanism is based on both capacitive and diffusional processes. The GCD test showed that CH-CoF/CLG exhibited long discharge time (td = 615 s), as compared to CH-CoF (td = 409 s), and CoF (td = 264 s). Moreover, after the fabrication of CH-CoF with CLG, the value of equivalent series resistance (ESR) and charge transfer resistance (Rct) for CH-CoF/CLG were decreased to 0.74 Ω and 0.84 Ω, compared to CoF (1.18 Ω and 1.29 Ω) and CH-CoF (0.88 Ω and 1.0 Ω). When tested for cyclic stability, CH-CoF/CLG displayed insignificant loss in performance up to 3000 cyclic runs. The high supercapacitor performance of CH-CoF/CLG can be assigned to the combined effects arising from the co-doping of transition metal and rare earth metal ions (Cu+2 and Ho+3) into CoF lattice, porous cross-linked structure, high wettability, low intrinsic resistance, and easy accessibility of KOH ions into deep layers of active material. As obtained results deduce that the CH-CoF/CLG nanocomposite is a competent capacitive material for energy storage.

Highly porous activated carbon prepared from the bio-waste of yellow mustard seed for high-capacity supercapacitor applications

Herein, we report the synthesis and electrochemical performance of the porous carbon produced from the bio-waste of the yellow mustard seed plant by the chemical activation process. We have optimized the chemical process to produce mesoporous activated carbon structure with a high specific surface area of 563 m2/g. The N2-sorption analysis confirms the presence of mesoporous structure of the activated carbon. The nanometer scale porosity and chemical composition of the activated carbon was investigated by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The crystallinity and defects analyses were conducted using XRD and Raman spectroscopy, revealing the existence of both amorphous and crystalline phases of the porous activated carbon. The electrochemical double-layered capacitor (EDLC) of the activated carbon electrodes was monitored for long-cycling. The galvanostatic charge-discharge (GCD) studies reveal a significantly high-specific capacity of 198 F/g at a current density of 0.25 A/g. In addition, the cyclic voltammetry (CV) measurements deliver a high reversible capacitive behavior and cyclic stability up to 2100 cycles. Furthermore, we observed a low value of equivalent series resistance (ESR) and charge transfer resistance, indicating an excellent electrode/electrolyte interface which can reversibly facilitate the electrolyte ion transport across the electrodes.

Development of Mesoporous Carbon Composites with Waste Plastics Derived Graphene and MnO2 for Supercapacitor Applications

This study demonstrates the influence of incorporating the composites such as waste plastics derived graphene (WPDG) and manganese dioxide (MnO2) in the mesoporous carbon (CR) and their consequent characteristics. The CR having WPDG as composite is named as CRG and MnO2 containing CR composite is termed as CRM. CRG possess the surface area as high as 790 m2g−1 along with pore volume of 0.565 cc g−1 and radius of 3.82 nm. Cyclic voltammetry (CV) study suggested that CR and CRG showed non-Faradic capacitive behavior with almost rectangular shaped CV profiles at low scan rates and this shows the existence of electric double layer structure. On the other hand, pseudo-capacitance is observed for CRM. Galvanostatic charge/discharge investigation revealed that the specific capacitance can be enhanced by 6 times upon subsequent immobilization of WPDG in CR whereas 4-fold upgrading in the specific capacitance after treating CR with MnO2. Interestingly, CRM showed higher capacitance retention as compared to CRG and is attributed to its smaller value of equivalent series resistance as compared to CRG. Ragone plots shown that the higher energy and power densities are found for the case of CRG.

Performance Improvement by Sampling Position Approach in Dual Loop Digital ACM Controlled DC-DC Boost Converter

In DC-DC boost converter mostly discontinuous voltage ripple is associated with Equivalent Series Resistance (ESR) of the output side capacitor. This voltage ripple makes the design of digital controllers challenging in deciding the appropriate sampling position in one switching period. The necessity of Right Half Plane Zero (RHPZ) elimination, which impacts the stability is managed by shifting the sampling position to OFF-time duration. This is mostly analyzed in the frequency domain. The proposed work provides the time-domain analysis in consideration of ESR impacting the RHPZ. A dual loop Digital Average Current Mode (DACM) controller which has two sampling position freedom is considered in this brief. The ESR value of the output capacitor for extracting the benefits of RHPZ elimination is proposed with help of the discrete-time modeling technique. An analytical discussion about the influence of RHPZ elimination with time-domain characteristics such as, voltage deviation, peak-to-peak inductor current oscillations, and efficiency is presented. Finally, two 60W boost converters prototype with different output capacitor (C) and its ESR <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(r_{C})$ </tex-math></inline-formula> values are developed to validate the proposed analysis.

Widening the limit of capacitance at high frequency for AC line-filtering applications using aqueous carbon-based supercapacitors

Portable electronic devices require high-performance miniaturised electronic components, preferably produced at low cost. In most line-powered applications, alternating current (AC) line filters are used to filter AC lines to direct current (DC) signals, making filtering capacitors a key necessity in modern electronic devices. Currently, aluminium electrolytic capacitors (AECs) are commonly used, which are bulky and have narrow electrochemical performance. Thus, replacing AECs with a compact capacitor design is highly desirable for future portable electronic devices but simultaneously very demanding. Here, we report the fabrication of an electrochemical capacitor with an electrode based on vertically aligned carbon nanostructures produced by a green plasma-enabled deposition technique. These capacitors delivered a high capacity of 1145 μF with a phase angle close to −80° at 100 Hz in a lab-scale two-electrode set-up. A prismatic prototype capacitor fabricated by stacking 10 pairs of electrodes (2.5 × 3.5 cm2) showed one of the lowest equivalent series resistance values, about 5.8 mΩ, with a high capacitance of ∼12 mF at 100 Hz. This performance delivered at the lab scale and in industrial-relevant environments suggests such electrochemical capacitors represent a suitable alternative to conventional AECs for high-frequency filtering applications.

Influence of fuel to oxidizer ratio on the supercapacitive properties of NiO synthesized by solution combustion method

Porous Nickel oxide nanocrystallites were successfully synthesized by a facile single-step glycine assisted solution combustion method without a post calcination treatment. Effect of fuel to oxidizer (F/O) ratio on the combustion behaviour, crystallite size, surface characteristics, morphology, and agglomeration were thoroughly investigated. A systematic variation of crystallite size with F/O ratio was revealed from PXRD studies. BET studies showed a decrease of surface area with increase of F/O ratio. Highly porous morphology of NiO nanocrystallites synthesized at low F/O ratio (0.5) was evident from scanning electron micrograph (SEM). Transmission electron microscopy (TEM) studies showed polycrystalline nature of the material. NiO nanocrystallites exhibit high thermal stability, which was revealed from thermal analysis. The maximum specific capacitance obtained for NiO synthesized at different F/O ratios ranged from 215.6 to 99.2 C/g at 5 mV/s scan rate and 174.7 to 73.0 C/g at 10 A/g current density. Highest value of specific capacitance and lowest values of equivalent series resistance and charge transfer resistance were exhibited by NiO synthesized at low F/O ratio of 0.5. The enhanced electrochemical performance of the sample synthesized at low F/O ratio was benefited mainly from its high surface area and optimal pore size for the diffusion of ions and electrons within the electrode. An asymmetric device fabricated using NiO as the positive electrode and activated carbon derived from phyllanthus emblica as the negative electrode and 3 M KOH as the electrolyte delivered an energy density of 12 Wh/kg at a power density of 427 W/kg.

Synthesis and electrochemical characterization of polyaniline doped cadmium oxide (PANI-CdO) nanocomposites for supercapacitor applications

High-performance nanoscale supercapacitor (SC) electrode materials of polyaniline (PANI) and polyaniline cadmium oxide (PANI-CdO) composites are fabricated using In-situ chemical polymerization route. The structural parameters, crystallite size, and lattice strain of the prepared samples are estimated by X-ray diffraction analysis. The CdO stretching peak in PANI-CdO nanocomposite's FTIR spectra confirms the interaction of CdO with PANI. SEM analysis exposing a random dispersion of CdO nanoparticles in PANI matrix and showing the cluster of indefinitely shaped fibrous flaky architectures. The cyclic voltammetry (CV) results show a higher specific capacitance of 866 F g−1 for PANI-5%CdO composite as compared to Pure PANI 222 F g−1 and Pristine CdO 35.2 F g−1 at 5 mV s−1 scan rate. Galvanostatic charge-discharge (GCD) results also show a higher specific capacitance value of 906.8 F g−1 for PANI-5%CdO composite at 9.26 A g−1 current density revealing a maximum energy density and power density of 9.04 Wh kg−1 and 1510 W kg−1 respectively. The frequency response behavior of PANI-CdO nanocomposites (EIS spectra) reveals (Warburg) diffusive resistance of the electrolyte into the interior of the electrode and ion diffusion into the electrode surface. The higher capacitance and lower ESR (equivalent series resistance) value of PANI-CdO nanocomposite refer to the formation of a more ordered structure and rapid ion diffusion that can develop enhanced surface-dependent electrochemical properties and recommend this material to be a promising potential candidate for practical supercapacitor electrode preparation.

Characterization of cellulose-nanofiber-modified fibrillated lyocell fiber separator

A fibrillated lyocell fiber-based separator was prepared using lyocell fibers and was modified with cellulose nanofibers. The effects of the cellulose nanofiber addition on the tensile properties, electrical properties, pore structure, liquid absorption properties, and equivalent series resistance of the separators were studied. It was found that adding an appropriate amount of cellulose nanofibers to the fibrillated lyocell fiber separator can improve the tensile strength, elongation at break, breakdown voltage, and equivalent series resistance value of the separator; reduce the pore size and porosity of the separator; and improve the pore size distribution. Moreover, the separator modified with 4% cellulose nanofibers yielded a favorable combination of properties, with a tensile strength of 0.645 kN/m, a mean flow pore diameter of 0.771 μm, a porosity of 88.4%, a capillary rise in paper of 30.7 mm/10 min, and an equivalent series resistance value of 2.46 Ω.

A Ten-Minute Synthesis of α-Ni(OH)2 Nanoflakes Assisted by Microwave on Flexible Stainless-Steel for Energy Storage Devices.

Although numerous methods have been widely used to prepare nickel hydroxide materials, there is still a demand for lowering the required heating time, temperature, and cost with maintaining a high-quality nanomaterial for electrochemical energy storage. In this research, we study the relationship between microwave-assisted heating parameters and material properties of nickel hydroxide nanoflakes and evaluate their effect on electrochemical performance. X-ray diffraction spectra show that the samples prepared at the highest temperature of 220 °C have crystallized in the beta phase of nickel hydroxide crystal. While the sample synthesized at 150 °C in 30 min contains both beta and alpha phases. Interestingly, we obtained the pure alpha phase at 150 °C in just 10 min. A scanning electron microscope shows that increasing the temperature and heating time leads to enlarging the diameter of the macro-porous flower-like clusters of interconnected nanoflakes. Electrochemical measurements in potassium hydroxide electrolytes demonstrate that the alpha phase’s electrodes have much higher capacities than samples containing only the beta phase. The maximum areal capacity of 17.7 µAh/cm2 and gravimetric capacity of 35.4 mAh/g are achieved, respectively, at 0.2 mA/cm2 and 0.4 A/g, with a small equivalent series resistance value of 0.887 ohms on flexible stainless-steel mesh as a current collector. These improved nickel hydroxide electrodes can be ascribed to utilizing the diffusion-controlled redox reactions that are detected up to the high scan of 100 mV/s. Such fast charge-discharge processes expand the range of potential applications. Our nickel hydroxide electrode, with its rapid preparation at medium temperature, can be a cost-effective candidate for flexible supercapacitors and batteries.

Failure Region Estimation of Linear Voltage Regulator using Model-based Virtual Sensing and Non-invasive Stability Measurement

Voltage regulator (VR) stability plays an essential role in ensuring maximum power delivery and long-lasting electronic lifespan. Capacitor with a specific equivalent series resistance (ESR) range is typically connected at the VR output terminal to compensate for instability of the VR due to sudden changes in load current. The stability of VR can be measured by analyzing output voltage during load transient tests. However, the optimum ESR range obtained from the ESR tunnel graph in its datasheet can only be characterized by testing a set of data points consisting of ESR and load currents. Characterization process is performed manually by changing the value of ESR and load current for each operating point. However, the inefficient process of estimating the critical value of ESR must be improved given that it requires a large amount of time and expertise. Furthermore, the stability analysis is currently conducted on the basis of the number of oscillation counts of VR output voltage signal. Therefore, a model-based virtual sensing approach that mainly focuses on black-box modeling through system identification method and training neural network on the basis of estimated transfer function coefficients is introduced in this study. The proposed approach is used to estimate the internal model of the VR and reduce the number of data points that need to be acquired. In addition, the VR stability is analyzed using noninvasive stability measurement method, which can measure phase margin from the frequency response of the VR circuit in closed-loop conditions. Results showed that the proposed method reduces the time it takes to produce an ESR tunnel graph by 84% with reasonable accuracy (MSE of 5×10−6, RMSE of 2.24×10−3, MAE of 1×10−3, and R2 of 0.99). Therefore, efficiency and effectiveness of ESR characterization and stability analysis of the VR circuit is improved.

DC-Link Capacitor Diagnosis in a Single-Phase Grid-Connected PV System

The DC-link capacitor is one of the components that are more prone to faults in energy-distributed systems based on voltage source inverters. A predictive maintenance approach should allow to foresee the risk of an unexpected system shutdown. In this study, a two-stage diagnostic approach that is aimed at determining the health status of the DC-link capacitor in a single-phase grid-connected PV system was proposed. The equivalent series resistance (ESR) and the capacitance (C) values were used as indicators in the estimation of the degradation stage. Electrochemical impedance spectroscopy (EIS) was used to estimate the impedance curve of the DC-link capacitor, and a multi-fitting algorithm allowed us to determine the ESR and C parameters. A comparison between the estimated values C and ESR and the nominal values was used to quantify the fault severity. It was demonstrated that the EIS allowed the determination of the capacitor impedance regardless of the actual operating conditions of the photovoltaic generator, such as during irradiance changes and with the maximum power point algorithm turned off. By using the capacitor simplified model and a multi-fitting algorithm, the C and ESR values were estimated with an error that was lower than 1%. An analysis of the hardware required to implement the proposed approach in real applications by achieving the desired accuracy was also proposed.

Finite Element Analysis of Multi-Layer Ceramic Capacitors Improved Self-heating for High Reliability

Heat generation with decrease in multilayer ceramic capacitor (MLCC) device size proves problematic in various fields. Herein, we performed heating temperature measurements according to various MLCC sizes and several finite element analysis (FEA) simulations to improve the self-heating characteristics. For the experiments, 1005, 1608, and 2012 size MLCCs with a 1-µF capacitance were selected, and temperature changes were measured using a ripple current test at 10 kHz. The thermal resistance ( $$R_{t}$$ ) and equivalent series resistance (ESR) of the 1005, 1608, and 2012 MLCCs were determined to be 94 °C/W and 92 mΩ, 86 °C/W and 69 mΩ, and 82 °C/W and 37 mΩ, respectively. The experimental results confirm that the ESR value and MLCC size significantly influence thermal resistance due to ripple current. To improve the heat generation characteristics due to ripple current, an FEA model was constructed considering the dielectrics, conductors, and design parameter characteristics to verify the temperature changes according to ESR and MLCC size. After application of ripple current from the measured ESR value through the ANSYS Maxwell 3D software, the extracted ohmic loss value was converted to the ANSYS Icepak software to verify the temperature change value. Resultantly, a measured temperature change and simulation result error range of within 1% were obtained. For MLCC incorporation in applications such as 5G network equipment and electric vehicles, considering reliability characteristics, the internal stress and heat flux values were analyzed using the ANSYS mechanical software as per temperature change according to MLCC size, volume, and ripple current. The results confirmed that with MLCC volume increase, the internal heat flux increased according to the temperature change, temperature increase was suppressed owing to the smooth heat flux, and the internal stress appeared smaller.

Online Noninvasive Technique for Condition Monitoring of Capacitor in Linear Power Supplies

Linear power supplies (LPSs) are widely used in fields including measurement systems, radiofrequency systems, medical applications, nuclear power plants, and spacecraft electronics. Electrolytic capacitors are used in a variety of devices because of their small size, low cost, and large capacity. During the use of electrolytic capacitor, it is very common for the capacitance (C) to decrease and its equivalent series resistance (ESR) to increase, which are typical indicators of capacitor degradation. Electrolytic capacitors are both the weak link and the core component of the LPSs and play a vital role in determining the LPSs lifetime. Under the power frequency condition, the power frequency transformer plays a role in isolation and voltage reduction in the LPSs. The input and output signals of the LPSs are used for condition monitoring of capacitor, and the existence of transformer increases the difficulty of the online noninvasive technique of LPSs. The online noninvasive technique for condition monitoring of capacitor in LPSs proposed in this article can be solved only by using the input current, the magnetizing current, the input voltage, and the load current. Effect of temperature on C and ESR values is incorporated for accurate determination of the parameters of capacitor. The effectiveness of the proposed method is verified through simulations and experiments, and the data obtained are consistent with the results measured using an LCR meter.

On-Line Fault Diagnosis of DC-Link Electrolytic Capacitors in Boost Converters Using the STFT Technique

Faults in aluminum electrolytic capacitors (AECs) are classified as the major cause for power electronics equipment breakdown, mainly due to AECs wear out through the vaporization of the electrolyte, as a result of both aging and temperature effects. The majority of manufacturers identify the end-of-life threshold of such capacitors as their equivalent series resistance (ESR) increases by 80% or their capacitance (C) decreases by 20%, relative to their initial values. Therefore, the online estimation of these two parameters can provide valuable and timely information that allows detecting any potential capacitor failure. Changes in C and ESR parameters influence the relationship between the capacitor voltage and current ripples. This ratio is dominated by C at low frequencies, and by ESR in the high-frequency range. The aim of this article is to propose an algorithm allowing a continuous estimation and tracking of both parameters (ESR and C). This algorithm should be simple, fast, and suitable for online implementation. Therefore, this article introduces the use of the short-time Fourier transform (STFT) technique to determine and track C and ESR values, starting from some always-existing harmonics at low and high frequencies. The STFT is based on applying the discrete Fourier transform algorithm on a sliding window, which makes it more appropriate for online implementation. The effectiveness of the proposed method is proved by simulation and laboratory experiments, using a boost dc-dc converter.

Carbon nanocomposite electrodes for electrical double layer capacitor

Abstract Activated carbons (ACs) have been used as electrode material in commercial electric double-layer capacitors (EDLC) due to their low cost, high specific surface area, and chemical stability. Unfortunately, the supercapacitive performance of AC is not satisfactory due to their low conductivity.On the other hand, carbon nanofibers (CNFs) based EDLC exhibit low equivalent series resistance (ESR) but not such energy storage values as AC ones. Here in this paper, we report on the synthesis of new nanocomposites based on a mixture of ACs and CNFs using a simple powder processing route and evaluating their electrochemical behavior as electrode materials in symmetric EDLC. The EDLC, with 10 wt. % CNFs in AC/CNFs as the electrodes have displayed a high conductivity and surface area resulting in the enhancement of the energy and power delivers in aqueous electrolyte. On the contrary, with 90 wt.% CNFs in AC/CNFs as the electrodes, higher specific power, low ESR, and low value of relaxation time constant are achieved. The highest value of specific capacitance estimated is around 207 F g−1 at 5 mV s−1 and the highest specific energy is 13.2 Wh kg−1 at 1 A g−1 for the 10 wt.% CNFs in AC/CNFs.

Metal framework as a novel approach for the fabrication of electric double layer capacitor device with high energy density using plasticized Poly(vinyl alcohol): Ammonium thiocyanate based polymer electrolyte

High performance electric double-layer capacitors (EDLCs) based on poly (vinyl alcohol) (PVA): ammonium thiocyanate (NH4SCN):Cu(II)-complex plasticized with glycerol (GLY) have been fabricated. The maximum DC ionic conductivity (σDC) of 2.25 × 10-3 S cm−1 is achieved at ambient temperature. The X-ray diffraction (XRD) patterns confirmed that the addition of both Cu(II)–complex and GLY enhanced the amorphous region within the samples. Through the Fourier transform infrared (FTIR) the interactions between the host polymer and other components of the prepared electrolyte are observed. The FESEM images reveal that the surface morphology of the samples showed a uniform smooth surface at high GLY concentration. This is in good agreement with the XRD and FTIR results. Transference numbers of ion (tion) and electron (tel) for the highest conducting composite polymer electrolyte (CPE) are recognized to be 0.971 and 0.029, respectively. The linear sweep voltammetry (LSV) revealed that the electrochemical stability window for the CPE is 2.15 V. These high values of tion and potential stability established the suitability of the synthesized systems for EDLC application. Cyclic voltammetry (CV) offered nearly rectangular shape with the lack of Faradaic peak. The specific capacitance and energy density of the EDLC are nearly constant within 1000 cycles at a current density of 0.5 mA/cm2 with average of 155.322F/g and 17.473 Wh/Kg, respectively. The energy density of the EDLC in the current work is in the range of battery specific energy. The EDLC performance was found to be stable over 1000 cycles. The low value of equivalent series resistance reveals that the EDLC has good electrolyte-electrode contact. The EDLC exhibited the initial high power density of 4.960 × 103 W/Kg.

Efficient method to investigate the equivalent series resistance of a capacitor in low frequency range

The equivalent series resistance (ESR) is an important parameter for determining the quality of a capacitor. In general, the value of the ESR can be obtained only at a single frequency point during mass production testing, because obtaining the whole ESR curve by means of scanning the frequency range is time consuming. We present a novel method to investigate how the ESR varies with frequency during batch testing. We use the multi-frequency synthesis excitation waveform to obtain the ESR at multiple frequency points. This allows the entire ESR curve to be obtained during one measurement period, thus greatly improving the measurement speed. The mathematical principle, the circuit realisation and the signal processing algorithm are discussed. Furthermore, a principle verification test is conducted, and the ESR values at seven frequency points are synchronously measured. The obtained results are consistent with those acquired from a standard LCR meter, and the entire measurement is completed within 10 ms, which confirms that our method is efficient and suitable for measurements in the mass production testing.