Polypyrrole as a solid electrolyte for tantalum capacitors

DC link electrolytic capacitors are widely used in various PWM power converter system, such as adjustable speed driver(ASD) or DC/DC converter. Electrolytic capacitors, which is the most of the time affected by aging effect, plays a very important role for the power electronics system quality and reliability. This objective of this paper is to propose a improvement method to detect the rise of equivalent series resistor(ESR) in order to realize the online failure prediction of electrolytic capacitor for DC link of PWM power converter. The ESR detection scheme is based on the determination of the electrolytic capacitor AC losses calculated from voltage/current measurement using AC coupling. Therefore, the preposed online failure prediction method has the merits of easy ESR computation and circuit simplicity compare with BPF method. Simulation results show the veridity of the proposed on-line ESR estimation method.

The discrete mapping model of current‐mode controlled buck converter with constant current load, taking account of composite output capacitors (parallel connection of two different types of capacitor branches, i.e. electrolytic capacitors and ceramic capacitors), is established. Based on the model, dynamical effects of varying output capacitance and equivalent series resistance (ESR) are investigated by bifurcation behaviours. The period of low‐frequency oscillation among coexisting fast‐slow scale instability is derived by exploring the loci of eigenvalues, while the operating regions are estimated. Time‐domain simulation and experimental waveforms are provided for verification of the theoretical analysis, indicating the existences of subharmonic oscillation and coexisting fast‐slow scale instability in the converter with variation of output capacitance and ESR. Research results reveal that the low‐frequency oscillation can be eventually eliminated due to a relatively large (or small) ESR and the capacitance in the same branch presents to identical tendency of dynamical effects on the converter. Moreover, the interaction effects between two parallel capacitor branches are demonstrated. It illustrates that the low‐frequency oscillation can be removed with smaller (or larger) ESR or capacitance in one branch of the composite output capacitors while larger (or smaller) ESR or capacitance in the other branch.

Due to their substantial energy density and economical pricing, switching-mode power supplies (SMPSs) often utilize electrolytic capacitors. However, their ability to function at low temperatures is essential for dependable operation in several sectors, including telecommunications, automotive, and aerospace. This study includes an experimental evaluation of how well standard SMPS electrolytic capacitors operate at low temperatures. This paper investigates the suitability of standard electrolytic capacitors used in switched-mode power supplies (SMPSs) for low-temperature applications. The experimental evaluation exposed the capacitors to temperatures ranging from −5 °C to −40 °C, assessing capacitance (Cp), impedance (Z), dissipation factor (DF), and equivalent series resistance (ESR) at each temperature. The capacitor’s time-domain electrical signals were analyzed using the Pearson correlation coefficient to extract discriminative features. These features were input into an artificial neural network (ANN) for training and testing. The results indicated a significant impact of low temperatures on capacitor performance. Capacitance decreased with lower temperatures, while the ESR and leakage current increased, affecting stability and efficiency. Impedance was a valuable diagnostic tool for identifying potential capacitor failure, showing a 98.44% accuracy drop at −5 °C and 88.75% at the peak temperature, indicating proximity to the manufacturer’s specified limit. The study suggests further research and development to improve the performance of electrolytic capacitors in SMPS systems under cold conditions, aiming to boost efficiency and reliability.

Electrolytic power capacitors have been widely used in power conversion system such as inverter or UPS because of characteristics of large capacitance, high-voltage and low-cost. The electrolytic capacitor, which is most of the time affected by the aging effect, plays a very important role for the power-electronics system quality and reliability. Therefore it is important to diagnosis monitoring the condition of an electrolytic capacitor in real-time to predict the failure. In this paper, the on-line remote diagnosis monitoring system for UPS DC link electrolytic capacitors using low-cost single-chip zigbee communication modules is developed. To estimate the health status of the capacitor, the equivalent series resistor(ESR) of the component has to be determined. The capacitor ESR is estimated by using RMS computation using BPF modeling of DC link ripple voltage/current. Zigbee-based hardware experimental results show that the proposed remote capacitor diagnosis monitoring system can be applied to UPS successfully. BR

The demand for power sources for electric vehicles and portable devices has increased rapidly. All-solid-state lithium-ion batteries are promising attention due to their safety and energy density. Especially, the development of solid electrolytes is necessary to realize all-solid-state batteries. Solid electrolytes with high ionic conductivity like sulfides, oxides, and chlorides are used for long-distance conduction in the entire all-solid-state batteries. In addition, those with low ionic conductivity like lithium salts are also used as coating materials and sintering aids. Our group reported active materials and electrolytes using Li2SO4 [1, 2].One of the features required for solid electrolytes is wide electrochemical windows. Although various sulfide solid electrolytes have been studied due to their high ionic conductivity and ductility, they have narrow electrochemical windows [3], leading to oxidative and reductive decomposition during cell cycling. Thus, it is important to consider the electrochemical windows of solid electrolytes.Conventionally, the electrochemical windows of solid electrolytes have been investigated using electrochemical techniques like cycling voltammetry and linear sweep voltammetry (LSV). The working electrode is composed of the objective solid electrolytes and conductive carbon. However, for some materials with low ionic conductivity, it is challenging to ensure ionic conduction at long distances in the composite working electrode. Therefore, few reports have shown that the redox potential of a low ionic-conductive material including Li2SO4 is experimentally determined by electrochemical tests, although the electrochemical stability of lithium ion conductors was investigated using first-principles calculation methods [3, 4].In this study, we used LSV measurements using all-solid-state cells to investigate the redox potential of Li2SO4. The composite working electrode comprised Li2SO4, vapor-grown carbon fiber (VGCF), and oxide solid electrolyte. Li2SO4 and VGCF were ball-milled and the obtained Li2SO4-VGCF and oxide electrolyte were mixed in an agate mortar and pestle to prepare composite working electrodes. As oxide electrolytes, 90Li3BO3·10Li2SO4 glass-ceramic (LBSO) [2] was used in cells for an anodic scan, and 67Li2O·33LiI glass (LOI) [5] was used in cells for a cathodic scan because they have better oxidation or reduction tolerance than sulfide electrolytes. In addition, it was found that the decomposition of sulfide electrolytes affected the LSV curves when sulfide electrolytes were used in a composite working electrode or as a separator layer that directly contacted with the composite working electrode. Therefore, the cell configuration was Li-In/Li3PS4/LBSO (or LOI)/Li2SO4-VGCF-LBSO (or LOI). To confirm the decomposition of Li2SO4 after the LSV measurements, X-ray photoelectron spectroscopy (XPS) measurements were performed on the cells, and the redox mechanism of Li2SO4 was discussed.In the anodic scan, a current peak derived from the oxidation of Li2SO4 was observed at approximately 4.3 V vs. Li-In (4.9 V vs. Li+/Li), which was close to the standard electrode potential of oxidation from SO4 2– to S2O8 2– [6]. In addition, in the cathodic scan, a current peak derived from the reduction of Li2SO4 was observed at approximately 1.5 V vs. Li-In (2.1 V vs. Li+/Li), which almost corresponds to the potential of reduction from SO4 2– to SO3 2– [6]. Furthermore, the XPS analyses confirmed that Li2SO4 was finally reduced to Li2S and Li2O.In summary, the LSV measurements were performed with the all-solid-state cell using oxide electrolytes instead of sulfide electrolytes, which eliminated the overlap of a current caused by the decomposition of sulfide electrolytes. The oxidative and reductive decomposition voltages of Li2SO4 were close to each standard electrode potential. We also found a way to experimentally determine the electrochemical potential of any materials by modifying the cell design. This study will help spread the importance of potential windows and the realization of all-solid-state lithium-ion batteries. Reference s : [1] K. Nagao et al., Sci. Adv. 6 (2020) eaax7236.[2] M. Tatsumisago et al., JCS-Japan, 125 (2017) 433.[3] Y. Zhu et al., ACS Appl. Mater. Interfaces, 7 (2015) 23685.z[4] W. D. Richards, et al., Chem. Mater., 28 (2016) 266.[5] Y. Fujita et al., Electrochemistry, 89 (2021) 334.[6] A. J. Bard et al., Standard Potentials in Aqueous Solution, Routledge (2017).

An online condition monitoring method is presented for electrolytic capacitors health condition based on state observer method. With this method, both capacitance and equivalent series resistor in an electrolytic capacitor can be estimated online without disassembly from power converter systems. The method is with high precision without any additional hardware in application. The estimated capacitance and equivalent series resistor can be used to predict the rest useful life of the electrolytic capacitors and provide the suitable time for preventive maintenance. The method was verified by both simulation analysis and prototype testing. Experiment results shown a high precision results with relative error of less than 3%

The object of this paper is to present an economic electronic module integrated on an electrolytic capacitor that is able to indicate the moment when it must be changed. First, with a switchmode power supply as an example, the high probability of electrolytic capacitor failure with respect to other power components is noted. Second, the authors recall that the increase of the equivalent series resistance (ESR) of the capacitor is the best indicator of their faulty state. From the measurements of the voltage ripple and the capacitor current, one can deduce the ESR; the latter is compared to the ESR value of the sound capacitor deduced from the component case temperature. Thus, the capacitor deterioration can be diagnosed.

Na like super ionic conductors (NASICON)-structure Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte have attracted attention as high ion conductivity and chemical stability. The M1–M2 voids between the TiO6 octahedra and PO4 tetrahedra in a Li1.3Al0.3Ti1.7(PO4)3-based solid electrolyte is a major path for lithium-ion conduction, and it can be widened to increase lithium-ion conductivity by doping. In this study, divalent ions are doped into the Li1.3Al0.3Ti1.7(PO4)3-based electrolyte and widened ion-conduction path and improved ion conductivity. Making doped Li1.3Al0.3Ti1.7(PO4)3 samples starts with melting, then transformed into glass, pulverized, and then subjected to uniaxial compression molding and sintering, after which they are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and their impedance resistances were measured. The LiTi2(PO4)3 is generated by thermal treatment and crystallized to form an electrolyte whose lattice parameter values depend on the dopant ion and its content, with each divalent ion distorting the lattice and the M1–M2 bottleneck structure differently. Only Mg2+ doping led to a structural change that increases Li-ion conductivity to 1.55 × 10−3 S/cm at 5 mol% of magnesium ion, with the observed threefold increase in conductivity compared to the 4.73 × 10−4 S/cm ion conductivity of LATP ascribable to a widening of the ion-conduction path. Overall, doping an LATP-based solid electrolyte with an appropriate divalent cation is a promising way of improving performance in a manner that has various applications.

Open-pore nickel (Ni) foams are characterized using surface science and electrochemical techniques. A scanning electron microscopy analysis reveals interconnected Ni struts that generate small and large pores of ca. 50 and 500 μm in size, respectively. An X-ray photoelectron spectroscopy (XPS) analysis of the surface-chemical composition of the Ni foams shows that there are oxidized and metallic sections within their surfaces despite being prepared by sintering in an oxidizing atmosphere at a high temperature and being stored in moist air. The ratio of the areas of oxidized and metallic sections is evaluated using XPS data. Chemical etching of the Ni foams results in removal of the native surface oxide/hydroxide without altering the three-dimensional structure; it also increases the roughness (R) of the surfaces of Ni struts giving rise to an increase in the electrochemically active surface area (Aecsa). Thermal treatment of Ni foams in an H2(g) atmosphere at 500 °C reduces the native surface oxide/hydroxide but does not increase R or Aecsa. Electrochemical behavior of the Ni foams is examined in 0.5 M aqueous KOH solution using cyclic-voltammetry (CV) and electrochemical impedance spectroscopy (EIS). As-received, chemically etched, thermally reduced and electro-oxidized Ni foams generate distinct CV profiles; their features are assigned to oxidized and metallic surface states. The observations made on the basis of XPS measurements are corroborated by the results of CV analyses. The application of CV and XPS or EIS allows in situ determination of Aecsa and the specific surface area (As) of the chemically etched and thermally reduced Ni foams. The values of As determined on the basis of joint CV and XPS measurements are 227 ± 74 and 149 ± 48 cm(2) g(-1) for the etched and reduced Ni foams, respectively. The values of As determined on the basis of CV, XPS and EIS measurements are 241 ± 80 and 160 ± 23 cm g(-1) for the etched and reduced Ni foams, respectively.

This paper proposes an online condition monitoring system for aluminum electrolytic capacitors used as dc-link capacitors in industrial power converters. Electrolytic capacitors are one of the most fragile components of a power converter system because of their wear-out failures and short lifespan. Therefore, the use of condition monitoring systems for aluminum electrolytic capacitors allow preventive maintenance to be performed, thereby avoiding unexpected shutdown and downtime. The dominant wear-out mechanisms in aluminum electrolytic capacitors are characterized by the increase in equivalent series resistance. Hence, the condition monitoring system proposed in this paper is based on the online estimation of the capacitor's equivalent series resistance using the switching frequency components of the dc-link capacitor voltage and current. The equivalent series resistance estimation method is tested using the PSpice circuit simulator and is validated experimentally using a custom-made inverter. Finally, the equivalent series resistance estimation method is adapted for the condition monitoring of capacitors in industrial power converters and the proposed condition monitoring system is implemented in a commercial ac drive system to prove the applicability of the proposed method to industrial power converters.

This paper proposes the experiments and setups for studying diagnosis and prognosis of electrolytic capacitors in DC-DC power converters. Electrolytic capacitors and power MOS-FET's have higher failure rates than other components in DC-DC converter systems. Currently, our work focuses on experimental analysis and modeling electrolytic capacitors degradation and its effects on the output of DC-DC converter systems. The output degradation is typically measured by the increase in Equivalent series resistance and decrease in capacitance leading to output ripple currents. Typically, the ripple current effects dominate, and they can have adverse effects on downstream components. A model based approach to studying degradation phenomena enables us to combine the physics based modeling of the DC-DC converter with physics of failure models of capacitor degradation, and predict using stochastic simulation methods how system performance deteriorates with time. Degradation experiments were conducted where electrolytic capacitors were subjected to electrical and thermal stress to accelerate the aging of the system. This more systematic analysis may provide a more general and accurate method for computing the remaining useful life (RUL) of the component and the converter system.

Enhanced longterm stability of aluminum solid electrolyte capacitor containing thiophene derivatives as a solid electrolyte

Effect of the surface chemistry of activated carbon on its electrochemical properties in electric double layer capacitors

This paper shows a system to measure the Equivalent Series Resistance (ESR) and Capacitance (C) of capacitors. This system provides a cost effective solution for Prognostic Health Monitoring (PHM) of capacitors used in fully electric vehicles (FEV) and medium-power switching supplies. The system is based on a Hartley resonant topology formed by two inductors and a variable capacitor. This circuit is able to measure Metalized Thin Film Capacitors (MTFC) as well as electrolytic capacitors. The paper analyzes the circuit and compares the results of simulations and experiments.

Variation of electrochemical performance of Li2ZrCl6 halide solid electrolyte with Mn substitution for all-solid-state batteries