TY - JOUR A1 - Kurzweil, Peter A1 - Scheuerpflug, Wolfgang T1 - State-of-charge monitoring and battery diagnosis of different lithium ion chemistries using impedance spectroscopy JF - Batteries N2 - For lithium iron phosphate batteries (LFP) in aerospace applications, impedance spectroscopy is applicable in the flat region of the voltage-charge curve. The frequency-dependent pseudocapacitance at 0.15 Hz is presented as useful state-of-charge (SOC) and state-of-health (SOH) indicator. For the same battery type, the prediction error of pseudocapacitance is better than 1% for a quadratic calibration curve, and less than 36% for a linear model. An approximately linear correlation between pseudocapacitance and Ah battery capacity is observed as long as overcharge and deep discharge are avoided. We verify the impedance method in comparison to the classical constant-current discharge measurements. In the case of five examined lithium-ion chemistries, the linear trend of impedance and SOC is lost if the slope of the discharge voltage curve versus SOC changes. With nickel manganese cobalt (NMC), high impedance modulus correlates with high SOC above 70%. KW - battery life testing KW - capacitance KW - lithium-ion battery KW - state-of-charge determination KW - state-of-health KW - pseudocharge KW - impedance spectroscopy KW - aging Y1 - 2021 U6 - https://doi.org/10.3390/batteries7010017 VL - 7 IS - 1 ER - TY - JOUR A1 - Kurzweil, Peter A1 - Schottenbauer, Josef A1 - Schell, Christian T1 - Past, Present and Future of Electrochemical Capacitors: Pseudocapacitance, Aging Mechanisms and Service Life Estimation JF - Journal of Energy Storage N2 - The capacitance values printed on capacitor housings do not reflect the actual capacitance available for any technical application. The complex properties of the pseudocapacitance and the aging behavior of practical supercapacitors are reviewed with regard to the state-of-the-art and the latest findings. The long-term stability of various electrolyte systems and carbon materials is critically examined under phenomenological aspects that reflect the typical fault pattern of supercapacitors. Electrolyte resistance and voltammetric capacitance are reliable aging indicators. High temperatures have a greater impact on service life than high voltages, and overvoltages are worse than high currents. The anode more than the cathode suffers from a loss of pore volume, increase of nitrogen and fluorine compounds, and the unstable adhesive layer between active carbon and aluminum. Unwanted material changes and chemical reactions in the supercapacitor reflect the influence of water over several years in the life test. Credible reaction pathways are identified for the known aging processes. Fundamentals and materials are reviewed in a separate part.** KW - Electrochemical double-layer capacitors KW - Supercapacitor KW - Capacitance KW - Pseudocapacitance KW - Aging mechanisms KW - Carbon degradation KW - State-of-health Review KW - Review Y1 - 2020 U6 - https://doi.org/10.1016/j.est.2021.102311 VL - 35 IS - March PB - Elsevier ER - TY - JOUR A1 - Bodnaruk, A1 - Andrii V., A1 - Brunhuber, Alexander A1 - Kalita, Viktor M. A1 - Kulyk, Mykola M. A1 - Kurzweil, Peter A1 - Snarskii, Andrei A. A1 - Lozenko, Albert F. A1 - Ryabchenko, Sergey M. A1 - Shamonin (Chamonine), Mikhail T1 - Magnetic anisotropy in magnetoactive elastomers, enabled by matrix elasticity JF - Polymer N2 - Polydimethylsiloxane based magnetoactive elastomers demonstrate above the melting transition range (e.g. at room temperature) an induced uniaxial magnetic anisotropy, which grows with increasing magnetic field. By freezing a material down to 150 K, displaced iron microparticles are immobilized, so that the magnetic anisotropy can be measured. Magnetic anisotropy “constant” is a consequence of particle displacements and a characteristic of the energy of internal deformations in the polymer matrix. The maximum anisotropy constant of the filling is at least one order of magnitude larger than the shear modulus of the pure elastomer (matrix). In a magnetic field, the gain in the rigidity of the composite material is attributed to the magnetomechanical coupling, which is in turn a source of anisotropy. The concept of effective magnetic field felt by the magnetization allows one to explain the magnetization curve at room temperature from low-temperature measurements. The results can be useful for developing vibration absorbers and isolators. KW - Experimental methodology KW - Internal deformation KW - magnetic properties KW - magnetoactive elastomer KW - Magnetomechanical coupling KW - magnetorheological elastomer Y1 - 2019 U6 - https://doi.org/10.1016/j.polymer.2018.12.027 VL - 162 IS - January SP - 63 EP - 72 PB - Elsevier ER - TY - JOUR A1 - Kurzweil, Peter A1 - Shamonin (Chamonine), Mikhail T1 - State-of-Charge Monitoring by Impedance Spectroscopy during Long-Term Self-Discharge of Supercapacitors and Lithium-Ion Batteries JF - Batteries N2 - Frequency-dependent capacitance C(ω) is a rapid and reliable method for the determination of the state-of-charge (SoC) of electrochemical storage devices. The state-of-the-art of SoC monitoring using impedance spectroscopy is reviewed, and complemented by original 1.5-year long-term electrical impedance measurements of several commercially available supercapacitors. It is found that the kinetics of the self-discharge of supercapacitors comprises at least two characteristic time constants in the range of days and months. The curvature of the Nyquist curve at frequencies above 10 Hz (charge transfer resistance) depends on the available electric charge as well, but it is of little use for applications. Lithium-ion batteries demonstrate a linear correlation between voltage and capacitance as long as overcharge and deep discharge are avoided. KW - aging KW - capacitance KW - self-discharge KW - state-of-charge monitoring KW - supercapacitor Y1 - 2018 U6 - https://doi.org/10.3390/batteries4030035 VL - 4 IS - 3 SP - 1 EP - 13 PB - MPDI ER - TY - JOUR A1 - Kurzweil, Peter A1 - Shamonin (Chamonine), Mikhail A1 - Udalzow, Anton T1 - Selbstentladung und Leckstromverhalten elektrochemischer Speicher: Impedanzspektroskopie im Langzeitversuch JF - Forschungsbericht 2016 / OTH Amberg-Weiden N2 - Doppelschichtkondensatoren sind elektrochemische Speicher, die innerhalb von Mikrosekunden auf schnelle Laständerungen antworten. Auf der Basis einer mehr als zehnjährigen Testerfahrung unserer Arbeitsgruppe sind wir in der Lage, das Alterungsverhalten von Superkondensatoren anhand von Kapazitätsverlust, parasitären Nebenreaktionen und der chemischen Analyse von Alterungsprodukten zu quantifizieren. Weitgehend ungeklärt sind die elektrochemischen Mechanismen bei der Selbstentladung der Bauteile, die wir nun mithilfe der Impedanzspektroskopie näher untersucht haben . Double-layer capacitors are electrochemical storage devices that are able to respond to immediate load changes within some microseconds. Based on more than ten years testing experience of our work group, the aging behaviour of supercapacitors is quantified in terms of capacitance loss, parasitic side reactions, and the chemical analysis of decomposition products. So far, the electrochemical processes during self-discharge have been widely unknown. By the help of impedance spectroscopy, we investigated this item in more detail. Y1 - 2016 UR - https://www.oth-aw.de/files/oth-aw/Aktuelles/Veroeffentlichungen/Forschungsbericht/Forschungsbericht_2016.pdf SN - 2365-1997 SP - 90 EP - 94 PB - Ostbayerische Technische Hochschule Amberg-Weiden ER -