Galvanische Abscheidung von Nickel-Chrom-Legierungsschichten. - In: WOMag, ISSN 2195-5891, Bd. 10 (2021), 10, S. 21-24
TU Ilmenau startet DFG-Projekt zur Optimierung von Lithiumionenbatterien. - In: WOMag, ISSN 2195-5891, Bd. 10 (2021), 7/8, S. 13
Investigation of the contact resistance as a function of the temperature for connectors and wire terminals. - In: 30th International Conference on Electrical Contacts, (2021), S. 202-209
The hardness of coating materials such as tin or gold is temperature-dependent, so the contact area and thus the contact resistance change depending on the temperature. Contact resistance measurements are carried out on hard gold- and tin-coated connector contacts at elevated temperatures. It is shown that the contact resistance decreases significantly with increasing temperature. Tests are also being carried out with solid and stranded copper wires. In addition to the hardness, foreign layers on the copper conductors have a further influence on the contact resistance.
https://doi.org/10.22032/dbt.51522
Simulation verschiedener Hull-Zellen-Geometrien, Teil 1 - spezielle Elektrodengeometrien in 2D und 3D. - In: Galvanotechnik, ISSN 0016-4232, Bd. 112 (2021), 10, S. 1315-1323
Development of a dynamic model of lithium ion battery pack for battery system monitoring algorithms in electric vehicles. - In: 2021 23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe), (2021), S. P.1-P.10
The main objective of this paper is to develop an accurate and a self-corrective model for lithium ion battery pack, based on the analysis of properties and performance of equivalent circuit models of pack's cells and the use of artificial neural networks. This model is expected to meet the requirements for improving the accuracy of battery state estimation required for the monitoring algorithms of the battery system in electric vehicles.The use of the neural network will make it possible to adjust and correct modelling deviations and errors in equivalent circuit model parameters by comparing the modelled cells voltage and the measured voltage and generating modified model parameters based on this comparison.The validation experimental results show that the parameters of the modified model contributed to reducing the error rate in the cell voltage by approximately 70-80% of the error rate in the equivalent circuit model voltage.
https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570709
Corrosion of aluminium current collector in lithium-ion batteries: a review. - In: Journal of energy storage, ISSN 2352-152X, Bd. 43 (2021), 103226
Calendar and cycle ageing affects the performance of the lithium-ion batteries from the moment they are manufactured. An important process that occurs as a part of the ageing is corrosion of the current collectors, especially prominent in the case of the aluminium substrate for the positive electrode. Generally, aluminium resists corrosion due to the formation of a non-permeable film of native aluminium oxide. Nevertheless, at certain electrochemical conditions corrosion affects the interface of the current collector. As a consequence of corrosion, the cathode materials lose electrical and mechanical contact with the current collector, leading to capacity and power fading. Therefore, a deeper understanding of this process and effective corrosion inhibition are necessary to prevent the deterioration of the battery performance. This review provides an updated critical overview of the mechanisms of aluminium corrosion, methodologies for analysing this phenomenon, and approaches for its effective mitigation. As the influence of multiple factors on the corrosion process has a central impact, the review discusses how they specifically affect the undergoing processes. Therefore, appropriate examples of important factors like electrolyte composition, thermal conditions and electrochemical parameters are presented to explain the specific mechanism of aluminium corrosion. Since corrosion inhibition is an important technological issue with a tremendous economic impact the review summarises how to achieve this by adjusting the electrochemical system and enhancing the knowledge on the safe operation of the positive electrode.
https://doi.org/10.1016/j.est.2021.103226
Efficient preparation of Ni-M (M = Fe, Co, Mo) bimetallic oxides layer on Ni nanorod arrays for electrocatalytic oxygen evolution. - In: Applied materials today, ISSN 2352-9407, Bd. 25 (2021), 101185
Fabrication of economic and high-performance electrodes for electrocatalytic oxygen evolution reaction (OER) accounts for a crucial issue associated with developing powerful and practical water splitting systems. In this work, free-standing Ni/Ni-M (M = Fe, Co, Mo) bimetallic oxides core/shell nanorod arrays (Ni/Ni-M NRAs) were prepared through electroless deposition of transition metal species on black nickel sheet (nickel nanorod arrays (Ni NRAs)) followed by electrochemical oxidation. All three types of Ni/Ni-M NRAs demonstrated enhanced electrocatalytic activity toward oxygen evolution reactions (OER). Especially, Ni/Ni-Fe NRAs electrode exhibit small onset potential of 1.535 V at current density of 10 mA&hahog;cm^-2. In contrast, the OER durability of these three samples was distinct. At 500 mV constant overpotential, the current density loss in OER of Ni/Ni-Fe NRAs was merely 13.5% for a period of 20000 s; but Ni/Ni-Mo and Ni/Ni-Co NRAs had almost disappeared catalytic activity under the identical conditions. According to many reports, the results were different for the superior OER stability of Ni-based bimetallic catalysts. Electrochemical analysis revealed that the NRAs structure dramatically improves charge transfer efficiency and electrochemically active surface area (ECSA). The present study might provide a new insight to design and fabricate more practical and high-performance Ni-based electrodes for OER.
https://doi.org/10.1016/j.apmt.2021.101185
Developing an advanced equivalent circuit model for a Li-ion battery for battery monitoring in electric vehicles. - In: PCIM Europe Digital Days 2021, (2021), S. 1493-1498
In the improved second-order equivalent circuit model (ECM) presented in this paper, the battery responses to operational (voltage and current) and non-operational (ambient temperature) parameters were taken into account to reach high accuracy to improve the estimation of state of charge (SOC) and state of health (SOH) of lithium–ion batteries (LIBs) of electric vehicles (EVs). Based on this model, the exponential-function fitting method is adopted to identify the battery parameters according to the test data collected from the experimental platform. The performance of the model is verified by comparing the experimental and simulated voltage under hybrid pulse power characterization (HPPC) test profile.
https://ieeexplore.ieee.org/document/9472423
Elektrochemische Abscheidung von Aluminium und Aluminiumlegierungen aus ionischen Flüssigkeiten. - Ilmenau : Universitätsbibliothek, 2021. - 1 Online-Ressource (xiii, 100, LIX Seiten)
Technische Universität Ilmenau, Dissertation 2021
Die galvanische Abscheidung von Aluminium aus ionischen Flüssigkeiten (ILs) hat großes Potential für den Ersatz umweltbedenklicher Cd-Beschichtungen. Aufgrund der Ausbildung der natürlichen Al2O3 Schicht bei Kontakt mit Luftsauerstoff, ist Al nur bedingt für den kathodischen Korrosionsschutz geeignet. Um die Bildung der Oxidschicht einzuschränken, muss Al legiert werden. Trotz intensiver Forschung ist die Al-Abscheidung aus ILs noch nicht gänzlich verstanden. Der Einsatz löslicher Al Anoden ist weit verbreitet, die anodische Passivierung bei hohen Stromdichten ist aber ein limitierender Faktor, dessen Ursache noch nicht eindeutig geklärt wurde. Die Abscheidung von Al Legierungen wurde intensiv untersucht, ihre Eignung für den kathodischen Korrosionsschutz unter Umgebungsbedingungen wurde allerdings noch nicht ausreichend thematisiert. In dieser Arbeit wird die Abscheidung von Al, AlCr, AlZn und AlSn aus Chloraluminat-ILs untersucht. Die Elektrodenkinetik der Al Auflösung und Abscheidung sowie die Raten bestimmenden Schritte wurden mittels zyklischer Voltammetrie (CV), Impedanzspektroskopie und Chronopotentiometrie (CP) untersucht und Reduktions bzw. Oxidationsmechanismen wurden vorgeschlagen. Mittels linearer Polarisation (LSV), elektrochemischer Quarzmikrowaage (EQCM), CV und CP konnte die Ursache anodischer Passivierung ermittelt werden. Die Wirkungsweise der Vorbehandlung von Stahl mit anodischer Polarisation in der IL wurde untersucht und die Haftungsverbesserung wurde mit der mechanischen Verzahnung der Schicht im Substrat begründet. Die Abscheidung von AlCr, AlZn und AlSn auf Stahl wurde mittels CV, EQCM, REM, EDX und XRD charakterisiert. Ihr Korrosionsverhalten wurde in Hinblick auf den kathodischen Korrosionsschutz mittels LSV, neutralem Salzsprühnebeltest (NSS Test) und Freibewitterung (EE Test) untersucht. Al und AlZn bieten hervorragenden Korrosionsschutz im NSS Test. AlCr und AlSn versagen binnen weniger Tage. Im Gegensatz zu den anderen Beschichtungen, verzögert AlZn im EE Test die Bildung von Rotrost für mehr als ein Jahr, was es zu einer vielversprechenden Alternative zu Cd macht. Die Komplexierung der Metallionen in den Elektrolyten wurde mittels RAMAN Spektroskopie und DFT aufgeklärt. Es wurde gezeigt, dass sich Komplexe der Struktur [Me(AlCl4)3]- (Me = Zn, Sn) bilden.
https://doi.org/10.22032/dbt.48729
Effects of module stiffness and initial compression on lithium-ion cell aging. - In: Journal of power sources, ISSN 1873-2755, Bd. 506 (2021), 230163
The effects of automotive-related lithium-ion module design, i.e. module stiffness and initial compression during module assembly on cell aging, swelling and pressure evolution are still largely unknown. This paper presents the results of a long-term aging study of 12 large-format automotive graphite/NMC 622 pouch cells, cycled for different module stiffnesses and initial compressions using design of experiments. Statistical analysis of mechanical and aging data revealed significant nonlinear (interaction) effects of both factors on pressure evolution, capacity loss and increase in internal resistance of the cells. Pressure dependent cell aging is observed over 1000 cycles, which was related to loss of active material at the cathode from differential voltage analysis. Post-mortem analysis confirmed a cathode active material loss via half- and full-cell measurements of harvested electrodes. Cross-section SEM micrographs revealed increasing NMC-particle cracking with higher pressure. Based on this, a fatigue-based aging model was developed to describe the capacity loss due to pressure dependent particle cracking. The presented approach enables both improved modeling of pressure dependent aging and lifetime optimized module design
https://doi.org/10.1016/j.jpowsour.2021.230163