Elucidating the transport of electrons and molecules in a solid electrolyte interphase close to battery operation potentials using a four-electrode-based generator-collector setup. - In: Journal of the American Chemical Society, ISSN 1520-5126, Bd. 146 (2024), 28, S. 19009-19018
In lithium-ion batteries, the solid electrolyte interphase (SEI) passivates the anode against reductive decomposition of the electrolyte but allows for electron transfer reactions between anode and redox shuttle molecules, which are added to the electrolyte as an internal overcharge protection. In order to elucidate the origin of these poorly understood passivation properties of the SEI with regard to different molecules, we used a four-electrode-based generator-collector setup to distinguish between electrolyte reduction current and the redox molecule (ferrocenium ion Fc+) reduction current at an SEI-covered glassy carbon electrode. The experiments were carried out in situ during potentiostatic SEI formation close to battery operation potentials. The measured generator and collector currents were used to calculate passivation factors of the SEI with regard to electrolyte reduction and with regard to Fc+ reduction. These passivation factors show huge differences in their absolute values and in their temporal evolution. By making simple assumptions about molecule transport, electron transport, and charge transfer reaction rates in the SEI, distinct passivation mechanisms are identified, strong indication is found for a transition during SEI growth from redox molecule reduction at the electrode | SEI interface to reduction at the SEI | electrolyte interface, and good estimates for the transport coefficients of both electrons and redox molecules are derived. The approach presented here is applicable to any type of electrochemical interphase and should thus also be of interest for interphase characterization in the fields of electrocatalysis and corrosion.
https://doi.org/10.1021/jacs.4c03029
State of health estimation for second life lithium-ion batteries: indicators and considerations. - In: IEEE Xplore digital library, ISSN 2473-2001, (2024), insges. 6 S.
This study aims to provide valuable insights into state of health estimation of second-life lithium-ion batteries in stationary energy storage systems by conducting an analytical examination of key technical indicators and considerations. By considering these factors, we can enhance our understanding of the estimation process and make informed decisions regarding the conditions of utilizing these batteries in their second life. The approach, presented in this paper, focuses on two main aspects. Firstly, it takes into account the unique characteristics of these batteries, which exhibit different responses to operational factors compared to their initial life cycle in electrical vehicles. Secondly, it considers monitoring conditions of stationary storage systems to develop an enhanced monitoring system which leads to an efficient performance of batteries in their second-life. By addressing these aspects, we aim to optimize the utilization of second-life batteries in stationary storage systems and ensure their reliable operation. This methodology, which utilizes Kalman filter and empirically derived data, has demonstrated significantly improved reliability and accuracy compared to other methodologies. By leveraging Kalman filter, we were able to enhance the estimation process and achieve a more precise estimation of state of health in stationary energy storage systems.
https://doi.org/10.1109/SPECon61254.2024.10537480
A bright future for electrodeposition. - In: The Electrochemical Society interface, ISSN 1944-8783, Bd. 33 (2024), 2, S. 45-46
The Electrodeposition Division, which was founded in 1922 as the second ECS division, celebrated their centennial anniversary at the 242nd ECS Fall meeting in Atlanta. For the occasion, the division organized several sessions with invited contributions to honor the achievements of 100 years of electrodeposition, but also to take a closer look at the present trendsetters and give a perspective on future challenges and opportunities in this thriving field. Our then newly established Electrodeposition Early Career Forum (ECF, founded in Spring 2022) organized a full day symposium with contributions from outstanding early-career researchers involved in cutting-edge research across a broad range of areas of active electrodeposition research. It turned out to be a fantastic day with invigorating talks full of ideas. The ELDP division decided to share some of the excitement with the ECS community and asked our ECF members to suggest topics and participate in the articles for this summer edition of Interface dedicated to Electrochemical and Electroless deposition. Dr. Kent Zheng, assistant professor at the University of Texas and Dr. Martin Leimbach, postdoc at TU Ilmenau, Germany, took up the challenge. Together with us, humble guest editors, four articles have been selected centred around three important topics: (1) electrodeposition for manufacturing and sustainability, edited by Prof. Luca Magagnin; (2) electrodeposition for energy applications, edited by Prof. Natasa Vasiljevic; and (3) new electrodeposition approaches extending the material library, edited by Prof. Philippe Vereecken.
https://doi.org/10.1149/2.F08242IF
Advancements in electrodeposition for precise manufacturing and sustainability. - In: The Electrochemical Society interface, ISSN 1944-8783, Bd. 33 (2024), 2, S. 47-54
Simply expressed, the circular economy implies that the people living on Earth should reuse and recycle the products that are currently in use as long as possible and reduce the waste produced, thus reducing CO2 emissions. The latter goal is fundamental from the perspective of mitigating the well-known greenhouse effect and the consequent global warming observed at the planetary scale. Under these conditions, advanced electrodeposition processes can play a fundamental role in the optimization of materials use and in the reduction of the energetic footprint for a wide variety of industrial processes. The aim of the present paper is precisely to suggest how this is possible, showing readers the potential that electrodeposition holds for efficient manufacturing of many different products that have a huge significance for industry.
https://doi.org/10.1149/2.F09242IF
Investigating the suitability of various silver(I) complexes for use in a cyanide-free silver electrolyte. - In: Coatings, ISSN 2079-6412, Bd. 14 (2024), 5, 618, S. 1-16
The suitability of various nitrogen, sulfur, oxygen, and phosphorus compounds as complexing agents in a silver electrolyte was examined by using potentiometric titration under practical conditions. The setup consisted of three electrodes to measure the pH and the activity of the silver ions simultaneously. Different ratios of silver to complexing agent from 1:10 to 1:1 at a constant ionic strength of 0.2 mol/L were investigated. The type of the complexes and their corresponding critical stability constants were evaluated by fitting the measured data using a self-developed algorithm. The pH and Nernst potential curve were calculated for the assumed complexes based on the law of mass action to find the best approximation. The correct definition of the occurring species is challenging and can lead to significant changes in the calculation of stability constants. For this reason, the measured silver potential curves were primarily used for the rating of the complexing agents. An evaluation of the measurements shows that the donor atom of the complexing agent and its ligand field strongly affected the stability and type of the complexes. Only a few complexing agents were found to be suitable for use in the cyanide-free silver electrolyte.
https://doi.org/10.3390/coatings14050618
A novel method for preparation of Al-Ni reactive coatings by incorporation of Ni nanoparticles into an Al matrix fabricated by electrodeposition in AlCl3:1-eethyl-3-methylimidazolium chloride (1.5:1) ionic liquid containing Ni nanoparticles. - In: Advanced engineering materials, ISSN 1527-2648, Bd. 0 (2024), 0, 2302217, S. 1-17
Al/Ni reactive coatings are fabricated via electrochemical deposition (ECD) at different applied voltages for reactive bonding application. AlCl3:1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) (1.5:1) ionic liquid electrolyte is used as source of Al, whereas Ni is in the bath and incorporated into final coatings as nanoparticles (NPs). Scanning electron microscopy and Auger electron spectroscopy reveal a homogeneous Ni particle dispersion, as well as a high amount of particle incorporation into the Al matrix. A maximum of 37 wt% (22 at%) of Ni is detected via atomic absorption spectroscopy in the Al/Ni coating deposited at −0.1 V from an electrolyte containing 20 g L−1 of Ni NPs. Previous literature show that for bonding application an ideal concentration is around 50 at% of Ni and 50 at% Al. However, this is achieved using high vacuum, time-consuming processes, and costly techniques like evaporation and magnetron sputtering. The ECD used in this work represents a more cost-efficient approach which is not reported up to date for the aforementioned application. The reactivity of the coatings is confirmed by Differential scanning calorimetry. Herein, an exothermic reaction is detected upon the mixing of Al and Ni occurring at high temperatures.
https://doi.org/10.1002/adem.202302217
Integration of multijunction absorbers and catalysts for efficient solar-driven artificial leaf structures: a physical and materials science perspective. - In: Solar RRL, ISSN 2367-198X, Bd. 8 (2024), 11, 2301047, S. 1-49
Artificial leaves could be the breakthrough technology to overcome the limitations of storage and mobility through the synthesis of chemical fuels from sunlight, which will be an essential component of a sustainable future energy system. However, the realization of efficient solar-driven artificial leaf structures requires integrated specialized materials such as semiconductor absorbers, catalysts, interfacial passivation, and contact layers. To date, no competitive system has emerged due to a lack of scientific understanding, knowledge-based design rules, and scalable engineering strategies. Here, we will discuss competitive artificial leaf devices for water splitting, focusing on multi-absorber structures to achieve solar-to-hydrogen conversion efficiencies exceeding 15%. A key challenge is integrating photovoltaic and electrochemical functionalities in a single device. Additionally, optimal electrocatalysts for intermittent operation at photocurrent densities of 10-20 mA cm^-2 must be immobilized on the absorbers with specifically designed interfacial passivation and contact layers, so-called buried junctions. This minimizes voltage and current losses and prevents corrosive side reactions. Key challenges include understanding elementary steps, identifying suitable materials, and developing synthesis and processing techniques for all integrated components. This is crucial for efficient, robust, and scalable devices. Here, we discuss and report on corresponding research efforts to produce green hydrogen with unassisted solar-driven (photo-)electrochemical devices. This article is protected by copyright. All rights reserved.
https://doi.org/10.1002/solr.202301047
Modelling reaction transfer velocities in disconnected compact heterogeneous multilayer reactive material systems. - In: MRS advances, ISSN 2059-8521, Bd. 0 (2024), 0, S. 1-6
The tuning of the self-propagating reaction is studied theoretically by introducing a non-reactive material between two reactive material elements. For the study, the Ni/Al bilayer system was chosen. The Ni/Al elements were placed on a silicon wafer covered with a 1-µm-thick silicon dioxide. The spaces between the multilayer reactive material elements were filled with different non-reactive materials covering a wide range of thermal properties. On top of this heterogeneous layer, a 1-µm-thick sealing layer was placed consisting of the filler material. The carried out two-dimensional simulations demonstrated that embedding material allows to scale the ignition transfer time and the heat propagation velocity. For example, for a transfer length of 1 µm, the ignition time can be tuned from nano- to microseconds. Consequently, in contrast to previous results embedding materials allow scaling the properties of the self-propagating reaction in heterogeneous reactive material systems.
https://doi.org/10.1557/s43580-024-00822-3
Improved approach for online monitoring of second life lithium-ion batteries to optimize the performance in stationary storage systems. - In: 2023 14th International Renewable Energy Congress (IREC), (2024), insges. 6 S.
Monitoring lithium-ion batteries in their second life is of great importance when using them in stationary storage systems for grid support or in any other energy system, due to the expected different behavior and operational conditions in their second life compared to their first life. The idea of this study based on the fact that each estimation method has its advantages and drawbacks depending on the application in which the batteries will be used, and that monitoring batteries in their second life required to be integrated with the battery management system to balance cells, optimize performance, and prevent overheating. The contribution of our study can be summarized in the integration of specific methods, aiming to benefit from most of their advantages and neutralizing their drawbacks as much as possible to provide more accurate and reliable online monitoring of batteries. The combination presented in this study, consisting, for state of charge estimation, of an artificial neural network and an Unscented Kalman Filter with adjusting the filtering process using Coulomb counting, and Kalman Filter for state of health estimation, showed much better reliability and accuracy than if each method was used alone. This combination has been trained and adjusted using empirical data of second-life batteries, extracted from used electric vehicle battery bank, to obtain the best possible performance, considering the specificity of these batteries in terms of operating voltage range, lower current ratio, and other parameters.
https://doi.org/10.1109/IREC59750.2023.10389283
Electrochemical reduction of tantalum and titanium halides in 1-butyl-1-methylpyrrolidinium bis (trifluoromethyl-sulfonyl)imide and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ionic liquids. - In: Journal of solid state electrochemistry, ISSN 1433-0768, Bd. 28 (2024), 5, S. 1557-1570
The electrodeposition of tantalum-titanium–based films using different tantalum and titanium halides was investigated in two ionic liquids, namely, 1-butyl-1-methylpyrrolidinium bis (trifluoromethyl-sulfonyl)imide ([BMP][TFSI]) and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([BMP][OTf]). Cyclic voltammetry was used to analyse the electrochemistry of the electrolytes and potentiostatic deposition was performed to evaluate the feasibility of electrodepositing tantalum-titanium–based layers. Both the metal salts and the ionic liquid influenced the electrochemical reduction of the tantalum and titanium halides significantly. While titanium halides considerably retarded the reduction of tantalum pentahalides and inhibited electrodeposition in many electrolytes, an electrolyte composition from which tantalum and titanium-containing layers could be deposited was identified. Specifically, in TaBr5 and TiBr4 in [BMP][TFSI], TiBr4 did not inhibit the deposition of tantalum and titanium was co-deposited itself by a three-step reduction mechanism as confirmed by cyclic voltammetry and energy-dispersive X-ray spectroscopy. Furthermore, [BMP][TFSI] led to smoother and more compact deposits.
https://doi.org/10.1007/s10008-023-05773-7