Papers by Ulrich Stimming
Nature Communications, Apr 6, 2020
Forecasting the state of health and remaining useful life of Li-ion batteries is an unsolved chal... more Forecasting the state of health and remaining useful life of Li-ion batteries is an unsolved challenge that limits technologies such as consumer electronics and electric vehicles. Here, we build an accurate battery forecasting system by combining electrochemical impedance spectroscopy (EIS)-a real-time, non-invasive and information-rich measurement that is hitherto underused in battery diagnosis-with Gaussian process machine learning. Over 20,000 EIS spectra of commercial Li-ion batteries are collected at different states of health, states of charge and temperatures-the largest dataset to our knowledge of its kind. Our Gaussian process model takes the entire spectrum as input, without further feature engineering, and automatically determines which spectral features predict degradation. Our model accurately predicts the remaining useful life, even without complete knowledge of past operating conditions of the battery. Our results demonstrate the value of EIS signals in battery management systems.
ACS Applied Materials & Interfaces, Aug 25, 2020
Polyoxometalates (POMs) have emerged as potential anode materials for lithium-ion batteries (LIBs... more Polyoxometalates (POMs) have emerged as potential anode materials for lithium-ion batteries (LIBs) owing to their ability to transfer multiple electrons. Although POM anode materials exhibit notable results in LIBs, their energy-storage mechanisms have not been well-investigated. Here, we utilize various in operando and ex situ techniques to verify the chargestorage mechanisms of a Keplerate-type POM Na 2 K 23 {[(Mo VI)-Mo VI 5 O 21 (H 2 O) 3 (KSO 4)] 12 [(V IV O) 30 (H 2 O) 20 (SO 4) 0.5 ]}• ca200H 2 O ({Mo 72 V 30 }) anode in LIBs. The {Mo 72 V 30 } anode provides a high reversible capacity of up to ∼1300 mA h g −1 without capacity fading for up to 100 cycles. The lithium-ion storage mechanism was studied systematically through in operando synchrotron X-ray absorption near-edge structure, ex situ X-ray diffraction, ex situ extended X-ray absorption fine structure, ex situ transmission electron microscopy, in operando synchrotron transmission X-ray microscopy, and in operando Raman spectroscopy. Based on the abovementioned results, we propose that the open hollow-ball structure of the {Mo 72 V 30 } molecular cluster serves as an electron/ion sponge that can store a large number of lithium ions and electrons reversibly via multiple and reversible redox reactions (Mo 6+ ↔ Mo 1+ and V 5+ /V 4+ ↔ V 1+) with fast lithium diffusion kinetics (D Li + : 10 −9 −10 −10 cm 2 s −1). No obvious volumetric expansion of the microsized {Mo 72 V 30 } particle is observed during the lithiation/delithiation process, which leads to high cycling stability. This study provides comprehensive analytical methods for understanding the lithium-ion storage mechanism of such complicated POMs, which is important for further studies of POM electrodes in energy-storage applications.
ChemInform, Jun 14, 2005
A density functional theory database of hydrogen chemisorption energies on close packed surfaces ... more A density functional theory database of hydrogen chemisorption energies on close packed surfaces of a number of transition and noble metals is presented. The bond energies are used to understand the trends in the exchange current for hydrogen evolution. A volcano curve is obtained when measured exchange currents are plotted as a function of the calculated hydrogen adsorption energies and a simple kinetic model is developed to understand the origin of the volcano. The volcano curve is also consistent with Pt being the most efficient electrocatalyst for hydrogen evolution.
Surface Science, 2005
The stability of gold supported palladium clusters, generated with an electrochemical scanning tu... more The stability of gold supported palladium clusters, generated with an electrochemical scanning tunnelling microscope, has been investigated in metal-free electrolyte. The clusters are found to be more stable, if the tip is moved further towards the electrode surface during the generation process. Only a weak dependence of the potential on the dissolution is observed, but a strong increase of the dissolution current density with decreasing particle size. Dissolution of the clusters occurs from the edges rather than layer by layer.
ECS Transactions, 2013
not Available.
The Journal of Physical Chemistry, 1996
Tunneling and activation in reactions at interfaces may be facilitated or hampered depending on t... more Tunneling and activation in reactions at interfaces may be facilitated or hampered depending on the degree of structural ordering. "Scalar" coupling of the reaction with the system structure, independent of the sign of the order parameter, is considered. It is shown that near the temperature of a second-order phase transition such coupling can lead to a singularity of the reaction current as a function of temperature, which appears as a spike or dip in real systems. Experimental data that may be indicative of this effect are discussed.
MRS Proceedings, 2009
Metallic and non-metallic nanoparticles, usually supported on non-metallic substrates have attrac... more Metallic and non-metallic nanoparticles, usually supported on non-metallic substrates have attracted much interest concerning their application in the field of electrocatalysis. To characterize catalysts with respect to size, morphology, structure and composition (alloys or core-shell) of nanoparticles and their associated electrocatalytic activity, transmission electron microscopy (TEM) is the state of the art method. This investigation shows the advantages of advanced image processing using the local adaptive threshold (LAT) routine.
Fuel Cells, 2010
are also part of the list. In total, seven out of these ten most downloaded articles were publish... more are also part of the list. In total, seven out of these ten most downloaded articles were published in topical issues. We would thus like to say a special thank you to all the Guest Editors of both topical and special issues, for inviting and taking care of the publication of highest quality articles at the core interests of our readers.
Fuel Cells, 2007
With this sixth and last issue of the year 2007 we would like to take the opportunity to thank yo... more With this sixth and last issue of the year 2007 we would like to take the opportunity to thank you for your continuous support and all your efforts to further develop and steadily improve the scientific impact of the journal Fuel Cells-From Fundamentals to Systems. We wish to thank all the authors for submitting their excellent research work to Fuel Cells, all the referees for taking their precious time to evaluate the contributions as well as all the members of the Editorial Board and the Advisory Board for their expertise, their guidance, their enthusiasm and their help in spreading the word about the journal within our research community. Reflecting the growing success of the journal, the number of articles submitted to Fuel Cells has increased steadily in recent years. This also holds true for papers that originate from research groups in China. In order to respond to this development and to further enhance the visibility of China in the fuelcells arena, we feel very glad and honoured that Professor Liquan Chen (Institute of Physics, Chinese Academy of Sciences, Beijing) has accepted to join as a new and eminent member of the Editorial Board from 2008 onward. Please join us in welcoming Professor Chen to the Editorial Board of Fuel Cells. Fuel Cells publishes on all aspects of fuel cells, ranging from fundamental studies, materials development and characterisation to their applications in systems such as power plants, road vehicles and power sources in portables. Original Research Papers, Communications and Review articles from these areas are published in either Special Issues that are dedicated to important research topics or regular ones. Topical Issues on Novel Ceramic Materials for Fuel Cells, on Bio-Fuel Cells and on selected papers from workshops organised under the auspices of the CARISMA European Coordination Action on high-temperature membrane electrode assemblies are in the planning for 2008. We are looking forward to continuing our fruitful cooperation in 2008 and to receiving your next excellent contribution for Fuel Cells.
Thin Solid Films, 1981
The rate of electron transfer reactions at titanium electrodes covered with thin platinum-doped p... more The rate of electron transfer reactions at titanium electrodes covered with thin platinum-doped passive films was investigated. The doping enhances the current considerably. It is suggested that the platinum atoms in the film serve as intermediate states in an electronic resonance-tunnelling mechanism. The corresponding model calculations show a satisfactory agreement with the experimental data. From these calculations the energy levels of the platinum states in the film are estimated.
The Journal of Physical Chemistry B, 1997
ABSTRACT
Solid State Ionics, 2006
NH 4 PO 3 /SiO 2 composite based electrolyte with SiO 2 as supporting matrix was prepared. A ther... more NH 4 PO 3 /SiO 2 composite based electrolyte with SiO 2 as supporting matrix was prepared. A thermogravimetric analysis was performed. Its electrochemical properties were investigated by an impedance spectroscopy within the temperature range of 100-300°C under dry and humid atmospheres. The maximum conductivity is 6 mS cm − 1 at 300°C under dry N 2 and 0.1 S cm − 1 at 200°C under humid N 2 .
Solid State Ionics, 1997
The interface HgHClO4 · 5.5H2O was investigated by cyclic voltammetry and electrochemical impedan... more The interface HgHClO4 · 5.5H2O was investigated by cyclic voltammetry and electrochemical impedance spectroscopy between 170 and 300 K. In this temperature range, phase transitions occur for electrode and electrolyte, such that within 6 K the electrode-electrolyte interface changes from solid-solid over solid-liquid to liquid-liquid or vice versa. The double layer capacity was investigated as a function of potential for
Journal of Power Sources, 2006
Solid oxide fuel cells (SOFCs) have many attractive features for widespread applications. The hig... more Solid oxide fuel cells (SOFCs) have many attractive features for widespread applications. The high operating temperature provides a valuable heat source and in contrast to low temperature fuel cells they not only tolerate substances such as CO but can even use them as fuel. Thus, reforming of hydrocarbon fuels for SOFCs can be done without additional gas purification. As both stack and hydrocarbon reformer unit have to be operated at high temperatures (700-1000 • C), thermal management plays an important role in the successful operation of SOFC systems. As the SOFC system contains ceramic components, both large thermal gradients in the system and thermal expansion coefficient (TEC) mismatch must be avoided. Matching TECs is done by selecting the suitable materials. Avoiding high temperature gradients is done by selecting the right system design and control strategies. In order to achieve both, we have built a finite element simulation for a complete SOFC systems which allows to study system parameters both during steady operation and during transients. Examples of the thermal start-up behaviour for several system configurations are given for selected components as well as internal temperatures of the SOFC-stack during start-up. The simulation model includes also the option to simulate the effects of internal methane reformation in the SOFC stack. As the minimum operation temperature is high, cooling down of the system has to be avoided if instant operation is desired. This can be achieved either passively by selecting suitable thermal insulation materials and/or actively by adopting a strategy for maintaining the temperature.
Journal of Power Sources, 1998
... 221228. 2 LGJ de Haart, Th. Hauber, K. Mayer and U. Stimming, in B. Thorstensen (ed.), Proc.... more ... 221228. 2 LGJ de Haart, Th. Hauber, K. Mayer and U. Stimming, in B. Thorstensen (ed.), Proc. 2nd Eur. ... 229235. 3 HP Buchkremer, U. Diekmann, LGJ de Haart, H. Kabs, U. Stimming and D. Stöver, in U. Stimming, SC Singhal, H. Tagawa and W. Lehnert (eds.), Proc. 5th Int. ...
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Papers by Ulrich Stimming