Publications Search Results

Now showing 1 - 10 of 11
  • Publication
    Investigation of the temperature dependence of lithium plating onset conditions in commercial Li-ion batteries
    ( 2019)
    Angeles Cabañero, Maria
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    Altmann, Johannes
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    Boaretto, Nicola
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    Müller, Jana
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    Hein, Simon
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    Kallo, Josef
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    Latz, Arnulf
    Fast charging is one of the main challenges in Lithium-ion battery applications. Especially at low temperatures and high C-rates, capacity loss due to lithium plating is identified as the main aging effect. Electrochemical models are able to predict the lithium plating onset conditions, as they provide information about the local potentials and lithium concentrations within the individual electrodes. Due to the narrow potential window of graphite, a precise determination of the sensitive parameters is needed for an accurate prediction of the plating onset. Experimental parameterization is needed as each cell has a specific geometry and the transport parameters are material and geometry-dependent. Literature values are scattered and often do not provide information on the electrode geometry. In this study, a non-isothermal electrochemical 3D model was experimentally parameterized and used to investigate the lithium plating onset at low temperatures. The whole set of geometrical, transport and kinetic model parameters were determined at different temperatures and states of charge and the results were validated against the individual potentials of a multi-layer pouch cell. Good predictions of lithium plating onset were obtained. The study shows that the model can be used to develop fast-charging strategies for commercial lithium-ion batteries at low temperatures.
  • Patent
    Elektrochemische Zelle mit Komponenten aus einem organisch-anorganischen Hybridmaterial und weitere Verwendungen dieses Hybridmaterials
    ( 2019)
    Boaretto, Nicola
    Erfindungsgemäß wird eine elektrochemische Zelle mit einer ersten und einer zweiten Elektrode, einem Elektrolyten, mindestens einer Schutz- oder Zwischenschicht und gegebenenfalls einem Separator, wobei mindestens eine der Komponenten der elektrochemischen Zelle aus einem anorganisch-organischen Hybridmaterial gebildet ist. Darüberhinaus wird vorgeschlagen, ein anorganisch-organisches Hybridmaterial als Bestandteil in elektrochemischen Zellen und als Beschichtungsmaterial für Bestandteile in elektrochemischen Zellen zu verwenden. Insbesondere können die Elektroden, der Elektrolyt, der Separator oder die Schutz- oder Zwischenschichten mit dem anorganisch-organischen Hybridmaterial ausgestattet bzw. beschichtet werden.
  • Publication
    Direct determination of diffusion coefficients in commercial Li-ion batteries
    ( 2018)
    Cabañero, Maria Angeles
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    Boaretto, Nicola
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    Röder, Manuel
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    Müller, Jana
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    Kallo, Josef
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    Latz, Arnulf
    Diffusion coefficients are important parameters for the characterization of new electrode materials, but they are also essential for the study of cell aging and as input parameters in battery modeling. In this report, the applicability of the galvanostatic intermittent titration technique (GITT) on commercial cells is studied. A GITT protocol is applied on a set of commercial cells with graphite anodes and various cathode materials. The cell response is then compared with the ones of the individual electrodes, obtained in three-electrode and half-cell configurations. In particular, mostly due to the particular potential profile of graphite, the full cell GITT response corresponds to the anode and cathode response at low and high state of charge, respectively. Therefore, it is possible to estimate the diffusion coefficients of the individual electrodes by a simple experiment on commercial cells, although only in limited ranges of SOC. If the experiments are performed at different temperatures, it is also possible to determine the activation energies of the diffusion coefficients. In conclusion, GITT allows an estimation of the diffusivity data in commercial cells, and can be therefore used as fast analytical tool for the study of aging and for the modeling of lithium-ion batteries.
  • Publication
    Optimization of the transport and mechanical properties of polysiloxane/polyether hybrid polymer electrolytes
    ( 2017)
    Boaretto, Nicola
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    Horn, Theresa
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    In this study, the thermo-mechanical properties of networked, polysiloxane/polyether-based, hybrid polymer electrolytes are optimized with the aim of enabling room-temperature operation in lithium metal-polymer batteries. The structural parameters of the electrolytes (polyether chain length, cross-linking and salt concentration) are varied in order to get the best tradeoff between conductivity and mechanical stability. The optimized material has a conductivity close to 1.5·10−4 S cm−1 at room temperature and a shear storage modulus of 50 kPa up to 100 °C. The effect of TiO2 nano-particles is also studied with the results showing an overall ambiguous effect on the materials properties. Finally, one of the materials with the highest conductivity is used as electrolyte in a Li/LiFePO4 cell. This cell has good rate capability and cyclability due to the high conductivity of the electrolyte. However, the high conductivity is reached at expense of the mechanical stability and the resulting electrolyte proves to be too weak to work as an efficient barrier against lithium dendrite growth.
  • Publication
    Inorganic-organic hybrid polymer electrolytes for secondary lithium metal batteries
    ( 2016)
    Boaretto, Nicola
    Polymer electrolytes are an important class of ionic conducting materials, which find application essentially in electrochemical storage devices, such as secondary lithium batteries or fuel cells. Regarding the application in lithium batteries, the interest on polymer electrolytes arises primarily from their inherent safety, at least in comparison with classical liquid electrolytes. Furthermore, polymer electrolytes show higher compatibility with lithium metal. The use of lithium metal as anode material allows a reduction of the total cell mass and thus an increase of its specific energy. This study describes the synthesis and the physical properties of polysiloxane/polyether-based hybrid polymer electrolytes. The structural, thermo-mechanical, electrochemical and transport properties of the hybrid electrolytes are characterized by means of several analytical techniques. Finally, the performances of lithium-metal polymer batteries with the best performing materials are analyzed. An attempt to enhance the cycling life of these cells by passivation of the lithium electrodes is also described. The materials are synthesized by sol-gel reaction of functionalized alkoxysilanes and by polymerization of vinyl or epoxide functionalities. The synthesized hybrid polymer electrolytes show good ionic conductivities (up to 8∙10-5 SBLcm-1 at room temperature), and high thermo-mechanical and electrochemical stabilities. Broadband electric spectroscopy analysis (BES) shows that the ionic mobility is maximized if a) short-range ion-ion interactions are negligible and b) ordered stacking of the polyether chains is hindered. If both conditions are satisfied, the charge motion is modulated by the segmental motion of the polyether chains. Full cell tests at 60 °C show that these materials can be used as electrolytes in lithium metal batteries, even though a moderate capacity fade upon cycling is observed. This is attributed, among other factors, to contact and electrochemical stability issues between lithium and electrolyte. Pre-coating of the Lithium surface with cyclic carbonates, or the introduction of a softer electrolyte as buffer, helps preventing electrolyte degradation and improving the performance and cycling life of Li-metal polymer cells.
  • Publication
    Conductivity and properties of polysiloxane-polyether cluster-LiTFSI networks as hybrid polymer electrolytes
    ( 2016)
    Boaretto, Nicola
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    Joost, Christine
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    Seyfried, Mona
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    Vezzu, Keti
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    Noto, Vito di
    This report describes the synthesis and the properties of a series of polymer electrolytes, composed of a hybrid inorganic-organic matrix doped with LiTFSI. The matrix is based on ring-like oligo-siloxane clusters, bearing pendant, partially cross-linked, polyether chains. The dependency of the thermo-mechanic and of the transport properties on several structural parameters, such as polyether chains' length, cross-linkers' concentration, and salt concentration is studied. Altogether, the materials show good thermo-mechanical and electrochemical stabilities, with conductivities reaching, at best, 8·10−5 S cm−1 at 30 °C. In conclusion, the cell performances of one representative sample are shown. The scope of this report is to analyze the correlations between structure and properties in networked and hybrid polymer electrolytes. This could help the design of optimized polymer electrolytes for application in lithium metal batteries.
  • Publication
    Property-Relaxation Correlations in 3D-Siloxane/Polyether Hybrid Polymer Electrolytes
    ( 2016)
    Boaretto, Nicola
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    Joost, Christine
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    Vezzu, Keti
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    Pace, Giuseppe
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    Noto, Vito di
  • Publication
    Hybrid polymer electrolytes based on linear siloxane networks and crosslinked polyether domains: Interplay between composition and properties
    ( 2015)
    Boaretto, Nicola
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    Brinkmann, Christine
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    Vezzu, Keti
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    Noto, Vito di
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    In this study, a new class of hybrid polymer electrolytes was prepared and characterized. The materials consisted of a matrix based on linear oligosiloxane networks and partially crosslinked polyether domains, doped with Lithium bis(trifluorosulfonyl)imide (LiTFSI). These materials are characterized by a maximum conductivity of 8∙10-5 S/cm at 30 °C, and high thermo-mechanical stability, with decomposition temperature of 250 °C and a storage shear modulus of almost 105 Pa at 100 °C. Compositional parameters such as salt, cross-linker concentration, and polyether chain length were varied, and the materials were characterized by several analytical techniques. Vibrational spectroscopy provided details of the hybrid structure and the effect of salt doping. The thermo-mechanical properties were studied by thermogravimetric analysis, differential scanning calorimetry and rheological analysis. Finally, the transport properties were analyzed by means of broadband electric spectroscopy. The study made it possible to describe the relationships between composition, morphology, thermo-mechanical and transport properties of the synthesized hybrid electrolytes, with particular emphasis on the interplay between polymer dynamics and conduction mechanism.
  • Patent
    Elektrochemische Zelle mit einem organisch-anorganischen Hybridmaterial und Verwendung eines anorganisch-organischen Hybridmaterials
    ( 2015)
    Brinkmann, Christine
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    Seyfried, Mona
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    Boaretto, Nicola
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    Bünsow, Johanna
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    Erfindungsgemäss wird eine elektrochemische Zelle mit zwei Elektroden und einem Elektrolyten bereitgestellt, wobei mindestens eine der Komponenten der elektrochemischen Zelle ein anorganisch-organisches Hybridmaterial aufweist. Darüberhinaus wird vorgeschlagen ein anorganisch-organisches Hybridmaterial als Bestandteil in elektrochemischen Zellen und als Beschichtungsmaterial für Bestandteile in elektrochemischen Zellen zu verwenden. Insbesondere können Elektrolyt, Elektrodenmaterial und Separatoren mit dem anorganisch-organischen Hybridmaterial ausgestattet bzw. beschichtet werden. Das anorganisch-organische Hybridmaterial kann auch als Binder in elektrochemischen Zellen eingesetzt werden. Für bestimmte Anwendungen kann das anorganisch-organische Hybridmaterial mit einem Leitsalz, insbesondere einem Lithium-Leitsalz, kombiniert werden.; Das Hybridmaterial zeichnet sich dadurch aus, dass es chemisch kovalent vernetzt werden kann.